Synthesis of Cyanuric Acid and Hamilton Receptor Functionalized … · 2013-09-03 · and...

Synthesis of Cyanuric Acid and Hamilton Receptor

Functionalized Tetraphenylporphyrins:

Investigation on the Chiroptical and Photophysical Properties of

their Self-assembled Superstructures with Depsipeptide and

Fullerene Dendrimers

Den Naturwissenschaftlichen Fakultäten der Friedrich-

Alexander-Universität Erlangen-Nürnberg

zur

Erlangung des Doktorgrades

vorgelegt von

Katja Maurer-Chronakis

aus Nürnberg

Als Dissertation genehmigt von den Naturwissenschaftlichen Fakultäten der

Friedrich-Alexander Universität Erlangen-Nürnberg

Tag der mündlichen Prüfung: 19.11.2010

Vorsitzender der Promotionskomission: Prof. Dr. R. Fink

Erstberichterstatter: Prof. Dr. A. Hirsch

Zweitberichterstatter: Prof. Dr. W. Bauer

Meinem Doktorvater, Prof. Dr. A. Hirsch, gilt mein besonderer Dank für sein reges

Interesse am Fortgang dieser Arbeit sowie für seine Anregungen und die

Diskussionen mit ihm.

Die vorliegende Arbeit entstand in der Zeit von Oktober 2004 bis Juni 2010 am

Institut für Organische Chemie der Friedrich-Alexander-Universität Erlangen-

Nürnberg

Meiner Familie

„Phantasie ist wichtiger als Wissen, denn Wissen ist begrenzt”

Albert Einstein

I

1. INTRODUCTION 1 1.1 Supramolecular Chemistry-Principles and History 1 1.1.1 The History and Applications of the Hamilton Receptor

Bonding Motif 2

1.2 Non-covalent Supramolecular Porphyrin Assemblies 10 1.2.1 Synthetic Systems Mimicking Photosynthesis 11

1.2.2 Sensing of Chirality 18

2. PROPOSAL 21 3. RESULTS AND DISSCUSION 23

3.1 Synthesis of the Hamilton Receptor Derivatives 23 3.2 Synthesis of the Porphyrin Precursors 24 3.3 Synthesis and Characterization of the Porphyrin Derivatives 25

3.3.1 Synthesis of the Porphyrin Derivatives 25

3.3.2 Synthesis and Characterization of the Zinc-porphyrins 31

3.4 Synthesis and Characterization of the Zinc Porphyrins Bearing Hamilton Receptor or Cyanuric Acid Functionalities 40

3.4.1 Synthesis of a Four-fold Hamilton Receptor Functionalized

Porphyrin via an Esterification Reaction 40

3.4.2 Synthesis of the Trans- and Cis-configured Zinc Porphyrins

Bearing Hamilton Receptor or Cyanuric Acid Functionalities 45

3.4.3 Synthesis of a Four-fold Hamilton Receptor Functionalized

Porphyrin via the SONOGASHIRA C-C Coupling Reaction 58

3.4.4 Synthesis of a Four-fold Cyanuric Acid Functionalized

Porphyrin 61

3.5 Supramolecular Chiral Porphyrin Dendrimers Based on the Hamilton Receptor Bonding Motif 64 3.6 Synthesis and Photophysical Properties of Novel Supramolecular Porphyrin-Fullerene Dendrimers 86

4.SUMMARY AND CONCLUSIONS 94

II

5. ZUSAMMENFASSUNG UND ERGEBNISSE 97 6. EXPERIMENTAL PART 101 6.1 Instruments and Methods 101

6.2 Chemicals 102 6.3 Experimental Details 102 7. LITERATURE 137

III

Index of Abbreviations

AcOH Acetic acid

AFM Atomic Force Microscopy

BF3•OEt2 Boron trifluoride diethyl etherate

br Broad singlet

CS2 Carbon disulfide

CBZ Benzyloxycarbonyl

COSY Correlated Spectroscopy

d doublet

dd doublet doublet

CD Circular Dichroism

CH2Cl2 Dichloromethane

CHCl3 Chloroform

CT Charge Transfer

DCC N,N-dicyclohexylcarbodiimide

DCU Dicyclohexylurea

DCTB Trans-2-[3-(4-tert-butylphenyl)2-methyl-2-

propinylidene]malonotrile

DDQ 2,3-Dichloro-5,6-dicyano-p-benzoquinone

DHTB 2,5-Dihydroxy-benzoic acid

DIT Dithranol

DMAP 4-(Dimethylamino)pyridine

DMF Dimethylformamide

DMSO Dimethylsulfoxide

EA Elemental analysis

EDC 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide

EtOAc Ethyl acetate

EtOH Ethanol

equiv. Equivalent

FAB Fast Atom Bombardment

GPC Gel Permeation Chromatography

h hour

IV

HETCOR Heteronuclear Correlated Spectroscopy

HPLC High Performance Liquid Chromatography

IR Infrared Spectroscopy

IPCE Incident Photon to Converted Electron Efficiency

ITO Indium Tin Oxide

m multiplet

MALDI Matrix Assisted Laser Desorption Ionization

MeOH Methanol

MS Mass Spectrometry

NBA 3-Nitro-benzylalcohol

NEt3 Triethylamine

NMR Nuclear Magnetic Resonance

ODCB ortho-Dichlorbenzene

PFG Pulsed Field Gradient

ppm Parts per million

POPAM Poly-(propyleneamine)

s singlet

SIN Sinapinic acid

SOCl2 Thionyl chloride

t triplet

TFA Trifluoroacetic acid

THF Tetrahydrofuran

TLC Thin Layer Chromatography

TPP Tetraphenylporphyrin

UV/Vis Ultraviolet/Visible Spectroscopy

Zn Zinc

INTRODUCTION

1

1. INTRODUCTION

1.1. Supramolecular Chemistry - Principles and History

Supramolecular chemistry[1,2] is often termed as “the chemistry beyond the

molecule”[3] and describes the spontaneous self aggregation (self-assembly) between

molecules and/or ions by non-covalent bonding interactions. These interactions

include electrostatic Coulomb or donor-acceptor interactions, van der Waals forces,

hydrophobic forces, π-π-interactions and hydrogen bonding. Dynamic covalent

chemistry, representing an important part of supramolecular chemistry, becomes

relevant if the supramolecular structure is stabilized through the formation of

reversible covalent bonding interactions under conditions of equilibrium control.[4] On

the contrary, in terms of non-covalent supramolecular chemistry the formation of the

thermodynamically most stable supramolecular structure is favored. However, the

dynamic character of these systems is reflected in the continuous self-assembly and

disassembly processes and therefore, the entire supramolecular aggregate exhibits

beneficial abilities like self-repair or ligand exchange reactions. Furthermore, the

relatively easy synthesis and purification of the monomeric building blocks compared

to their corresponding supramolecular self-aggregates display additional advantages.

On the other hand, the non-covalent supramolecular approach demands a very

careful design of the monomeric building blocks to ensure the self-assembly into a

specific, desired supramolecular aggregate. Generally, this can be achieved by a fine

tuning of the geometrical requirements of the host and guest molecules and/or by

equipping the monomers with specific non-covalent binding sites following the

molecular recognition principle. The latter was first introduced as the “lock and key”

principle for the specific interactions between enzymes and substrates by Nobel

laureate HERMANN EMIL FISCHER, in 1894.[5] In 1967, the molecular recognition

principle was successfully introduced for the template directed synthesis of crown

ethers by CHARLES JOHN PEDERSEN.[6] The following years, investigations on the

selective binding of alkali metals in cryptands were published[7,8,9] and further

development of the molecular recognition principle led to the establishment of host-

guest chemistry by DONALD JAMES CRAM.[10] In 1978, the term “Supramolecular

Chemistry” was introduced by JEAN-MARIE LEHN[11] and for their valuable contribution

INTRODUCTION

2

in this area, CRAM, LEHN and PEDERSEN were awarded the Nobel Prize in chemistry

in 1987.

Figure 1: Noncovalent self-assembly between calix[4]arene dimelamine molecules and

cyanuric acid derivatives.[12]

1.1.1. The History and Applications of the Hamilton Receptor Bonding Motif

The great importance of hydrogen bonding in nature is clearly demonstrated in the

diversity of biological supramolecular assemblies based upon these interactions, e.g.

the highly specific association of the corresponding nucleobases in the double helix

structures of DNA and RNA.[13,14] As illustrated in Figure 2b, the double helix of DNA

is stabilized via hydrogen bonding interactions between the two strands realized by

complementary pairing between adenine-thymine and guanine-cytosine bases.

INTRODUCTION

3

Figure 2: a) Helical structure of A- and B-DNA; b) Base pairs connected via intermolecular

hydrogen bonding.[15]

As a consequence, the synthesis and investigation of hydrogen-bonded self-

assemblies have attracted great research interest in supramolecular chemistry.

In 1988, ANDREW D. HAMILTON published the synthesis of a macrocyclic H-bonding

receptor (Fig. 3, blue structure) and the selective complexation of barbiturate

derivatives (2) which was verified by 1H NMR titration experiments.[16] In general,

barbiturates are used as sedatives, hypnotic agents, injectable narcotics and

anticonvulsants. The Hamilton receptor consists of an isophthaloyl fragment

connected with two 2,6-diaminopyridine units via amide linkages (Fig. 3). The

selective complexation of barbiturates and cyanurates is

realized on the complimentary pairing of 2,6-

diamidopyridines and cyclic imides while the necessary

organization and rigidity is ensured by the isophthaloyl

fragment. The complexation of the guest molecule

occurs via six intermolecular hydrogen bonds in the

cavity of the Hamilton receptor and usually,

supramolecular systems based on the Hamilton

receptor bonding motif reveal considerably high

association constants in the range of 105 - 106 M-1.

Figure 3: The Hamilton receptor complex with barbiturate derivatives[16]

INTRODUCTION

4

Furthermore, open chain and macrocyclic Hamilton receptor derivatives were

exploited for the synthesis of photoactive supramolecular self-assemblies mimicking

natural photosynthetic systems.[17,18] The self-assembly between porphyrin

barbiturate 3 and a Hamilton receptor derivative equipped with a dansyl functionality

was confirmed by fluorescence titration experiments.

Figure 4: Self-assembly of porphyrin barbiturate 3 and open chain Hamilton receptor

functionalized dansyl derivative 4.[17]

Figure 5 displays a macrocyclic Hamilton receptor derivative equipped with a

porphyrin moiety. Supramolecular aggregates between 5 and barbiturates 2 were

studied as “artificial enzyme-substrate” models to

reproduce the recognition and catalytic properties of

barbiturate induced P-450. The cytochromes P-450

were found to play an important role in the hepatic

detoxification and the metabolism of drugs (e.g.

Phenobarbital). Upon complexation, the Hamilton

receptor derivative 5 “locked” the barbiturate above

the plane of the porphyrin ring thus, mimicking the

substrate binding pocket of P-450. Figure 5: P-450 mimicking self-

assembly.[18]

In 1994, HAMILTON succeeded in the enhanced extraction of Phenobarbital from

human serum using an open chain Hamilton receptor derivative.[19] LEHN utilized this

recognition motif for the synthesis of supramolecular linear and cross-linked polymers

INTRODUCTION

5

and introduced receptor molecules bearing multiple Hamilton receptor or cyanuric

acid recognition sites.[20] The linear and cross-linked supramolecular polymers

formed via the self-assembly of the Hamilton receptor derivatives 6 or 7 with the

cyanurates 8 and 9 were investigated by 1H NMR experiments.

Figure 6: Schematic representation of the supramolecular polymers formed via self-assembly

of the Hamilton receptors 6 and 7 and the cyanurates 8 and 9.[20]

Mixing of stoichiometric amounts of the bis-Hamilton receptor 6 and the cyanuric

biswedge 8 resulted in the formation of a supramolecular [6:8]n polymer while, upon

INTRODUCTION

6

combining the tritopic Hamilton receptor derivative 7 and 8 in a 1:1.5 molar ratio led

to the formation of a supramolecular [7:81.5]n network.

The 1H NMR spectrum of the polymeric network of [7:81.5]n in C2D2Cl4 showed very

broad and unresolved resonances but upon the addition of monotopic cyanurate 9, a

significant sharpening of the signals was observed pointing to a successful end

capping of the network. Furthermore, addition of the tritopic receptor 7 to a solution of

[6:8]n resulted in a higher degree of cross-linking observed by an increased

broadening of the NMR signals.

The attachment of the Hamilton receptor functionality to the periphery of

poly(propylenamine) dendrimers and the examination of their photophysical

properties provided decisive insights into the aggregation behavior of Hamilton

receptor derivatives bearing multiple recognition sites.[21] Generally, the Hamilton

receptor functionality features an absorption maximum at 303 nm and an emission

maximum at 461 nm.[17]

Figure 7: Schematic representation of the Hamilton receptor dendrimers 11 - 14 and the

monotopic receptor 10.[21]

The different generation dendrimers were examined by means of UV/Vis

spectroscopy and the linear increase of the molar extinction coefficient was found to

be related to the number of Hamilton receptor functionalities present in the

dendrimers. The emission spectra of the dendrimers 11 - 14 were recorded at the

characteristic wavelength of 310 nm and revealed a dual emission with a maximum

at 440 nm and a shoulder at around 500 nm. Excitation of 10 gave rise to a similar

emission spectrum with the exception of an additional band at 540 nm and a much

lower emission intensity. The quantum yields of emission were found to increase with

INTRODUCTION

7

larger generation numbers and this effect was attributed to inter- or intramolecular

aggregation processes of the peripheric Hamilton receptor functionalities. In solutions

with low concentrations intramolecular processes are expected to be predominant.

Intramolecular aggregation introduces rigidity to the Hamilton receptor derivative and

thereby, a higher quantum yield of emission was observed as a consequence of

reduced radiationless deactivation.

Figure 8: Absorption (a) and emission (b) spectra (λexc = 310 nm) of 10 - 14 in CHCl3.[21]

Further photophysical investigations of these systems resulted in the assumption of

three possible conformations for the Hamilton receptor functionalities, namely, cis-

cis, cis-trans and trans-trans with respect to the aryl-CO bonds. Upon complexation

of the barbiturate/cyanurate guest, the receptor is forced into the inplane cis-cis

conformation accompanied by the subsequent breakage of the

intramolecular/intermolecular aggregation.

INTRODUCTION

8

Figure 9: The configuration isomers of the Hamilton receptor functionality.

The homotritopic Hamilton receptor derivative 7 was employed for the first complete

self-assembly of supramolecular dendrimers based on non-dendritic subunits.[22]

The supramolecular 1:3 complexes of homotritopic receptor 7 with the cyanurate

derivatives 16 - 20 linked via variable spacers with first to third generation FRÉCHET

dendrons were investigated by 1H NMR titration experiments.

Figure 10: Schematic representation of the supramolecular building blocks.[22]

INTRODUCTION

9

Furthermore, the core unit 7 was mixed with the branching element 15 and the end

cap cyanurate 19, in a ratio of 7:(19x15n-7):(19x15n). Pulsed field gradient (PFG)

NMR spectroscopy and AFM investigations indicated the formation of discrete

dendrimers as shown in Figure 11.

Figure 11: Supramolecular self-assembly of discrete dendrimers.[22]

Another interesting application of the Hamilton recognition motif can be found in the

area of new materials science. BINDER succeeded in the defined attachment of

nanoparticles (barbituric acid derivatives fixed to Au surfaces) onto planar surfaces

via self-assembly processes using Hamilton receptor functionalized telechelic

poly(isobutylene) (PIB) and poly(oxy)norbornenes.[23,24,25,26] Silicon wafers were

coated with thin films of a statistical copolymer bearing 1 - 70 mol% molecular

fractions of Hamilton receptor functionalities and Au-nanoparticles bearing multiple

complimentary barbituric acid recognition sites were fixed on these surfaces via

multiple hydrogen bonding processes (Fig. 12).

INTRODUCTION

10

Figure 12: Generalized concept of nanoparticle binding onto Hamilton receptor functionalized

copolymer surfaces.[26]

Since its development, the Hamilton receptor bonding motif has stirred considerable

interest in the research area of supramolecular chemistry and a plethora of

noncovalent systems based on this recognition principle can be found in the

literature.[27,28,29,30,31,32]

1.2. Noncovalent Supramolecular Porphyrin Assemblies

The high biological relevance and the remarkable photoelectronic properties of

porphyrins render them essential components in the design and synthesis of dynamic

supramolecular systems. Because of their remarkable high absorbance in the visible

region of the solar spectrum and their rich redox chemistry, porphyrins represent

INTRODUCTION

11

functional molecular units in important biological electron transport processes such

as photosynthesis and respiration. Therefore, the controlled organization of

porphyrins and other functional dye molecules and pigments like phthalocyanines

and perylenes via high dimensional self-assembly processes is expected to yield new

materials with unique photophysical and (opto)electronic properties.

1.2.1. Synthetic Systems Mimicking Photosynthesis

The absorption of sunlight and its conversion into usable chemical energy are

essential key processes in living, photosynthesis-dependent organisms. These

processes are realized by the absorption of photons through the chromophores of the

light harvesting complexes followed by the transport of the electrons to the reactive

center of the photosynthetic system. In the reactive center, charge separation

between donor and acceptor occurs and is further stabilized by a distant isolation of

the radical cation and anion as well as by subsequent ET steps along a “Down Hill”

cascade. Very interesting and well investigated examples of light harvesting antenna

complexes are the LH-1 and LH-2 complexes of purple bacteria.[33,34,35] Figure 13

shows the crystal structure of the peripheral light harvesting antenna complex LH-2

of the purple bacteria RS. MOLISCHIANUM.[36] The membrane spanning helices of the

α- and β-apoproteins form an αβ-octamer with a geometry comparable to the

geometry of a hollow cylinder. The inside part of the cylinder is consisted of

membrane spanning helices of the α-apoprotein (blue) while the helices of the β-

apoprotein (magenta) build up the outer shell. Furthermore, the circular wheel-like

arrangement of the α-helices of both apoproteins directs the bound

bacteriachlorophyll-a (green) and lycopene (yellow) molecules in a precise and

specific ring-shaped geometry realizing adequate intermolecular distances to

optimize electron coupling, photon caption and energy transfer.

INTRODUCTION

12

Figure 13: The LH-2 octameric complex from RS. MOLISCHIANUM.[36] (a) View from above with

N termini upward. The α-apoproteins (blue) and the α-apoproteins (magenta) are displayed as

Cα tracing tubes. The bacteriochlorophyll-a molecules (green) are represented bearing phytyl

substituents for easier differentation from the lycopenes (yellow). (b) Side view showing the α-

helical segments as cylinders and Mg atoms as white spheres.

The investigation of the structure and functionality in natural photosynthetic

assemblies has stimulated the development and examination of a variety of synthetic

light harvesting antenna systems based on multiple porphyrin arrays.[37] Figure 14

shows the oligomeric porphyrin assemblies 26 and 27 that were synthesized and

probed as light harvesting complex LH-2 mimics.[38] The complexes were built by the

self-assembly of six or five pairs of slipped cofacial porphyrin dimers via Zn-N donor-

acceptor interactions. The structural characteristics of 26 and 27 regarding the

circular wheel-like arrangement of the chromophores and the close Zn-to-Zn

distances are very similar emphasizing the resemblance to the natural LH-2 complex

as illustrated in Figure 13.

INTRODUCTION

13

Figure 14: Porphyrin assemblies 26 and 27 mimicking the light harvesting complex LH-2.[38]

Due to the remarkable inherent properties of fullerenes such as reversible, stepwise

addition of up to six electrons[39,40] and low reorganization energy accompanying

electron transfer,[41,42,43] a considerable variety of porphyrin donor-fullerene acceptor

linked dyads have been synthesized and intensively studied as promising light

energy harvesting systems.[44,45,46,47,48,49,50] Still, despite of the immense relevance of

hydrogen bonding based interactions in a variety of biological processes, only a

comparatively small number of hydrogen bonding stabilized self-assembled

porphyrin-fullerene conjugates can be found in the literature.[51,52,53,54,55] HIRSCH

published the self-assembly and the investigation of the photophysical properties of

supramolecular porphyrin-fullerene nanohybrids based on the Hamilton receptor

bonding motif.[56] The Hamilton receptor functionalized Sn- and Zn-porphyrins 29

were coordinated to C60 monoadducts 28 bearing cyanuric acid functionalities as

focal points and dendritic groups at the second malonate termini. Under visible light

irradiation, the supramolecular 28:29d complexes revealed a fast charge separation

generated by the photoexcited Zn-porphyrin chromophores. The ET transfer

processes within these systems were further examined and proved by time resolved

fluorescence and transient absorption measurements. Regarding the analogous

supramolecular Sn-porphyrin species 29a and 29c, instead of electron transfer only

energy transfer was observed which can be attributed to the different oxidation

potential of Sn-porphyrins.

INTRODUCTION

14

Figure 15: Schematic representation of selected 1:2 complexes between fullerene cyanurates

28 and Hamilton receptor functionalized porphyrins 29.[56]

INTRODUCTION

15

In this context, novel supramolecular architectures were self assembled around a Sn-

porphyrin bearing axial Hamilton receptor functionalities, as shown in Figure 16.

The Hamilton receptor functionalized porphyrin platform 30 was complexed with first

to third generation depsipeptide dendrons and dendrofullerene 31[57] bearing a

cyanuric acid functionality as a focal point.[58] The photophysical properties of the

supramolecular 30:312 aggregate were examined by fluorescence experiments and

also in this case, energy transfer instead of electron transfer occured.

Figure 16: Supramolecular 1:2 complex between Hamilton receptor functionalized Sn-porphyrin

30 and dendrofullerene 31.[58]

Furthermore, the realization of a variety of synthetic photocurrent generation devices

was achieved by taking advantage of the antenna effect through self-assembled

INTRODUCTION

16

monolayers (SAM) of porphyrins on appropriate electrode surfaces.[59,60,61,62] HIRSCH

and coworkers reported a synthetic photocurrent generation device consisting of an

ITO electrode, coated with a self-assembled monolayer stabilized by electrostatic

interactions between anionic dendro-fullerene 32, cationic porphyrin 33 (free base or

Zn-derivative), anionic Zn-porphyrin 34 and the cationic ferrocene 35.[63,64] On an ITO

electrode surface coated with PDDA polymer (for maximum density of positively

charged ammonium groups) a bilayer of 32 was firstly created and 33, 34, and 35

were then assembled (Figure 17). Upon irradiation with light, ferrocene 35 acted as

an electron donor, while the anionic Zn-porphyrin 34 functioned as a photosensitizer.

The cationic porphyrin 33 served as a photosensitizer as well as an energy acceptor

and fullerene derivative 32 was utilized as an electron acceptor. With increasing the

layer density, the IPCE was found to increase efficiently from 0.01 % up to 1.6 %

evolved by the final layer of ferrocene derivative 35. The assembly of 34 and 35

increased the absorption area in the solar light spectrum and within the excited states

of the self-assembled system energy was only transported to 32 and 33, respectively.

Upon the formation of the charge separated state 33+/32-, transport of electrons and

holes takes place in opposite directions thus, hampering charge recombination.

3335

34 32

Figure 17: Schematic representation of the noncovalent self-assembly of 32, 33, 34 and 35 on an ITO electrode.[63,64]

Recently, a new supramolecular self-assembled 1:2 complex consisting of a

Hamilton receptor functionalized perylene bisimide derivative and a C60 adduct

equipped with the barbituric acid functionality as a focal point was reported.[29]

Fluorescence quenching experiments revealed a strong fluorescence quenching of

INTRODUCTION

17

37 upon complexation with 36 and indicated an intermolecular charge transfer

process.

Figure 18: Supramolecular hydrogen-bonded self-assembly 38:372.[29]

Additionally, the photoelectrochemical properties of the supramolecular aggregate

were examined and for this purpose,

a layer of 37:362 was deposited on

the surface of an ITO electrode. A

steady cathodic photocurrent was

observed and a quick response of

the supramolecular system to the on-

and off-switching of the light source

was reported (Fig. 19).

Figure 19: Photocurrent generation of the supra- ar self-assembly layer of 36molecul and 37 under

irradiation with white light (20 mW/cm2).[29]

INTRODUCTION

18

1.2.2. Sensing of Chirality The great importance of chirality in Life and Nature is reflected in the restriction of the

existence of only one configuration of natural amino acids and in the high

enantioselectivity observed in enzyme catalyzed reactions. Since the discovery of the

molecular chirality by LOUIS PASTEUR in 1848, the synthesis and investigation of

chiral molecular and later on, supramolecular systems have become major targets in

organic chemistry. The characteristic and intensive electronic absorption of

Zn-porphyrins in the SORET band region (usually ε = 5 x 10-5 M-1cm-1) and the very

efficient excitonic coupling (up to 50 Å)[65] between two porphyrins render them very

appealing candidates for the highly sensitive detection of chirality. BEROVA published

a new microscale approach using the Zn-porphyrin tweezer 38 for the determination

of the absolute configuration of secondary alcohols and primary amines.[66,67] The

covalent attachment of the chiral substrates to the achiral tris-functional bidentate

carrier molecule (3-aminopropylamino)acetic acid and the complexation of the

conjugate 39 with 38 resulted in the formation of a 1:1 host-guest complex. In

general, two helical conformers are possible for the supramolecular sandwich

complexes which give rise to CD spectra with opposite COTTON effects. The favored

helical conformation depends on the sterical requirements at the stereogenic center

of the substrate therefore, enabling the determination of the absolute configuration.

INTRODUCTION

19

Figure 20: Schematic representation of the chiral sensing functionality of Zn-porphyrin tweezer

38.[67]

AIDA published the successful sensing of the helicity of peptides by using the cyclic

bis-Zn-porphyrin 40 as a host molecule.[68] The two Zn-porphyrins were connected

via two dynamic peptide helices of nonameric aminoisobutyric acid units and as a

result of the presence of equal amounts of L- and D-helices no CD effect of 41 was

observed. The ditopic coordination of the guest molecules led to intense CD effects

in the absorption area between 410 - 450 nm whose signs reflected the helical sense

of the coordinated peptides.

INTRODUCTION

20

Figure 21: Bis-porphyrin linked via dynamic peptide helices 40 and a chiral substrate 41.[68]

PROPOSAL

21

2. PROPOSAL The first target of the present work was the synthesis and characterization of a new

family of di- and tetra-substituted tetraphenylporphyrin derivatives equipped with the

Hamilton receptor recognition motif. The Hamilton receptor functionality should be

connected via rigid, inflexible linkages to the porphyrin core in order to provide

enhanced structural control over the corresponding supramolecular architectures.

The self-assembly of these Hamilton receptor porphyrins with guest molecules

equipped with a complimentary cyanuric/barbituric acid functionality was expected to

result in a variety of novel supramolecular host/guest complexes based upon multiple

hydrogen bonding with characteristics strongly depending on the nature of the guest

molecules. The properties of the resulting supramolecular architectures should be

probed by CD spectroscopy, 1H NMR-, fluorescence- and absorption-titration

experiments.

In a first step, the synthesis of a four-fold Hamilton receptor functionalized porphyrin

was proposed followed by the self-assembly with enantiomerically pure first to third

generation depsipeptide dendrons bearing complementary cyanuric acid

functionalities at their focal points. The resulting supramolecular, noncovalent

aggregates should be investigated by 1H NMR titration experiments and should be

further probed in terms of chirality transfer from the depsipeptide dendron guests to

the achiral Hamilton receptor functionalized porphyrin by means of CD spectroscopy.

Furthermore, the synthesis of bi-functionalized porphyrins with cis- and trans-

substitution pattern of the Hamilton receptor and a complementary trans-symmetric

porphyrin cyanurate was proposed. The cis- and trans-substitution patterns of the

Hamilton receptor bi-functionalized porphyrins in conjunction with the rigid structure

of the porphyrin core were expected to offer a well defined geometry of the host

moieties. Therefore, these molecular building blocks represent attractive molecular

units towards the construction of novel supramolecular architectures via self-

assembly processes with complimentary guests. For example, the combination of a

cis-symmetric Hamilton receptor functionalized porphyrin and a complementary

trans-symmetric porphyrin cyanurate is very likely to result in rectangular

architectures depending on the flexibility of the supramolecular complex.

The supramolecular host/guest complexes between the cis- and trans-symmetric

Hamilton receptor functionalized Zn-porphyrins and the first to third generation

PROPOSAL

22

depsipeptide dendrons, a second generation dendrofullerene and a cyanuric acid

substituted [60]fullerene derivative, as guest molecules, should be examined by 1H

NMR titration experiments and their photophysical properties should be investigated

by steady state fluorescence titration experiments and time resolved absorption

spectroscopy.

RESULTS AND DISCUSSION

23

3. RESULTS AND DISCUSSION

3.1. Synthesis of the Hamilton Receptor Derivatives The hydroxyl-substituted Hamilton receptor derivative 45[Error! Bookmark not defined.,69] was

synthesized as shown in scheme 1. The solubility of the deprotected Hamilton

receptor 45 was limited only to a few polar aprotic solvents such as THF, DMSO,

DMF and dioxane.

Scheme 1: Synthesis of the hydroxyl-substituted Hamilton receptor derivative 45.

The iodine-substituted Hamilton receptor 48 was synthesized as shown in scheme 2.

The diacid 46[70,71] was treated with SOCl2 at reflux and reacted with the amino

pyridine derivative 47[21] to afford the iodine-substituted Hamilton receptor 48 in 73 %

yield. The characterization of 48 by means of NMR spectroscopy in CDCl3 solvent

was possible but after approximately one hour, the samples precipitated and

remained insoluble in CHCl3 and CH2Cl2 at RT. Inter- and intramolecular aggregation

phenomena between the Hamilton receptor functionalities are considered to be the

reasons for this behavior.


24

Scheme 2: Synthesis of the iodine substituted Hamilton receptor 48.

3.2. Synthesis of the Porphyrin Precursors For the synthesis of a tetraphenylporphyrin with four cyanuric acid functionalities as

focal points the 6-(2,4,6-bioxo-triazinan-1-yl)hexyl 4-formylbenzoate 51 was chosen

as starting material and synthesized as shown in scheme 3.

1-(6-hydroxyhexyl)-[1,3,5]-triazin-2,4,6-trion 49[22,69] was reacted with the

commercially available 4-formyl benzoic acid 50 under DCC esterification conditions

and aldehyde 51 was obtained in 57 % yield.

Scheme 3: Synthesis of 6-(2,4,6-bioxo-triazinan-1-yl)hexyl 4-formylbenzoate 51.

An alternative synthetic pathway (Scheme 4) to the cyanuric acid substituted

benzaldehyde 54 turned out to be inappropriate. Three different reaction conditions

using the bromine derivative 52[69] and 4-hydroxybenzaldehyde 53 as starting

materials were investigated. In all displayed reaction conditions except (a), no [M]+

peak corresponding to the target molecule 54 was observed by FAB MS. The

solubility of the crude mixture obtained from reaction (a) was restricted only to

MeOH. Therefore, the purification by column chromatography on SiO2 was not

possible. Furthermore, recrystallization performed by slowly adding hexane or

pentane to a solution in MeOH was unsuccessful. Upon the addition of CH2Cl2,


25

precipitation occurred and the solid was filtrated, dried and analyzed by 1H NMR

spectroscopy. The 1H NMR spectrum revealed that only trace amounts of the target

molecule were present while the main percentage of the substance consisted of a

mixture of unidentified compounds. Therefore, the integration of the aromatic

resonances versus the integration of the CH2 protons was too low, pointing to the

presence of large quantities of oligomeric material.

Scheme 4: Alternative synthetic route of the cyanuric acid substituted benzaldehyde 54.

3.3. Synthesis and Characterization of the Porphyrin Derivatives

3.3.1. Synthesis of the Porphyrin Derivatives

The synthesis of the porphyrin derivatives 58 - 61 was achieved by reacting

4-tert-butylbenzaldehyde 57, methyl-4-formylbenzoate 55 and pyrrole 56 under

statistical LINDSEY[72] conditions (Scheme 5). The utilization of the para-tert-butyl

substituent was expected to assure good solubility of the porphyrin derivatives. TFA

was chosen as a catalyst for the condensation reaction and the different porphyrin

derivatives were isolated via repeated column chromatography using CH2Cl2/hexane

as an eluent. The more complicated substitution patterns of the porphyrins can be

also described using A and B as synonyms for the different substituents at the meso

positions of the porhyrinoid macrocycle (here A = 4-(tert-butyl)-phenyl and B =

4-methyl-formyl-phenyl). As can be expected from the difference in polaritiy, traces of

the tetrakis[4-(tert-butyl)-phenyl]porphyrin 58 eluted first, followed by the tris-[4-(tert-

butyl)-4-(methoxycarboxy)phenyl]porphyrin 59 and finally the trans- and cis-A2BB2

porphyrins 60 and 61. The AB3 and B4 porphyrin derivatives were not detected during


26

the separation procedure. In contradiction to the literature, TFA was used instead

of BF

[56]

3•OEt2 as a catalyst and 59 was isolated in an increased yield of 19 %.

Scheme 5: Synthesis of the cis- and trans-configured porphyrin isomers 60 and 61.

For the synthesis of the cis-configurated porphyrin derivative 65, 4-tert-butyl-

benzaldehyde 57 and 4-(trimethylsilylethynyl)benzaldehyde 62 were reacted under

statistical LINDSEY conditions as shown in scheme 6.

The reactivity of the two benzaldehydes was expected to be similar therefore, 57 and

62 were allowed to react in a 1:1 molar ratio using BF3•OEt2 as a catalyst. After

filtration of the crude reaction mixture over SiO2 and by using CH2Cl2 as eluent, the

separation of the different porphyrins was found to be difficult due to the similar

polarity of the peripheral [4-(tert-butyl)phenyl- and 4-(trimethylsilylethynyl)phenyl]-

substituents. Similar results have been reported in the literature when benzaldehyde

and 4-(trimethylsilylethynyl)benzaledhyde 62 were used for the synthesis of

tetraphenyl porphyrins.[73]


27

Scheme 6: Synthesis of the cis-configured porphyrin 65.

Several attempts to separate the silyl-protected porphyrins by column

chromatography (SiO2) using different mixtures of hexane/EtOAc (1st: 95/5, 2nd:

100/0→95/5) were unsuccessful. Those solvent mixtures were found to be promising

based on TLC but in the column chromatographic separation, extreme tailoring of the

porphyrin compounds made the isolation impossible. Attempts to separate the Zn-

porphyrins after metalation of the crude mixture with Zn2+ were also unsuccessfull.

Finally, the 4-(trimethylsilylethynyl)phenyl porphyrins were converted into the

corresponding deprotected 4-ethynylphenyl derivatives using a 1M solution of TBAF

in THF under inert conditions. The equivalents of TBAF were calculated assuming

the presence of four trimethylsilyl groups per porphyrin. Even after desilylation, the


28

separation of the ethynylphenyl porphyrins was found to be difficult. Separation was

achieved via repeated column chromatography using a mixture of CH2Cl2/hexane as

eluent. The tetrakis[4-(tert-butyl)-phenyl]porphyrin 58 eluted first (Rf = 0.49), followed

by the A3B porphyrin 63 (Rf = 0.43, A = 4-(tert-butyl)phenyl and B = 4-ethynylphenyl),

the cis-A2BB2 isomer 65 (Rf = 0.36) and the AB3 porphyrin 66 (Rf = 0.33). The

corresponding trans-A2B2B porphyrin isomer 64 was not detected. Free base

porphyrins experience NH-tautomerisation and therefore the α- and β-pyrrolic carbon

atoms can not be detected in the 13C NMR spectrum. In this case, differentiation

between 65, trans A2BB2-isomer 64 and 66 by H and C NMR analysis was not

feasible and thus, compounds 65 and 66 were converted into their corresponding Zn-

porphyrins 82 and 83. Regarding the very low yield of the targeted porphyrin 65, as

well as, the problematic separation and difficult TLC monitoring of the porphyrin

formation, replacement of the tert-butyl-substituent with a different solubilising group

was necessary. Several substituted benzaldehydes were subjected to condensation

reactions for the synthesis of A

1 13

3B porphyrins [B = 4-(trimethylsilyethynyl)phenyl

substituent] demonstrating that the utilization of ortho-methyl or ortho-methoxy

benzaldehydes provided better solubility and easier separation of the corresponding

porphyrin derivatives. Thus, mixed condensation reactions utilizing

2,4,6-trimethylbenzaldehyde and 3,5-dimethoxybenzaldehyde 67 were tested and

TLC monitoring showed the latter to be most appropriate. The utilization of

2,4,6-trimethylbenzaldehyde was found to be problematic due to the difficult

separation of the porphyrinoid cis- and trans-isomers.

[74]

The cis-configured porphyrin 71 was synthesized under statistical LINDSEY

conditions as shown in scheme 7. Based on the expected similar reactivity, the

aldehydes 62 and 67 were allowed to react in a 1:1 molar ratio using TFA as a

catalyst. The porphyrin isomers were separated from oligomeric materials by filtration

over SiO2 using a mixture of CH2Cl2/EtOAc 9:1 as eluent. The porphyrin compounds

were separated via repeated column chromatography (SiO2, hexane/EtOAc 8:2)

applying the solid state loading technique. Traces of the tetrakis[4-

(trimethylsilylethynyl)-phenyl porphyrin 68 eluted first, followed by the tris[4-

(trimethylsilylethynyl)]-4-[(3,5-dimethoxy)phenyl] porphyrin 69, the trans-isomer 70

and finally the cis-isomer 71.


29

Scheme 7: Synthesis of the cis-configured porphyrin 71.

The synthesis of the trans-isomeric porphyrin 75 (scheme 8) was achieved following

a [2+2] strategy by reacting aldehyde 62 and dipyrromethane 73[75] under LINDSEY

conditions.[72,66,67] The 2,4,6-Trimethoxy-phenyl substituent was chosen for the

synthesis of porphyrin 75 to avoid scrambling of the porphyrin substitution pattern

and provide a higher yield of the desired trans-isomer. The condensation reaction

was performed in CH2Cl2 using BF3•OEt2 as catalyst and DDQ as oxidant. The

porphyrin products were separated from oligomeric materials by filtration over SiO2

using CH2Cl2 as a solvent. The porphyrin-compounds were separated via repeated

column chromatography (SiO2) starting with CH2Cl2/cyclohexane 1/1 as eluent and

increasing the polarity of the solvent mixture to CH2Cl2/EtOAc 9/1. Traces of the

tetrakis[4-(trimethylsilylethynyl)-phenyl] porphyrin 68 eluted first followed by the


30

tris[4-(trimethylsilylethynyl)]4-[(2,4,6-methoxy)phenyl] porphyrin 74 and finally the

trans-A2BB2 porphyrin 75 (A = 4-(trimethylsilylethynyl)-phenyl and B =

2,4,6-trimethoxy-phenyl). The cis-A2B2B porphyrin isomer 76 was not detected. Finally,

the chromatographic separation of the trans- and cis-porphyrin isomers and the

purification of the corresponding target compound 75 were unsuccessful (see

chapter 3.4.2).

Scheme 8: Synthesis of the trans-configured porphyrin 75

Alternatively, dipyrromethane 77[78] was chosen as starting material for the synthesis

of the porphyrin 78. The stability of 77 to scrambling processes supresses the

formation of statistical side products. Furthermore, the tert-butyl substituent increases

the solubility and a decreased polarity of the corresponding porphyrin compounds

can be predicted. 77 was reacted in a 1:1 molar ratio with the commercially available

aldehyde 62 under LINDSEY conditions, using TFA as a catalyst and DDQ as an

oxidant. The only detectable side product 78b was formed by the minor impurity 77b

of the dipyrromethane. The target porphyrin 78 was separated from oligomeric


31

material by short filtration over SiO2 using CH2Cl2/EtOAc 95/5 as an eluent. After

repeated column chromatography (SiO2, CH2Cl2), 78 was obtained in 10 % yield.

Scheme 9: Synthesis of the trans-configured porphyrin 78.

3.3.2. Synthesis and Characterization of the Zinc Porphyrins

Porphyrins can coordinate a large variety of metals, semi-metals and even some

non-metals.[79] The ion size of the coordinated metal has a considerable influence on

the geometry of the metalo-porphyrin and the chemical properties.[80] Depending on

the size, metal ions can be either bound inside the central cavity of the porphyrin

macrocycle (in-plane) or side on (out-of-plane). Therefore, if the coordination number

of the inserted metal exceeds 4, additional ligands can be either bound cis (out-of-

plane) or trans axial (in-plane) to the coordinated metal. The insertion of Zn in metal

free porphyrins provides advantages like reversibility, increased stability, while the

photophysical properties of the Zn-porphyrin derivatives are comparable to Mg-

porphyrins[73] which is important for investigations by means of electronic transfer

(ET) studies. In this work, Zn-porphyrins have been prepared exclusively following

the acetate method.[81] A large excess of Zn(OAc)2 was stirred at RT or reflux with the

metal free porphyrin[74,81] in THF or CH2Cl2/MeOH and the reaction progress was


32

monitored by UV/Vis spectroscopy. Due to the fact that acetic acid is formed as a

minor side product, the Zn porphyrin derivatives should be stable under the reaction

conditions. The tetrakis[4-(trimethylsilylethynyl)-phenyl] porphyrin 68 was synthesized

according to the literature.[74]

Scheme 10: Generalized reaction scheme for the syntheses of the Zn-porphyrins 79-87.

The methyl esters of the Zn-porphyrins 79-81 were cleaved with a large excess of

KOH in THF at reflux.

Scheme 11: Generalized scheme for the syntheses of the porphyrins 88-90.


33

After the metal insertion, the 1H NMR and 13C NMR spectra of the Zn-porphyrins

compared to their metal free analogues do barely change. For example, the 1H NMR

spectra of the metal free porphyrin 71 and Zn-porphyrin 85 are shown in Figure 22.

Figure 22: 1H NMR spectrum (300 MHz, CDCl3, 25 °C): a) of the free base porphyrin 71; b) of the

Zn-porphyrin 85.

The spectra of the free base porphyrin 71 (Fig. 22a) and the Zn-porphyrin 85 (Fig.

22b) resembled each other with some minor differences. In Figure 22b, the

resonance signals of the pyrrolic NH protons are missing. Normally, these protons

experience a strong deshielding by the aromatic ring current and can be observed as

a broad singlet at around -3 ppm. Furthermore, the resolution of the splitting pattern


34

of the pyrrolic protons 8, 9, 20 and 22 is improved in spectrum (Fig. 22b). The

chemical shifts of the signals themselves remained unaffected.

It should be mentioned here, that the characterization of Zn-porphyrin 87 as well as

the derivatives 104 and 106 (p. 55 scheme 18 and p. 56 scheme 19) by 1H NMR

spectroscopy in CDCl3 led to unresolved and broad resonance signals (Fig. 23b).

However, the 1H NMR spectra of the free base porphyrin 78 showed the expected

resolution and splitting pattern. The low solubility of compound 87, can be excluded

as a possible reason since the solution prior and after the measurements was clear

and showed no traces of solid particles. Furthermore, less concentrated NMR sample

solutions of 87 in CDCl3 showed identical behavior.

Figure 23: 1H NMR spectra (400 MHz, 25 °C) of 87: using a) CDCl3/pyridine-d5, b) pure CDCl3.


35

Figure 23 shows the 1H NMR spectra of the Zn-porphyrin 87 in CDCl3 and CDCl3

containing one drop of pyridine-d5 in the region of -0.5 − 9 ppm. In Figure 23b, the

resonance signal of the TMS protons 21 at 0.4 ppm remained rather unaffected. On

the contrary, the spectrum displayed the resonance of the tert-butyl protons 1 as a

broad singlet at 1.4 ppm while, the resonance signals of the methyl protons 7 and

alkyl protons 6 were not observed. In the 7.5 − 9.0 ppm region, the resonances of the

aromatic protons appeared as broad and unresolved signals. After the addition of

one drop of deuterated pyridine to the solution of 87 in CDCl3, all the resonances

appeared as sharp and well resolved signals (Fig. 23a).

Figure 24: 13C NMR spectra (100.5 MHz, 25 °C) of 87: using a) CDCl3/pyridine-d5, b) pure CDCl3.


36

Interestingly, the same phenomenon was observed in the 13C NMR spectra of 87

(Fig. 24). The resonances of the alkyl- and methyl-carbons 7 and 6 were only visible

after the addition of one drop of pyridine-d5 (Fig. 24a). Even though, the two 13C

NMR spectra have been recorded with a different number of scans (Fig. 24a: 6450,

Fig. 24b: 5745) the intensity and resolution of the remaining resonances seems to be

still less pronounced (Figure 24b).

Figure 25: Temperature-dependent 1H NMR spectra (400 MHz, CDCl3) of 87.


37

The Zn-porphyrin 87 was also investigated by temperature-dependent 1H NMR

spectroscopy (Fig. 25) in the range of -40 − +50 °C in CDCl3. At very low

temperatures, all resonances appeared as broad and unresolved signals. In the

temperature range of the meassurements, the TMS resonance signal at 0.4 ppm

remained rather unaffected. Increasing the temperature to +50 °C the signals of the

aromatic protons 11, 12, 16 and 17 in the 7.8 - 8.7 ppm region became sharper but

the pyrrolic protons 12 at 8.5 ppm still remained unresolved. At 30 °C the resonance

of the phenylic protons 4 at 7.5 ppm became visible and the broad and unresolved

signal was slightly shifted to lower field with increasing the temperature. Regarding

the resonance signals of the alkyl protons 1, 6, 7 and 21 no clear tendency could be

found. In the range of -40 up to -20 °C the resonance signals of the alkyl protons 6

and methyl protons 7 are barely visible at 3.5 and 2.4 ppm, respectively. At higher

temperatures, the resonances broadened and were slightly shifted to higher field. In

the range of -10 °C to +20 °C these signals could not be differentiated from the

baseline. At +30 °C the resonances were visible again but remained unresolved even

at the temperature of +50 °C. At lower temperatures the resonances of the tert-butyl-

protons 1 could be observed as a broad signal at 1.4 ppm. With increasing the

temperature to +50 °C the resonance became sharp and was slightly shifted to lower

field.

Scheme 12: Synthesis of the Ni-porphyrin 91.

As the free base porphyrin 78 did not show similar behavior in the NMR experiments,

the coordination chemistry of the Zn2+ ion might possibly offer an explanation. Zn-

porphyrins are known to coordinate a variety of neutral ligands including N-, O-, S-,


38

P-donors and also charged ligands via the free fifth axial coordination site of the Zn2+

ion. Only a few examples of six-coordinated Zn-porphyrin complexes are known in

the literature[82,83,84]. As the Ni2+ ion is known to form predominantly square planar

four coordinated complexes,[80] the analogue 91 lacking available axial coordination

sites was synthesized according to the acetylacetonate method[85,86,87] and

characterized by means of NMR spectroscopy. As expected, the 1H- and 13C NMR-

spectra of 91 showed all resonances as sharp and well resolved signals (Fig. 26).

Figure 26: 1H NMR spectra (400 MHz, CDCl3, 25 °C) of 91.

According to PM3 calculations[88] (Fig. 27), the geometry optimized structure of 87 revealed that an intramolecular donor-acceptor bonding between the methoxy

oxygen and the free fifth axial coordination site of the Zn2+ ion is restricted due to the

4.9 Å distance between the O- and Zn-atoms. Furthermore, free rotation of the tert-

butyl-substituted phenyl rings is hindered because of the sterical repulsion between

the β-pyrrolic proton and the methoxy-substituent.[78] For this reason, the presence of

various rotational isomers in solution can be excluded.


39

Figure 27: PM3-caculated [88]

structure of Zn porphyrin 87.

Further semi-empirical PM3 calculations[89] performed on the Zn-porphyrin dimer

87:87 resulted in a 2.0 Å distance between the Zn2+ ion and the coordinated methoxy

oxygen (Figure 28). Therefore, the previously described spectroscopic phenomena

could originate from a considerably strong intermolecular interaction between the fifth

and/or sixth coordination site of the Zn2+ ion and the methoxy oxygen. This might

lead to the formation of high dimensional porphyrin aggregates.


40

Figure 28: PM3-calculated [89] structure of the Zn porphyrin dimer 87:87.

3.4. Synthesis and Characterization of the Zinc Porphyrins Bearing Hamilton Receptor or Cyanuric Acid Functionalities

3.4.1. Synthesis of a Four-fold Hamilton Receptor Functionalized Porphyrin via an Esterification Reaction

The four-fold Hamilton receptor porphyrin 93 was synthesized as shown in scheme

13. The esterification of the commercially available porphyrin tetraacid 92 with 45 under EDC coupling conditions led to the formation of the target molecule 93. The

reaction was performed in dry DMF using DMAP as a catalyst and the mixture was

left stirring at RT for 7 days.


41

Scheme 13: Synthesis of the four-fold Hamilton receptor functionalized porphyrin 93.

Due to the insolubility in most common organic solvents except DMF, THF and

DMSO and the high polarity of the target molecule, the purification of 93 was

achieved by repeated column chromatography with (SiO2, THF, THF/CH2Cl2 80:20)

followed by preparative HPLC (Nucleosil, THF/CH2Cl2 80:20). The use of DCC as

coupling reagent was disadvantageous because the removal of the DCU byproduct

turned out to be very difficult. Possibly, a strong complexation of the DCU with the

Hamilton receptor functionality via multiple hydrogen bonding might be responsible

for this behavior. Even after repeated GPC column chromatography (SX-3000, DMF)

the separation of the DCU was not successful. It should be noted here, that the

formation of all four possible porphyrin side products 94 - 97 (Fig. 29) was confirmed

by FAB-MS, when DCC or EDC were used as coupling reagents.


42

Figure 29: Byproducts 94 - 97 formed in the four-fold esterification reaction.

The assignment of the resonances in the 1H NMR and 13C NMR spectra of the

four-fold Hamilton receptor functionalized porphyrin 93 was carried out by executing

HETCOR- and COSY-NMR measurements in DMF. According to the D4h symmetry

of 93, the 1H NMR spectrum (Fig. 30) displayed the expected number of resonances

but unfortunately the resonance signals of the pyridinic protons 7 and 9 were

overlapping with the solvent residual signal at 8.1 ppm. In the upfield range between

0 - 3 ppm the spectrum revealed the characteristic coupling pattern of the alkyl chain

protons 1 - 3 which appeared as a well resolved multiplet and two triplets.The

resonance signals of the aromatic protons 19, 20 and 25 of the porphyrin unit were

located in the downfield region between 8.6 - 9.3 ppm. The pyridinic protons 8 resonated at 7.92 ppm as a dd while the ortho protons 15 of the isophthalic unit were

observed as a broad doublett at 8.5 ppm. In the range between 8.6 - 8.7 ppm the

spectra showed the two characteristic doublets corresponding to the aromatic

protons 19 and 20 of the meso-phenyl substituents followed by the singlet absorption

of the para protons 13 of the isophthalic unit. The β-pyrrolic protons 25 resonate as a

broad singlet at 9.1 ppm. In the region between 10.3 - 11.0 ppm the resonances of

the NH protons 5 and 11 were observed as broad singlets representing a


43

characteristic feature of Hamilton receptor derivatives. The pyrrolic NH protons 23

resonated at about –3 ppm and appeared as a broad singlet.

Figure 30: 1H NMR spectra (400 MHz, DMF-d7, 25 °C) of 93.

The resonance signals of the alkyl carbons 1, 2, and 3 were observed in the upfield

area of the 13C NMR spectrum of 93 (Fig. 31) In the 110 - 152 ppm range, the

spectrum showed the resonances of the aromatic carbons of the porphyrin-, pyridine-

and phenyl-units. The pyridinic carbons 7 and 9 resonated at 110.4 ppm, followed by

the resonances of the carbons 13, 8 and 14, respectively. In the area of 135 ppm the

spectrum showed the resonance signals of the phenylic carbons 19 and 20. The

intense resonances of the carbons 6, 10 and 15 appeared slightly more downfield

shifted in the 140 - 152 ppm region. At 163.1 and 165.7 ppm the spectrum displayed

the resonances of the carbonyl carbons 4 and 12, while the signal of the carbons 17

overlapped with the solvent residual peak at 162.7 ppm and was barely visible in the

spectrum. Free base porphyrins experience tautomerism of the pyrrolic NH protons

and therefore, the signals of the α- and β-carbons (here 24 and 25) were broad and

not distinguishable from the noise of the spectrum. Sometimes, the β-carbons 25 can

be observed as a very broad resonance signal at around 130 ppm.


44

Figure 31: 13C NMR spectra (100.5 MHz, DMF-d7, 25 °C) of 93.

Following the synthetic strategy for the tetrakis-Hamilton receptor porphyrin 93, the

synthesis of the acid functionalized porphyrins 88 - 90 (scheme 11 p. 32) was

pursued. However, the synthesis of compound 93 under these conditions has proved

to be very problematic due to the tedious purification steps and the very low yields of

the product.

Another synthetic approach to Hamilton receptor functionalized porphyrins using the

acid derivatives 88 - 90 is the amide formation between the amino-functionalized

Hamilton receptor derivative 48b and the Sn-porphyrin derivative 88b (Scheme 14).

The formation of amide bonds using EDC/DCC coupling conditions usually results in

good conversions and high yields. However, also this methodology was reported to

be rather unsatisfying for these porphyrin derivatives, as 29a was isolated in only

18 % yield.[56] Following this strategy for the synthesis of multiple Hamilton receptor

functionalized porphyrins, yields lower than 10 % can be expected and therefore, an

alternative C-C coupling chemistry was pursued.


45

Scheme 14: Synthesis of the Hamilton receptor functionalized Sn-porphyrin 29a.

3.4.2. Synthesis of the Trans- and Cis-configured Zinc Porphyrins Bearing Hamilton Receptor or Cyanuric Acid Functionalities

The SONOGASHIRA C-C coupling reaction has been successfully applied for the

synthesis of a diversity of covalently linked multi-porphyrin arrays.[90,91,92,93,94,95,96]

Therefore, the SONOGASHIRA C-C coupling reaction was chosen for the synthesis of

Hamilton receptor and cyanuric acid functionalized porphyrins.

The target molecule 99 was synthesized as shown in scheme 15. Desilylation of the

Zn-porphyrin 85 was achieved by using a 1 M solution of TBAF in THF. The

acetylenic coupling of the cis-isomeric porphyrin 98 with the Hamilton receptor

derivative 48 was performed using Pd2(dba)3 in combination with AsPh3 as catalysts.

To circumvent precipitation of the Hamilton receptor derivative, 48 was first allowed

to dissolve in THF followed by the addition of NEt3 and the other reagents. However,


46

TLC monitoring of the reaction was impossible and thus, the progress of the reaction

was monitored by FAB MS following the decrease of the intensity of the [M]+ peak of

48. After 24 h the FAB MS spectra of the reaction mixture revealed the peak

corresponding to the [M]+ of the target molecule 99 with low intensity. During the

progress of the reaction the intensity of the [M]+ peak corresponding to 99 changed

barely. Finally, after 6 d no [M]+ peak of 48 was detected and the Hamilton receptor

functionalized porphyrin 99 was purified via repeated column chromatography.

Scheme 15: Synthesis of the Hamilton receptor functionalized Zn-porphyrin 99.

Figure 32 shows the 1H NMR spectrum of the compound 99. In the 1.0 - 4.0 ppm

high field region, the spectrum displayed three sharp singlets which correspond to

the tert-butyl-, alkyl- and methyl protons 33, 31 and 1. The aromatic protons of the

porphyrin and the Hamilton receptor unit resonate in the down field region between

6.9 - 9.1 ppm. The resonance signals of the phenylic protons 4 and 3 were observed at 6.9 ppm and 7.4 ppm, respectively. The resonance of the aromatic protons 26


47

appeared as a dd while, the signals of the protons 13, 25 and 27 overlapped in the

area of 8 ppm. The resonance signals at 8.5 and 8.6 ppm were assigned as the para-

and ortho protons 21 and 19 of the isophthalic unit. The β-pyrrolic protons 8, 9, 35

and 37 resonated at around 9 ppm followed by two characteristic broad singlets of

the NH protons 23 and 29.

Figure 32: 1H NMR spectra (400 MHz, THF-d8, 25 °C) of 99.

The C2v symmetry of the Hamilton receptor porphyrin 99 is specifically confirmed by

the four resonance signals in the 131.8 - 132.6 ppm and in the 150.4 - 151.0 ppm

enlarged region of the 13C NMR spectrum (Fig. 33) which can be assigned to the β-

pyrrolic carbons 8, 9, 35 and 37 and the α-pyrrolic carbons 7, 10, 34 and 36. The

alkyl carbons 33, 32 and 31 resonated in the upfield region at 30.0, 31.6 and 50.7

ppm, respectively. The resonance signal of the methyl carbons 1 was observed at

55.6 ppm, followed by the two resonances of the acetylenic bridge carbons 16 and

17 at around 91 ppm. The phenylic carbon 3 resonated at 100.2 ppm, followed by the

resonances of the phenylic carbons 13, 14 and 4 at 110.2, 110.4 and 114.7 ppm,

respectively. The most downfield shifted resonances of the spectrum were assigned


48

as the phenylic carbon 2 at 159.9 ppm and the two carbonyl carbons 22 and 30 at

164.9 ppm and 170.8 ppm.

Figure 33: 13C NMR spectra (100.5 MHz, THF-d8, 25 °C) of 99.

For the synthesis of a Hamilton receptor or cyanuric acid substituted trans-configured

porphyrin two different porphyrins were synthesized and reacted under

SONOGASHIRA coupling conditions.

Desilylation of 86 was carried out by using a 1 M solution of TBAF in THF. The

deprotection proceeded quantitatively and after work up of the reaction, 100 was

used without further purification (purity verified by NMR analysis). The trans-isomeric

porphyrin 100 was coupled with the cyanuric acid derivative 101[97] under

SONOGASHIRA reaction conditions using Pd2(dba)3/AsPh3 as a catalyst and a

mixture of CH2Cl2/THF/NEt3 as a solvent (Scheme 16). The Pd2(dba)3/AsPh3 catalyst

has been proved to be very effective in the multiple acetylenic coupling involving

porphyrin derivatives.[90,95,96] To circumvent the precipitation of the cyanuric acid

derivative, 101 was first dissolved in pure THF followed by the addition of CH2Cl2,

NEt3 and the other reagents. In this case, monitoring of the progress of the reaction

by TLC and by FAB MS was impossible. The starting material 101 itself can not be


49

detected by FAB MS but after 12 h the FAB MS spectrum of the crude reaction

mixture revealed a low intensity [M]+ peak corresponding to the target compound

102. The reaction was allowed to proceed for 7 d under inert conditions and in the

dark, to guarantee completion of the coupling reaction. Purification by column

chromatography on SiO2 was proved to be difficult due to the low solubility and high

polarity of 102. Column chromatography on SiO2 was performed starting with EtOAc

as an eluent and increasing the polarity to THF/AcOH (9/1). The target compound

was detected in the THF/AcOH fractions (FAB MS). After high vacuum drying the

target fractions were completely insoluble in CH2Cl2, MeOH, EtOH, and acetonitrile

and showed very low solubility in solvents like EtOAc, CHCl3 and acetone. The best

solubility was achieved in DMSO followed by DMF and THF. In the two latter cases

the solution still remained cloudy. The high polarity and low solubility of 102 made its

further purification and characterization impossible.

Scheme 16: Synthesis of the cyanuric acid functionalized Zn-porphyrin 102.

The synthesic route to the trans-configured Hamilton receptor is displayed in scheme

17. The SONOGASHIRA coupling reaction was performed and monitored in the usual

manner as described for the synthesis of 99 (scheme 15, p. 46).


50


The characterization of the target compound 103 by NMR spectroscopy was proved

to be difficult. The 1H NMR spectra of 103 in CDCl3, THF-d8/CDCl3: 1/1, THF-d8,

DMF-d7 showed extreme broadening of the resonance signals which made further

assignment impossible.

However, the recorded 13C NMR spectrum (Figure 34) displayed better resolved

resonance signals. The upfield area of 20 - 55 ppm showed the resonance signals of

the alkyl chain carbon atoms 33, 34 and 35 followed by the two resonances of the

methyl carbons 1 and 5 at 56 ppm. The acetylenic carbons 17 and 18 resonated in

the area of 91 ppm, followed by the two resonance signals of the pyridine carbon

atoms 27 and 29 at 110.2 and 110.3 ppm, respectively. In the downfield region of

120 - 145 ppm the resonances attributed to the porphyrin- and Hamilton receptor-

carbons were overlapped rendering the accurate assignment impossible. In the area

of 130 ppm the resonances of the β-pyrrolic carbons 9 and 10 appeared as broad

and unresolved signals resembling the expected resolution pattern for free base

porphyrins. The use of AcOH as an eluent and the increasing concentration of AcOH

during the evaporation of the solvent might have resulted in partial or complete

demetalation of 103. However, this possibility can not be supported as this byproduct

was not detected by means of UV spectroscopy and by FAB MS. At 133 ppm the

spectra displayed the resonance signals of the aromatic carbons 14 and 15, followed


51

by the resonance signals of the α-pyrrolic carbons 8 and 11 at 150 ppm. The

resonance of the aromatic carbon 3 was observed at 162.0 ppm, followed by the two

most downfield shifted signals of the spectrum which can be attributed to the

carbonyl carbons 24 and 32 at 164.9 and 171.0 ppm.


The best resolved 1H NMR spectrum was recorded using DMSO as a solvent. In the

region of 1.0 - 4.5 ppm, the spectrum showed the resonance signals of the alkyl

chain protons 33 and 35 and the methyl protons 1 and 5. Theoretically, the tert-butyl

protons 35 and the alkyl protons 33 should appear as singlets but the spectrum

clearly showed two broad doublets at 1.0 and 2.3 ppm, respectively. The methyl

protons 1 and 5 displayed broad singlets at 3.5 and 4.1 ppm. The resonance signal

of the aromatic protons 3 was observed as a broad singlet at 6.7 ppm. In the 7 - 9

ppm region an accurate assignment was difficult due to overlapping of the aromatic

resonance signals of the Hamilton receptor and porphyrin protons. The resonances

of the NH protons 25 and 31 should normally be visible as two broad singlets but in

this case, two broad doublets were observed at 10.1 and 10.8 ppm.


52

Figure 35: 1H NMR spectra (400 MHz, DMSO-d6, 25 °C) of 103.

The unexpected splitting pattern of protons 33, 35, 25 and 31 and the extreme

broadening of the resonance signals in THF prompted us to further investigate the

purity of the starting materials and the target compound. The separation and

purification of the cis- and trans-isomers can be often problematic and sometimes

has even proved to be impossible by conventional methods.[76] The [2+2] strategy

under LINDSEY conditions using sterically demanding dipyrromethanes has been

applied to avoid scrambling of the porphyrinogen substitution pattern and therefore,

to supress the formation of the undesired cis-isomer. Using the dipyrromethane

method, formation of the latter is less favoured but generally, yields of 0.3 - 3 % can

be obtained. To rexamine the purity, starting compound 86 was subjected to HPLC

analysis using a Nucleosil column and CH2Cl2 as an eluent. The porphyrin 86 was

calculated to be 98.4 % pure (2.6 % of the cis-isomer impurity) by intergrating the

peaks corresponding to the main fraction and the impurity.

The Hamilton receptor functionalized Zn-porphyrin 103 was also subjected to HPLC

analysis on a diversity of stationary phases and solvent mixtures. Among these,


53

the application of a RP 18 column and THF/MeOH 6:4 as an eluent was found to be

the best but still, further purification of 103 remained impossible (Figure 36).

Figure 36: HPLC Elugram (RP 18, THF/MeOH 6:4) of 103.

The results obtained from HPLC confirmed the impurity of molecule 103 and

indicated the presence of more than two different Hamilton receptor functionalized

porphyrins (absorbing at 415 nm and 300 nm). Another fact which was in agreement

with the NMR spectroscopy is the existence of notable large percentages of one or

more Hamilton receptor side products as impurities (absorbing at 300 nm), in 103.

The analysis of the target molecule analogue side products observed during the

synthesis of 99 (scheme 15, p. 46) by means of 1 H NMR spectroscopy, pointed to a

possible complexation of these Hamilton receptor impurities via hydrogen bonding

within the recognition functionality of 103. The 13C NMR spectrum (Fig. 34) displayed

a smaller second resonance signal close to the resonance of the methyl carbons 35.

In the area of 160 - 167 ppm a few smaller resonance signals were observed which

were assigned as additional carbonyl carbons. The 1H NMR spectrum (Fig. 35)

showed splitted signals for the resonances corresponding to the Hamilton receptor

protons 35, 33, 31 and 25. Up to this point, no conclusion has been made on the

structure of the Hamilton receptor impurity. The starting material 48 was excluded as


54

an impurity because even traces would have been expected to be detectable in the

FAB MS spectra.

The experienced difficulties during the purification of the Hamilton receptor and

cyanuric acid functionalized trans-porphyrins 102 and 103 prompted us to design a

new porphyrin substructure with better solubilizing phenyl-substituents.

The cyanuric acid functionalized Hamilton receptor porphyrin 105 was synthesized

following the same synthetic methodology applied for target molecule 102 (Scheme

16, p. 49). The desilylation of porphyrin 87 using a 1M solution of TBAF in THF

resulted in the formation of 104 which was purified by column chromatography (SiO2,

CH2Cl2/EtOAc 97:3). 104 was coupled with the cyanuric acid derivative 101 under

SONOGASHIRA reaction conditions using Pd2(dba)3/AsPh3 as a catalyst. 101 was first

dissolved in THF, followed by the addition of the other reagents. In this case,

monitoring of the reaction progress was not possible by any conventional method.

Therefore, the reaction was allowed to proceed for 7 d under inert conditions and the

exclusion of light. A MALDI TOF mass spectrum of the crude reaction mixture

confirmed the formation of the target molecule 105. Column chromatography on SiO2

starting with pure CH2Cl2 as an eluent and increasing the polarity of the solvent to

CH2Cl2/MeOH 9:1 afforded two fractions containing minor amounts of 105. The

solubility of these two fractions was restricted to THF, DMSO, pyridine and DMF and

further purification was proved impossible. Column chromatography using THF as an

eluent and SiO2, Alox or SX-3000 as adsorbents was inappropriate. Furthermore,

recrystalization experiments using THF/acetone and THF/MeOH mixtures were

unsuccessful.


55

Scheme 18: Synthesis of the cyanuric acid functionalized Zn-porphyrin 105

The synthetic route for the trans-configured Hamilton receptor functionalized

porphyrin 106 diverges barely from the one applied for the synthesis of the target

compound 99 (Scheme 15, p. 46). After desylilation using TBAF in THF 104 was

reacted with the Hamilton receptor derivative 48 under SONOGASHIRA coupling

reaction conditions. Also in this case, the monitoring of the progress of the reaction

was only possible by FAB MS spectrometry and target compound 106 was purified

by repeated column chromatography on SiO2 in 31 % yield.


56


The 1H NMR spectrum of molecule 106 is displayed in Figure 37. The alkyl protons

36 and 34 of the Hamilton receptor unit resonated at 1.1 and 2.3 ppm, respectively.

The resonance signal of the tert-butyl protons 1 can be observed at 1.7 ppm followed

by the resonances of the methyl and alkyl protons 7 and 6 at 2.8 and 4.0 ppm. The

resonances of the aromatic protons of 106 were located in the down field region of

the spectrum between 7.8 - 8.9 ppm. The pyridinic protons 29 resonated at 7.8 ppm

as a dd while the resonances of 28 and 30 overlapped with the signal of the phenylic

protons 16 at 8.1 ppm. The most down field shifted resonances at 9.1 and 9.8 ppm

were attributed to the NH protons 26 and 32.


57

Figure 37: 1H NMR spectra (400 MHz, THF-d8, 25 °C) of 106.

The D2h symmetry is also reflected in the corresponding 13C NMR spectrum of 106.

The 30 - 75 ppm high field region of the spectrum displayed the resonances of the

alkyl carbons 1, 2, 6, 34 - 36 and the methyl carbons 7. The resonance signals of the

acetylenic bridge carbons 19 and 20 were observed at 89.5 and 92.0 ppm followed

by the resonances of the pyridinic carbons in the area of 110.3 ppm. Even after

analyzing the corresponding HETCOR and COSY spectra the explicit assignment of

all the signals in the 115 - 147 ppm spectral region was not feasible. In accordance

with the D2h symmetry, only two resonances for the α- and β-pyrrolic carbons 11, 12,

10 and 13 were observed at around 130 ppm and 153 ppm. The resonances of the

carbonyl carbons 25 and 33 experienced the strongest down field shift and are

located in the 165 - 172 ppm region of the spectrum.


58


3.4.3. Synthesis of a Four-fold Hamilton Receptor Functionalized Porphyrin via the SONOGASHIRA C-C Coupling Reaction

The cis- and trans-symmetric Hamilton receptor functionalized porphyrins 99 and 106

were obtained in satisfying yields by employing the SONOGASHIRA coupling reaction

conditions and therefore, it was challenging to test the applicability of these

conditions for the synthesis of a four-fold Hamilton receptor functionalized Zn-

porphyrin via multiple acetylenic coupling.

For the synthesis of a four-fold Hamilton receptor functionalized porphyrin, the

Zn-porphyrins 107 and 109 were reacted with the Hamilton receptor derivative 48

under SONOGASHIRA coupling reaction conditions using Pd2(dba)3 in combination

with AsPh3 as catalysts (Schemes 20 p. 60 and 21 p. 61). The free base porphyrin

68[74] was synthesized according to the literature. After metalation, the solubility of

Zn-porphyrin 84[98] was surprisingly low in CH2Cl2, CHCl3 and THF but

characterization by NMR spectroscopy was possible using a mixture of CS2/CDCl3 as

a solvent. Therefore, desylilation of 84 was performed in dry toluene using a 1 M


59

solution of TBAF in THF. Although the addition of TBAF to a solution of 84 was

reported to be performed at a temperature of -78 °C,[98] the desylation reaction was

carried out at room temperature. After 12 h reaction time, 1H NMR analysis confirmed

the incomplete conversion, and therefore, desylilation of 84 was repeated using THF

as a solvent. The Zn-porphyrin 107 was allowed to react with the Hamilton receptor

derivative 48 in the same manner as for target molecule 99 (scheme 15, p. 46).

After 6 d, the MALDI TOF spectra using different matrixes showed no [M]+ peak

corresponding to porphyrin derivative 108. However, the crude reaction mixture was

subjected to column chromatography on SiO2 applying the solid state loading

method. The solvent polarity was then slowly increased from pure CH2Cl2 up to

CH2Cl2/MeOH 96:4 and one fraction containing 108 (verified by MALDI TOF analysis)

was collected. This fraction was recrystallized using CH2Cl2/pentane and

characterized by 1H NMR spectroscopy. 1H NMR analysis pointed to the existence of

a large percentage of Hamilton receptor side products due to a notable amount of

resonances in the characteristic alkyl region of the spectrum. Subsequent column

chromatography on SiO2 using CH2Cl2/EtOAc and increasing the polarity of the

solvent stepwise to pure THF did not improve the purification of 108. Alternative

chromatographic methods were also tested but the isolation and purification of 108

was not successfull.


60

Scheme 20: Synthetic approach for the Hamilton receptor functionalized Zn-porphyrin 108.

Alternatively, we attempted the synthesis of a four-fold Hamilton receptor substituted

Zn-porphyrin via a different synthetic route as shown in scheme 21. The

Zn-porphyrin 109[99] was coupled with the Hamilton receptor derivative 48 under

SONOGASHIRA coupling conditions using Pd2(dba)3 in combination with AsPh3 as

catalyst. Firstly, 48 was dissolved in THF followed by the addition of the other

reagents. After 7 days, the crude reaction mixture was subjected to column

chromatography on SiO2 using pure CH2Cl2 as an eluent and gradually increasing the

polarity of the solvent to CH2Cl2/MeOH 9/1. The porphyrinoid fractions were analyzed

by FAB MS and MALDI TOF mass spectrometry but the molecular [M]+ peak of 110

was not observed.


61

Scheme 21: Synthetic approach for the Hamilton receptor functionalized Zn-porphyrin 110.

3.4.4. Synthesis of a Four-fold Cyanuric Acid Functionalized Porphyrin The synthesis of the cyanuric acid functionalized porphyrin 111 under LINDSEY[72]

conditions was not possible due to the poor solubility of 51 in common organic

solvents. The aldehyde 51 was neither soluble in CH2Cl2 nor in CHCl3 so the

condensation reaction was tested using non standard solvents and solvent mixtures

(Table 1). Usually, aldehyde 51 was allowed to react with pyrrole using either TFA or

BF3•OEt2 as a catalyst for 1 h at RT. After oxidation with DDQ, the reaction mixture

was stirred for 2 h at RT. The formation of porphyrinoid products was investigated by

means of UV/Vis spectroscopy. At the wavelength of λ = 420 nm (SORET band

region) no characteristic main absorption was observed therefore, excluding the

formation of the target molecule 111 and any porphyrinoid compounds.


62

[51] mol/l [56] mol/l catalyst [catalyst] mol/l solvent

1.0 x 10-2 1.0 x 10-2 TFA 1.0 x 10-2 THF

1.0 x 10-2 1.0 x 10-2 TFA 2.0 x 10-2 THF

1.0 x 10-2 1.0 x 10-2 TFA 1.0 x 10-2 THF/CH2Cl2 1/2

1.0 x 10-2 1.0 x 10-2 TFA 2.0 x 10-2 THF/CH2Cl2 1/2

1.0 x 10-2 1.0 x 10-2 TFA 1.0 x 10-2 CH3CN

1.0 x 10-2 1.0 x 10-2 TFA 2.0 x 10-2 CH3CN

1.0 x 10-2 1.0 x 10-2 BF3•OEt2 1.0 x 10-2 THF/CH2Cl2 1/2

1.0 x 10-2 1.0 x 10-2 BF3•OEt2 1.0 x 10-2 THF

1.0 x 10-2 1.0 x 10-2 BF3•OEt2 1.0 x 10-2 CH3CN

Table 1: Reaction conditions for the synthesis of 111.

Finally, the four-fold cyanuric acid substituted porphyrin 111 was synthesized via the

Adler-Longo method.[100] The aldehyde 51 was dissolved in propionic acid and

heated under reflux for 1 h. After the evaporation of the propionic acid the crude

reaction mixture was completely insoluble in most common solvents except THF.

Purification by column chromatography on SiO2 using different solvent mixtures of

THF as an eluent was not successfull. Also, Al2O3 as an adsorbent was found to be

unsuitable. Finally, the target molecule 111 was isolated in an overall yield of 3 % by

repeated GPC column chromatography using THF as an eluent.


63

Scheme 22: Synthesis of the four-fold cyanuric acid functionalized porphyrin 111.

Unfortunately, the assignment of the 1H NMR spectra of porphyrin 111 could not be

accomplished as most of the resonances of the alkyl-CH2 protons 3 - 8 overlapped

with the solvent residual- and the water-peaks. For this reason, only the more

characteristic 13C NMR spectrum will be discussed. As expected from the D4h

symmetry of 111, the 13C NMR spectrum (Fig. 39) displays 14 resonance signals.

The signals of the alkyl chain carbons 4 - 7 are observed in the 15 - 30 ppm area.

The carbons 3 of the CH2N group resonated at 41.0 ppm followed by the more

downfield shifted signal corresponding to carbon 8. In the region of 120 - 151 ppm,

the spectra displayed the resonance signals of the phenylic carbons 10 - 13 and the

porphyrin meso-carbons 14. Due to the tautomerisation of the pyrrolic NH protons,

the resonances of the α- and β-pyrrolic carbons 15 and 16 are much broadened and

can not be distinguished from the noise of the spectra.


64


3.5. Supramolecular Chiral Porphyrin Dendrimers Based on the Hamilton

Receptor Bonding Motif

The aggregation of the Hamilton receptor porphyrin 93 with the enantiomerically pure

depsipeptide dendrons 112 - 117, which were synthesized by HAGER,[101] should

result in the formation of novel, supramolecular architectures with unique properties.

The assembly of the supramolecular depsipeptide dendrimers 118 - 123 was

achieved by the four-fold complexation of 93 with the depsipetide cyanurates 112 - 117. Each depsipeptide cyanurate is bound to a complementary Hamilton receptor

unit via six hydrogen bonds. Effective binding of 93 with the dendrons 112 - 117 is

favored only in non-polar aprotic solvents such as CHCl3 and CH2Cl2.


65

Figure 40: Supramolecular porphyrin dendrimers 118 - 123.

However, 93 is insoluble in those solvents but it successively dissolves upon the

addition of 112 - 117 while forming the supramolecular complexes 118 - 123. The

stepwise solubilization can be followed by the deepening of the color of the solution

as shown in Figure 41.

The Hamilton receptor functionalized porphyrin 93 was suspended in 5 mL of

chloroform (HPLC-grade, freshly distilled over potassium carbonate to avoid

protonation of the free base porphyrin 93) followed by the stepwise addition of four

equivalents of the corresponding chiral depsipeptide dendrons 112 - 117. The

suspension of 93 in CHCl3 in the absence of any depsipeptide dendron remains

colorless. (a) After the addition of one equivalent of e.g. 112 the color of the solution

changed to red, (b) it deepened with increasing the concentration of the dendron

from slight reddish to intensively red. Even after the addition of three equivalents of


66

112 the solution remained still cloudy due to the presence of undissolved particles of

93 (d). Upon addition of four equivalents of the dendron 112 a clear deep red colored

solution was obtained and the whole material was dissolved (e).

Due to the insolubility of 93 in appropriate nonpolar aprotic solvents the

determination of the association constants by means of 1H NMR titration experiments

was impossible. For this reason, the formation of the supramolecular aggregates 118 - 123 was successfully demonstrated by UV/Vis-, CD- and NMR spectroscopies.

Figure 41: a) 93 suspended in 5 mL CHCl3; b) after addition of one, c) two, d) three and e) four

equivalents of 112, respectively.

Figure 42 shows the 1H NMR spectra of the porphyrin derivative 93, (a) the

depsipeptide dendron 112 (b) and its corresponding complex 118 (c) in the

diagnostic 4 - 11 ppm region. The alkyl chain protons 12 resonated as a multiplet at 4

ppm followed by five characteristic doublet signals of the benzyl protons 15 and 25.

The resonances of the protons 13 and 14, which are located at the chiral center of

112, displayed two doublets at 6 ppm. In the region between 7 - 8 ppm the spectrum

shows the resonances of the aromatic protons 16 - 24 and at 9 ppm, the signal of the

amide protons 11 appeared as a sharp singlet. After complexation with 93 the

characteristic resonances and splitting patterns of the dendrimer protons do barely

change, with the exception of the signals of 11 and 12. Compared to the free

dendron, the alkyl protons 12 in the complex 118 appeared as a broad and slightly

downfield shifted multiplet. In addition to the resonances of the dendritic protons 12 -

25 the 1H NMR spectrum of the complex 118 showed a set of new signals, attributed

to the Hamilton receptor functionalized porphyrin 93. In the downfield region the

resonances of the amide protons 1 and 5 were observed as broad singlets at 9.5 and


67

10.1 ppm. These chemical shifts are characteristic for a Hamilton receptor

functionality containing a hydrogen bonded cyanurate[101] and clearly prove the

successful self-assembly. The signal patterns and the chemical shifts of the aromatic

protons 2 - 10 within the complexes 118 - 123 are comparable to those of the free

receptor 93. In Figure 42 (c) and in all 1H NMR spectra of the compounds 118 - 123,

the signals of the amide protons 11 of the depsipeptide dendrons were missing and

this results from the dynamic character of the association of the complexes. As

shown from temperature dependent 1H NMR experiments on complexes of tritopic

Hamilton receptor derivative 7[22] with the chiral depsipeptide dendrons 112 - 117, the

temperature range between 0 - 50 °C represents a coalescence regime.[101] This

leads to very broad and thus, undetectable resonances of the amide protons 11 of

the bound and free depsipeptide cyanurates 112 - 117, at room temperature.

Typically for free base porphyrin derivatives, the pyrrolic NH protons of the

supramolecular complexes appeared at around –3 ppm as a broad singlet.


68

Figure 42: 1H NMR spectra (3.6 - 11.0 ppm region, 400 MHz, 25 °C). a) of Hamilton receptor substituted porphyrin 93 in DMF-d7; b) of depsipeptide dendrimer 112 in CDCl3 and c) its

corresponding complex 118 in CDCl3.


69

Complexation via hydrogen bonding in systems based on the Hamilton receptor

bonding motif leads to pronounced downfield shifts of the resonances of the Hamilton

receptor amide protons 1 and 5 [18,20,21,101] and as a consequence, NMR titration

experiments allow for the determination of the association constants. However, this is

only possible if all components are soluble in appropriate solvents such as CDCl3 or

CD2Cl2. Due to the insolubility of 93 in these solvents it was not possible to determine

the association constants and binding cooperativitities of the 1:4 complexes 118 -

123. On the other hand, NMR

titration studies successfully carried

out on 1:3 complexes of the

homotritopic Hamilton receptor 7

with the chiral depsipeptide

dendrons 112 - 117, using CDCl3 as

a solvent, can serve as an

appropriate model case for the

complexation of 93 with the same

dendrons.[101]

Figure 43: Tritopic Hamilton receptor derivative 7.[20]

The clearly separated electronic absorptions of the Hamilton receptor functionalized

porphyrins 93, 99 and 106 are well suited for the determination of chirality transfer,

caused by the complexation of the chiral depsipeptide dendrons 112 - 117, by means

of CD spectroscopy.

The UV/Vis spectrum of 93 (Fig. 44a and c) is characterized by the two most

intensive absorptions at λmax = 300 nm and λmax = 420 nm which are attributed to the

Hamilton receptor moieties and the SORET band of the porphyrin core, respectively.

The relative intensity and the width of these absorption bands, strongly depend on

the nature of the solvent. Due to pronounced intermolecular hydrogen bonding in

CHCl3, where 93 is almost insoluble, the SORET band is much broader and displays

a lower intensity than in THF (Fig. 44c). In THF, 93 is very soluble and no

intermolecular hydrogen bonding occurs. However, the corresponding λmax values are

independent of the solvent. The absorption spectra of the free dendrons 112 - 117


70

are only characterized by the transitions of the aromatic units at 270 nm (Fig. 44b).

The electronic absorption spectra of the complexes 118 - 123 represent a

superimposition of those of the constituting components (Fig. 44d). They are

dominated by the absorptions of the porphyrin receptor 93. In contrast to the

spectrum of the receptor 93 in chloroform, the SORET band is now the most

intensive. This is a consequence of the formation of the complexes 118 - 123, which

is accompanied by the de-aggregation of 93 and the breaking of the intermolecular

hydrogen bonds.

Figure 44: UV/Vis spectra of a) 93 suspended in CHCl3 (qualitative); b) 112 in CHCl3; c) 93 in

THF; d) complex 118 in CHCl3.

The CD-spectra of the dendrons 112 - 117 are shown in Figure 45a. Compounds

113, 115 and 117 display a positive COTTON effect in the area below 280 nm while

their corresponding enantiomers 112, 114 and 116 show a perfect mirror image

behavior in the same region.[101] The intensity of the CD-absorptions rises with the

increasing generation number of the depsipeptide dendrons.


71

Figure 45: CD spectra in CHCl3 a) of the chiral depsipeptide dendrons 112 - 117; b) of the

supramolecular porphyrin dendrimers 120-123.

For the chiroptical investigation of the complexes 118 - 123 one equivalent of the

porphyrin receptor 93 was mixed with four equivalents of the corresponding

depsipeptide-dendron 112 - 117 in HPLC grade chloroform. Due to the insolubility of

parent 93, all solutions were stirred overnight in order to guarantee quantitative

formation of the soluble complexes 118 - 123. The first generation complexes 118 and 119 showed no detectable COTTON effects in the characteristic region of the

Hamilton receptor and porphyrin absorptions. This is due to very weak chirality

transfer attributed to only two stereogenic centers per depsipeptide dendron 112 and

113. Even more importantly, the diastereoselective formation of a chiral super

structure can be excluded. However, the CD-spectra of the complexes 120 - 123 involving the second and third generation dendrons 114 - 117 revealed pronounced

chirality transfer. Two absorptions in the regions of the Hamilton receptor derivative

and the SORET band of the porphyrin at λmax = 302 and 420 nm respectively, were

observed (Fig. 45b and 46). Similarly to the absorption of the free dendrons (Fig.

45a) the CD spectra of 120 - 123 also display the COTTON effects of the chiral

depsipeptide-dendrons 114 - 117 at λmax = 260 nm. The CD spectra of the complexes

involving 114 and 116 display positive COTTON effects at 300 nm and negative

COTTON effects in the SORET band region at 420 nm. On the other hand, complexes

121 and 123 consisting of the corresponding enantiomeric dendrons of generation

two and three gave rise to CD spectra with opposite COTTON effects.


72

Figure 47: CD spectra of the Hamilton receptor porphyrin 93 in CHCl3 with a) 4 - 8 equiv. of the chiral depsipeptide dendrons 114 and 115; b) 4 - 8 equiv. of the chiral depsipeptide dendrons

116 and 117.

Significantly, the intensities of the CD absorptions in the regime of 93 at λmax = 302

and 420 nm do not correlate with the generation number. The corresponding

intensities of the second generation systems 120 and 121 are higher than those of

the third generation complexes 122 and 123 (Fig. 45b). This is especially true for the

absorption at λmax = 302 nm caused by the chirality transfer to the Hamilton receptor

functionality of 93. On the other hand the optical activity within the dendron region at

λmax = 260 nm remains unaffected and increases with the number of stereogenic

centers in the same way as for the free dendrons 112 - 117 (Fig. 45a). The

intensities of the CD absorptions at λmax = 302 and 420 nm do barely increase when

an excess of the second and third generation dendrons 114 - 117 is used for the

complexation with 93 (Fig. 46). A possible explanation for this behavior is the

different sterical requirement of the second and third generation dendrons 114, 115

and 116, 117, respectively. As demonstrated for the complexation of these dendrons

with the receptor 7 containing three instead of four binding sites, the association

constants and the positive cooperativity for a threefold complexation are much more

pronounced for the second generation dendrons 114, 115 than for the third

generation dendrons 116, 117. [101] This is due to the fact that the third generation

systems are too bulky to allow an effective binding of the third dendron. As a

consequence, only 50 % of the core 7 is involved in a 7:L3 complex (L = 116, 117) at

a stoichiometric 1:3 ratio of 7 and L. On the other hand, under the same conditions,


73

about 90 % of 7 are bound as 7:L3 complex when the second generation dendrons

114 and 115 are used. Although the benzene core of 7 is significantly smaller than

the porphyrin core of 93 the required four-fold binding may also cause overcrowding

when the third generation dendrons are allowed to react with 93 and the fraction of

3:L4 (L = 116, 117) within a 1:4 mixture of the components is considerably lower than

100 %. If on the other hand the four-fold binding shows a strong cooperativity, which

is very likely, the case for the complexation of the second generation dendrons 114 and 115, the 93:L4 species can be considered as predominant.

It can be assumed that the most stable conformation of such a 93:L4 complex has a

chiral propeller like shape with a left handed (Λ) or right handed (Δ) configuration

(Fig. 47). X-ray crystal structures of a series of meso-aryl substituted porphyrins

showed that in most cases the aryl rings are not oriented perpendicular to the

porphyrin plane but exhibit typical angles in the range between 65° and 80°.[102,103]

For this reason, the tetraphenylporphyrin moiety adopts chiral C4-symmetrical

conformations. This clearly demonstrates that such propeller like conformations are

preferred which is also confirmed by theoretical calculations (Fig. 47).

Figure 47: PM3-calculated model of the C4-symmetrical propeller-shaped tetraphenlyporphyrin

with Δ and Λ configuration.[88]

As the enantiomerically pure dendrons 114 and 115 with all-R and all-S configuration

respectively, were utilized, the formation of two diastereoisomers such as Λ-93: all-R-

1144 and Δ-93: all-R-1154 is expected. One of these diastereomers has a lower

energy than the other and will be formed preferentially. The presence of an excess of

one diastereoisomer involving a chiral supramolecular motif will cause an increased

intensity of the CD absorptions which is indeed observed for the complexes 120 and


74

121 compared to the third generation analoges 122 and 123. Obviously, this

phenomenon is much less pronounced for the complexation of the third generation

dendrons because the formation of the corresponding 93:L4 complexes is less

favoured and the diastereoselective formation of distinct chiral superstructures is less

preferred. Concerning the complexation of the second generation dendrons 114 and

15 the scenario pointed to a case of supramolecular chirogenesis and has a variety

of precedents in literature. Examples are chirality induction in the achiral bis (zinc

octaethylporphyrin) (ZnD) by complexation of enantiomerically pure amino acids and

other chiral amines and alcohols.[104,105,106,107,108] Related behavior was also observed

with a free base porphyrin, covalently bound to eight peripheral Zn-porphyrins via

enantiomerically pure nucleoside linkers[109] and a self-assembled system constituted

of Zn-porphyrin-appended foldamers and a chiral C60 adduct incorporating histidine

moieties.[110] In the former case the optical activity of the nona-porphyrin system was

interpreted by the diastereoselective preference of a helical tetraphenylporphyrin

conformation. A COTTON effect was observed in the SORET band region which

resembles those of the complexes 120 - 123 (Fig. 45b) but is much more

pronounced. The COTTON effect of the reported supramolecular structure [107,108] was

found to be much less pronounced in the SORET band region than that of 120 - 123.

Also in this case, the preference of a specific helical conformation of the entire

supramolecular construct involving phenylporphyrine building blocks was suggested.

Generally, the Hamilton receptor functionalized Zn-porphyrins 99 and 106 showed

good solubility in non-polar aprotic solvents (e.g. CHCl3, CH2Cl2) and were subjected

to 1H NMR titration analysis with the chiral depsipeptide dendrons 113, 115 and 116.

The corresponding supramolecular complexes were also tested for chirality transfer

but in opposition to the supramolecular aggregates involving porphyrin 93, the CD

meassurements revealed no CD effects in the characteristic absorption regions of the

Hamilton receptor functionalized Zn-porphyrins 99 and 106.


75

Figure 48: Cis- and trans-symmetric supramolecular Zn-porphyrin dendrimer aggregates of 99

and 106.

The association constants and the cooperativity phenomena of the 1:2

supramolecular complexes consisting of 99:L2 and 106:L2 (L = 113, 115, and 116)

were determined by 1H NMR titration experiments,[111] in CDCl3 solvent. These

experiments were performed by the stepwise addition of 40 µl of a 2.5 mM solution of

113, 115 and 116 respectively, to 0.5 mL of a 0.5 mM solution of 99 or 106 in CDCl3.

It has been reported before that Hamilton receptor substituted molecules tend to form

rather stable intermolecular aggregates via multiple hydrogen bonding in non-polar,

non-coordinating solvents like CDCl3.[56,58,101] This phenomenon leads to rather broad

and unresolved peaks in the 1H NMR spectra of the free Hamilton receptor derivative

(Fig. 50). The successive complexation of the corresponding cyanurate guest with

the Hamilton receptor host leads to the breakage of the intermolecular aggregates

accompanied by a noticeable sharpening of the resonance signals. Equally, the NH1

and the NH2 resonances of the Hamilton receptor functionality undergo a continuous

downfield shift until the 1:2 complexes prevail above the other aggregates in solution.

After the addition of 0.4 equivalents of 113 the NH3 protons of the cyanuric moiety

were observed at 13.4 ppm. In contrast to the amide protons of the Hamilton receptor

functionality, the resonance of the NH3 protons experienced a high field shift and

increased broadening due to fast exchange processes between free and bound

cyanurate. Furthermore, this average signal disappeared after the addition of 2.4

equivalents of the guest molecule. The supramolecular hydrogen bonded assemblies

undergo continuous self-assembly and dis-assembly processes[20] and the dynamic

character of these systems is revealed by temperature dependent 1H NMR


76

spectroscopy. Figure 49 shows the coordination motif and the 1H NMR spectra of a

1:8 mixture of 99 and 113 at various temperatures.

Figure 49: 1H NMR spectra (400 MHz, CDCl3) of a 1:8 mixture of 99 and 113 at various temperatures.

Below 0 °C, the NH1 and NH2 of the Hamilton receptor were observed as broad and

unresolved signals. With increasing the temperature to 20 °C these resonances

sharpen. In the temperature range of -40 - 20 °C two resonance signals related to the

free and bound NH3 protons of the cyanuric moiety were visible indicating a slow

association-disassociation equilibrium on the NMR time scale. Above 0 °C the NH3


77

resonance of the cyanuric moiety is observed as a very broad signal and cannot be

detected anymore. Temperature dependent 1H NMR spectroscopy analyzing similar

supramolecular complexes in the range of -60 − 90 °C using deuterated

dichloroethane as a solvent verified that the temperature interval of 0 − 50 °C

represents a coalescence regime.[101]

Figure 50. Chemical shifts of the NH1, NH2 and NH3 protons during the titration of 99 with the guest molecule 113 (1H NMR spectra, 400 MHz, CDCl3, 25 °C). After the addition of: a) 0 equiv. 113; b) 0.4 equiv. 113; c) 0.8 equiv. 113; d) 1.2 equiv. 113; e) 1.6 equiv. 113; f ) 2.0 equiv. 113;

and g) 2.4 equiv. 113.

Figure 50 displays the chemical shifts of the NH1 and NH2 protons of the Hamilton

receptor substituted porphyrin 99 as a function of the added first generation dendron


78

113. The equilibrium between the free and bound cyanurate is fast on the NMR time

scale (coalescence regime). The breakage of the intermolecular hydrogen bonds of

99 and 106 requires some time and to guarantee establishment of stable equilibria,

the 1H NMR spectra of each titration step were recorded earliest after 45 min. of each

addition.

The NMR titration plots for the first generation supramolecular complexes 99:1132 (Figures 51) and 106:1132 (Figures 52, p. 80) display a sigmoidal shape with an

inflection point at around 0.6 equivalents thus, reflecting positive pronounced

cooperativity.[112,113,114] This effect weakens in both titration series (Figures 51 and

52) with increasing the generation number. The NMR titration plots for the first

generation dendron 113 revealed the most pronounced downfield shifts pointing to

more effective complexation which is also reflected in the higher association

constants (Table 2, p. 81).

Figures 51. NMR titration plots of the chemical shifts of the NH1 and NH2 of 99 as a function of the added equivalents of 113, 115 and 116, respectively.


79

The calculation of the association constants (Table 2, p. 81) and further work up of

the NMR titration raw data was performed using the Chem-Equi program. [115,116]

These calculations were based on the assumption of two equilibriums (Equations 1 - 2) between the Zn-porphyrins 99 and 106 (C) and the depsipeptide dendrons 113,

115 and 116 (L).

(1) K1: C + L

K2: L + CL

CL

CL2 (2)

In the case of identical and independent binding sites the multiple binding takes place

under statistical conditions and Equation (3) becomes relevant (t = total number of

binding sites, t = 2).

1)n1)(t(nn)n(t

KK

n

1n

+−+−

=+ (3)

If positive cooperativity becomes relevant, the binding strength of the (n+1)th ligand is

enhanced leading to a higher Kn+1/Kn value compared with the expected value

realized by statistical binding and thus, the equation becomes unequal (3).[112] Finally,

the experimental Kn+1/Kn values were found to be much higher than the theoretical

ones estimated by Equation (3). This clearly demonstrates positive pronounced

cooperativity for the supramolecular C:L2 complexes.


80

Figures 52. NMR titration plots of the chemical shifts of the NH1 and NH2 of 106 as a function of

the added equivalents of 113, 115 and 116, respectively.

As expected due to sterical reasons, the association constants for the

supramolecular self-assemblies 106:L2 were found to be higher than the K values for

the counterpart systems 99:L2 (L = 113, 115 and 116). The large difference between

the K1 and K2 is reflecting the pronounced positive cooperativity for these systems.

This tendency was found to be inversely proportional to the generation number of the

ligands. In general, the association constants for the second binding step decline with

increasing the generation number of the depsipeptide dendrons 113, 115 and 116.

However, the K1 values obtained for the second generation dendrons ligands 115

prevail over the values of the self-assemblies with the first generation dendrons 113.

A possible explanation for this behavior could be based on the different spatial

arrangement of the ligands. An open chain Hamilton receptor like 99 or 106 is able to

adopt three different conformations depending on the degree of intermolecular

aggregation and complexation. A photophysical study based on different generation


81

poly(propyleneamine) dendrimers with Hamilton receptors moieties as focal points

revealed that the binding of a guest molecule forces the Hamilton recognition site into

the in plane cis-cis configuration which is necessary for an effective complexation.[20]

Equally, the binding of a dendritic ligand weakens the intermolecular aggregation by

the formation of a better soluble C:L1 intermediate providing a better accessible free

binding site and alleviating the second complexation step. This effect was found to be

much more pronounced with increasing the generation number and sterical loading

of the guest molecules. On the other hand, the periphery of the more bulky third

generation dendron 116 introduces additional sterical hindrance resulting in the

lowest K1 values. These results are in good agreement with earlier studies

demonstrating the necessity of a favorable balance between solubility and sterical

demands.

log K1

[Lmol-1]

Log K2

[Lmol-1]

R [%]

rmax

nH

99:113 3.42 8.14 0.48 0.88 0.79

99:115 4.02 7.80 0.30 0.53 0.35

99:116 3.80 7.27 0.46 0.41 0.26

106:113 4.31 8.97 0.38 0.86 0.75

106:115 4.67 8.78 0.56 0.60 0.43

106:116 4.14 8.11 0.45 0.61 0.44

Table 2. Association constants, R factor, rmax and Hill coefficients (nH) for the 1:2 complexes of

99 and 106 with dendrons 113, 115 and 116.

The self-assembly processes feature a dynamic character (see also Fig. 49, p. 76)

and as a consequence, three different species can be present in solution. However,

the successful formation of the respective 1:2 complexes is reflected in the graphical

interpretation of all the possible C:Ln complexes present in solution (C = 99 or 106,

n = 0 - 2, L = 113, 115 and 116) as a function of the concentration of the

corresponding ligands L (Figures 53 and 54, p. 82 and p. 83). In general, at already

low concentrations of 113, 115 and 116 the C:L2 complexes prevail over the C:L1

species and after the addition of two equivalents the amount of the self-assemblies

with 1:2 stoichiometry ranges between 45 - 90 %. Due to the increased sterical

demand, the formation of the C:L2 self-assemblies with the bulkier third generation


82

dendron 116 are much less pronounced and the complexes with 1:1 stoichiometry

prevail until 1.6 or more equivalents of the dendron are added. The cis-configuration

of porphyrin 99 leads to an increased sterical loading of the Hamilton receptor

binding sites. Therefore, the formation of the C:L2 complexes is less pronounced and

this is reflected in the gradient of the curves. After the addition of two equivalents of

the bulky third generation dendron 116, the concentration of the 106: 1162 complexes

reaches already 70 % while, the concentration of the 99:1162 assemblies is only

45 %.

Figures 53: Distribution in percent of 99 as a free core and within the complexes 99:Ln (n = 1 -

2, L = 113, 115 and 116) as a function of the added equivalents of dendrons 113, 115 and 116. These data were obtained via analysis of the NMR titration plots using the computer program

Chem-Equi.[115-116]


83

Figures 54: Distribution in percent of 106 as a free core and within the complexes 106:Ln (n = 1 - 2, L = 113, 115 and 116) as a function of the added equivalents of dendrons 113, 115 and

116. These data were obtained via analysis of the NMR titration plots using the computer program Chem-Equi.[115-116]

The pronounced positive cooperativity of the association processes is also reflected

in the shape of the SCATCHARD[117] plots for the C:L2 systems (C = 99 or 106, L =

113, 115 and 116).

For the graphical interpretation of the SCATCHARD Equation (5) the determination of

the occupancy r (Equation 4) describing the average number of bound ligands is

necessary.

[ ] [ ][ ] [ ] [ ]2

2

CLCLCCL2CLr++

+= (4)


84

In the case of statistical binding the binding polynomial can be equalized with (1+Qx)t

and r becomes equal to tQx(1+Qx)t-1 with x referring to the concentration of L.

Finally, r can be described by the SCATCHARD Equation (5).

)1( QxtQxr+

= (5)

The SCATCHARD plots (Fig. 55 and 56) exhibit convex shaped curves demonstrating

a characteristic feature of pronounced positive cooperativity. In the case of a

statistical binding the shape would be a straight line and pronounced negative

cooperativity would even result in concave shaped SCATCHARD plots.[112] The

dimension of cooperativity is also reflected in the values of the Hill constants nH[118,119]

determined from the maxima of the SCATCHARD plots rmax (Equation 6).

max

max

rtrnH

−= (6)

The formation of the C:L2 complexes with the first generation dendron ligand 113

were found to be accompanied by the largest pronounced positive cooperativity

effects reflected in the largest nH values (Table 2, p. 81) among the other

aggregates. Finally, the nH values decline with increasing the generation number and

the sterical loading of the dendrons which is also illustrated in the shape of the

SCATCHARD plots. With increasing the generation number of the ligands the curves

tend to become more and more flat but still maintaining a convex shaped form.


85

Figures 55: SCATCHARD Plots for the systems 99:L2 (L = 113, 115 and 116).

Figures 56: SCATCHARD Plots for the systems 106:L2 (L = 113, 115 and 116).


86

Finally, Job’s Plot analysis was performed with the 1H NMR data (Figures 57) for the

C:L2 complexes (i.e. C = 99 and L = 115, C = 106 and L = 113). Overall, the obtained

Job’s plots give rise to maxima at a mole fraction of 0.33. This indeed confirms the

underlying stoichiometry.

Figures 57: Job’s plot analysis of the 1H NMR titration of a) 99 with 115 and b) 106 with 113 in

CDCl3.

3.6. Synthesis and Photophysical Properties of Novel Supramolecular Porphyrin-Fullerene Dendrimers

The photophysical and (opto)electronic properties of metalloporphyrins are truly

unique,[80,120] especially when they are combined with fullerenes. What renders

fullerenes exceptional is their capability to accept reversibly up to six electrons[39,40]

while exhibiting a low reorganization energy that is associated with each of these

electron transfer steps.[41,42,43] However, to take in consideration the considerable

number of electron donor acceptor conjugates based on the combination of

porphyrins and fullerenes, [44,45,46,47,48,49,50] hydrogen bonding is still a hardly ever

employed motif to integrate the functional building blocks (i. e. porphyrins and

fullerenes) into fully operating reaction center models.[51,52,53,54,55]

Therefore, supramolecular 1:2 stoichiometric aggregates consisting of the Zn-

porphyrins 99 or 106 and the complimentary fullerene cyanurates 124[57] or 125[121]


87

were subjected to a series of photophysical investigations (Fig. 59, 61 - 64) carried

out in collaboration with Bruno Grimm (Dirk Guldi group).

Figure 58: Depsipeptide fullerene derivatives 124[57] (all S configuration) and cyanuric acid

substituted fullerene derivative 125.[121]

To this end, Zn-porphyrin 99 solutions (i.e., dichloromethane, or ortho-

dichlorobenzene) were titrated with variable concentrations of the fullerene derivative

124. We note – in perfect agreement with previous investigation – that adding 124 to

solutions of 99 evoked a gradual red-shift of the absorption features. For example,

the SORET-band shifted as much as 3 nm. Moreover, when substracting the fullerene

absorption, a net decrease in the intensity of the SORET- and Q-bands evolved

(Fig. 59). The presence of isosbestic points (i.e., 418 and 428 nm) implies effective

ground state interactions between the Zn-porphyrin and C60.[122,123,124,125] A newly

developing absorption band at 780 nm further corroborates this assumption.

With the changes in the absorption features in hand we quantified the binding

constants. Considering the data at 423 nm, where the absorption diminishes as a

function of concentration of 124, log K values of 3.30 L mol-1 and 6.71 L mol-1 for the

first and second binding process, were calculated.[126] Notable is the excellent

agreement with the values that were calculated based on the NMR titrations.

Decisive information about the stoichiometry was obtained by Job’s plot titration

experiments, where a maximum at 0.33 points to a 1:2 stoichiometry of the host-

guest complex 99:124. (Fig. 60)


88

Figure 59: Changes in the Zn-porphyrin electronic absorption spectra of 99 (9.0 x 10-7 M) in

CH2Cl2 upon successive addition of 124 (0 – 2.0 x 10-5 M).

In contrast, titrations involving Zn-porphyrin 106 and fullerene 124 in

ortho-dichlorobenzene/pyridine (1000:1) revealed only a slight decrease of the

SORET-band and a lack of appreciable shift. A reasonable assumption infers – in

addition to axial coordination – weaker binding in the presence of pyridine. Still,

isosbestic points at 430 and

440 nm provided evidence

for mutually interacting Zn-

porphyrin 106 and C60. A

similar conclusion is derived

for Zn-porphyrin 99 and

fullerene derivative 125[121]

in a mixture of

chloroform/carbon disulfide

(5:1). Figure 60: Job’s plot analysis of the absorption titration

of 99 with 124 in CH2Cl2.


89

However, implementation of p-phenylethynylene spacers hampers sizeable ground

state interactions.[127,128]

Decisive confirmation of electron donor acceptor interactions came from

complementary steady-state fluorescence experiments. Here, the characteristic

fluorescence of Zn-porphyrin 99 (φF = 0.04) was used and monitored while adding

variable amounts of the fullerene derivative 124. As shown in Figure 61, the

Zn-porphyrin fluorescence was subjected to a strong quenching once 124 was

present. Tentatively, we implicate for this new deactivation pathway an electron

transfer evolving from the photoexcited Zn-porphyrin. Spectroscopic evidence in

favor of the electron transfer hypothesis came from transient absoprption

measurements-vide infra.

The gradual quenching was used to estimate the binding constants (Fig. 61). Using

the sigmoidal dependency between IF/I0 and C60 derivative concentration led via

Equation (7) to log K1 = 3.37 L mol-1 and log K2 = 7.30 L mol-1.

(7) )cβcK(1

)cβIcKbc(II 2D1201

2D12D100

F ⋅+⋅+⋅⋅+⋅⋅⋅+

= ∞

In Equation (7), I0 and I∞ refer to the initial and the final fluorescence intensity,

respectively, while c0 is the total porphyrin concentration. The added fullerene

derivative concentration is given by cD. K1 is the first binding constant and β12 equals

to K1*K2.[129] The perfect agreement with the NMR and absorption assays

strengthens our hypothesis for positive cooperativity.

An important test experiment was focused on the non photoactive dendron 115 which

was added in variable amounts to a mixture of 99 and 124 in ortho-dichlorbenzene.

Upon increasing the concentration of 115 a ligand exchange reaction replaces 124

and the initial fluorescence of 99 is quantitatively restored.


90

Figure 61. a) Changes in the steady-state fluorescence of Zn-porphyrin 99 (8 x 10-7 M) upon

successive addition of 124 (0 M – 1.02 x 10-5 M) in ODCB, λexc = 424 nm. b) Fluorescence

intensity at 600 nm of 99 and 99 / 124 with non-linear fit according to equation (7).

The Zn-porphyrin fluorescence enabled as well determination of the electronic

communication between Zn-porphyrin 106 and 124 – log K1 = 3.92 L mol-1 and log K2

= 5.80 L mol-1. Interestingly, the difference between these two binding constants is

much less when compared with the difference observed for 99:124. A weaker

cooperativity might arise from the trans positioning of the two Hamilton receptors.

In the next step, the fluorescence quantum yields at the plateau values –

corresponding to a quantitative conversion – were taken to gather first information

about the excited state deactivation dynamics. In 99:124, for example, an electron-

transfer (7.6 x 109 s-1) outperforms the intrinsic decay of the singlet excited state of

99, namely intersystem crossing (4.7 x 108 s-1).

Complex log K1

[Lmol-1]

log K2

[Lmol-1]

fluorescence

lifetime (τ)

99/124 (ns)

Solvent

99:124 3.54 6.37 1.6/0.5 dichloromethane

99:124 3.37 7.30 1.8/0.3 ortho-dichlorobenzene

106:124 3.92 5.80 ortho-dichlorobenzene /

pyridine 1000:1

Table 3. Association constants obtained via fluorescence titration for the 1:2 complexes of 99

and 106 with fullerene derivative 124 and fluorescence lifetimes of 99/124.


91

Once the steady-state characterization – absorption and fluorescence – was

completed, we turned to time-resolved fluorescence measurements. The

fluorescence of Zn-porphyrin 99 was best fitted by a mono-exponential decay

function with a lifetime that typically ranged from 1.5 to 1.8 ns when dichloromethane

and ortho-dichlorobenzene were used as solvents. In the presence of 124, a

reasonable fit of the fluorescence decay was only achieved when a bi-exponential

fitting function was used. In particular, a long lifetime of ca. 1.5 ns – corresponding to

free, uncomplexed 99 – and a short lifetime of 0.4 ns – corresponding to complexed

99:124 – emerged. The pre-exponential factor of the long and the short lifetimes

decreased and increased with increasing concentration of 124, respectively.

Importantly, the two lifetimes remained unchanged. From the short decaying

component, attributed to complexed 99:124, the rate of electron transfer was

estimated as 2.8 x 10-9 s-1. This is in good agreement with the electron transfer rate

obtained from the steady-state fluorescence experiments (7.6 x 109 s-1). In a control

experiment, redox- and photoinactive 115 was added to 99:124. The pre-exponential

factors were completely reverted, namely the one of the short-lived component

decreased gradually and finally disappeared while, that of the long-lived component

increased likewise.

Figure 62: Normalized preexponential factors of the two lifetimes observed by time correlated

single photon counting (TCSPC) as a function of fullerene derivative 124 and dendron 115

equivalents.


92

Finally, we turned to transient-absorption measurements to find spectroscopic and

kinetic evidence in support to the hypothesized electron transfer. Representative

femtosecond time-resolved absorption spectra, recorded after a 150 fs laser pulse at

420 nm of ortho-dichlorobenzene solutions of 124, are displayed in Figure 63. The

spectra, as obtained at time delays shortly after the laser pulse, revealed broadly

absorbing features between 600 and 1100 nm. Superimposed onto that are features

of transient bleach, especially around 420 and 550 nm. The latter correspond to the

loss of ground state absorption. The singlet excited state (ESinglet = 2.0 eV) decays

slowly (4.8 x 108 s-1) to the

energetically low-lying triplet

excited state (ETriplet = 1.53

eV) via intersystem crossing

(φTriplet = 0.88). In terms of

spectral characteristics of the

later, a maximum at around

840 nm should be considered.

Figure 63. Differential absorption spectrum obtained by femtosecond flash photolysis (420 nm) of Zn-porphyrin 99

in argon-saturated ODCB with time delays of 2 and 2892 ps.

Next, transient absorption measurements were carried out with 99:124 and were

compared with the spectra of 99. At early time delays, transient absorption spectra of

99:124 are practically identical with those of 99. However, at time delays of 100 ps

the fingerprint absorptions of the one-electron oxidized Zn-porphyrin radical cation

and of the one-electron reduced fullerene radical anion appear at 680 nm and 1030

nm, [50,130,131] respectively. This radical ion pair features decay over a time period of 3

ns to recover quantitatively the singlet ground state without populating any triplet

excited states. In summary, electron transfer is responsible for the fast deactivation

of the photoexcited Zn-porphyrin and, in turn, affords the formation of the radical ion

pair state. Analyzing the kinetics of the time absorption profiles we derive rate

constants for charge separation of 9.0 x 109 s-1 and for charge recombination of 7.8 x

108 s-1. Notably good is the agreement between the charge separation rate


93

determined by steady-state fluorescence (7.6 x 109 s-1) and transient absorption

measurements (9.0 x 109 s-1).

Complementary nanosecond transient measurements, performed with 532 nm laser

excitation of different mixtures of 99:124, shed further light into the charge

recombination process. All the

spectra are characterized by

strong triplet-triplet

absorptions at 710 nm, which

correspond to that of the

fullerene triplet excited state.

We must assume the

fullerene triplet excited state,

without, however giving rise to

any radical ion pair features

neither at 680 nor 1030 nm. Figure 64. Differential absorption changes obtained by

femtosecond flash photolysis (420 nm) of 99:124 in argon-saturated ODCB with time delays of 1 and 97 ps.

The fullerene triplet excited state probably originated from a locally excited state of

free, uncomplexed fullerene. Implicit is in line with the femtosecond experiments that

charge recombination occurs on a time scale faster than our nanosecond

experiments, that is, 6 ns.

SUMMARY AND CONCLUSIONS

94

4. SUMMARY AND CONCLUSIONS In the present research work a new family of di- and tetra-substituted

tetraphenylporphyrin derivatives equipped with the Hamilton receptor recognition

motif were synthesized.

The self-assembly of the Hamilton receptor functionalized porphyrins 93, 99 and 106

with the complementary cyanuric acid derivatives 112 - 117 via multiple hydrogen

bonding led to the formation of novel supramolecular architectures which were

investigated by 1H NMR titration experiments and CD spectroscopy.

The photophysical properties of the self-assembled, hydrogen bonded

superstructures were studied by steady state fluorescence titration experiments and

time resolved absorption spectroscopy (femtosecond and nanosecond flash

photolysis). The tetra-substituted Hamilton receptor functionalized porphyrin 93 was

synthesized by a four-fold esterification of the porphyrin 92 with the Hamilton

receptor derivative 45 under EDC/DCC experimental conditions. The insolubility of 93

in nonpolar, aprotic solvents such as CHCl3, C2H2Cl2 or CH2Cl2 did not allow the

study of the self-assembly processes with the complementary cyanurates 112 - 117

and the further calculation of the kinetic data by means of titration experiments

monitored by NMR, UV/Vis or CD spectroscopies. However, a complete solubilization

of 93 in those solvents was observed after the addition of four equivalents of the

cyanurates 112 - 117 and confirmed by the stepwise deepening of the solution’s

colour upon the formation of the supramolecular porphyrin-dendrimers 118 - 123.

The clearly separated electronic absorptions of the porphyrin Hamilton receptor,

namely λ= 300 and 420 nm were utilized for the determination of chirality transfer

resulting from the complexation of the chiral depsipeptide dendrons 112 - 117, by CD

spectroscopy. One equiv. of the Hamilton receptor porphyrin 93 was mixed with 4

equiv. of the corresponding depsipeptide dendron 112 - 117 in CHCl3 solvent and the

solutions were stirred overnight to guarantee the successful formation of the

supramolecular complexes 118 - 123. The supramolecular first generation porphyrin

dendrimers revealed no detectable CD effect in the absorption regions of the

Hamilton receptor porphyrin which can be explained by a very weak chirality transfer

attributed to the presence of only two stereogenic centres in each depsipeptide

cyanurate 112 and 113. In the cases of the supramolecular second to third

generation complexes, the chirality transfer to the Hamilton receptor porphyrin was


95

demonstrated by CD spectroscopy. The intensities of the CD absorptions in the

Hamilton receptor porphyrin region of the complexes (300 nm and 420 nm) were

found to be inversely proportional to the generation number of the dendrons pointing

to a size-dependent cooperativity regarding the four-fold complexation of the

cyanurate guests. The second generation dendrons 114 and 115 experienced a

more effective binding compared to their bulkier third generation counterparts 116

and 117. A pronounced cooperativity during the self-assembly to the second

generation 93:L4 complexes (L= 114 or 115) was considered to be the reason for the

diastereoselective formation of a preffered chiral propeller-like Λ or Δ conformation.

Complexation of the Hamilton receptor functionalized porphyrin 93 with the

enantiomerically pure dendrons 114 (all-R) is expected to result in the formation of

two diastereomers such as Λ-93:1144 (all-R) and Δ-93:1144 (all-R). In a similar

manner, the utilization of dendron 115 (all-S) will furnish upon complexation with

porphyrin 93 the diastereomers Λ-93:1154 (all-S) and Δ-93:1154 (all-S). The

preferential formation of an energetically favoured diastereomer, in each case, would

lead to an increased intensity of the CD absorptions as was indeed observed for the

supramolecular aggregates 120 and 121. This phenomenon was found to be much

less pronounced for the self-assembly processes involving the third generation

cyanurates as the fourth complexation step was less favored due to the increased

sterical demands of the ligands.

The cis- and trans substitution pattern of the Hamilton receptor bi-functionalized

porphyrins 99 and 106 in conjunction with the rigid structure of the porphyrin core

offer a well defined geometry of the host moieties. Therefore, these molecular

building blocks represent attractive molecular units towards the construction of novel

supramolecular architectures via self-assembly processes with complimentary

guests. For example, the combination of a cis-symmetric Hamilton receptor

functionalized porphyrin and a complementary trans-symmetric porphyrin cyanurate

is very likely to result in rectangular architectures depending on the flexibility of the

supramolecular complex. In this work, several attempts to purify a complimentary

trans-symmetric porphyrin bis-cyanurate failed due to the high polarity and low

solubility of the target compound. The self-assembly of the cis- and trans-symmetric

Hamilton receptor functionalized Zn-porphyrins 99 and 106 with the first to third

generation depsipeptide dendrons 113, 115 and 116 led to the formation of

supramolecular 1:2 complexes and 1H NMR titration experiments allowed the


96

calculation of the association constants. In general, the self-assembly of the

supramolecular first to third generation complexes with trans-geometry of the

Hamilton receptors was found to be much more pronounced compared to their cis-

symmetric analogues. The largest complex stability and pronounced cooperativity

was observed for the 1:2 complexes involving the first generation dendron 113,

clearly reflected in the values of the first and second binding step (K1 and K2) and the

Hill constants (nH). The association constants K2 were found to decline with

increasing the generation number of the depsipeptide dendrons, a fact attributed to

the increasing sterical demands of the cyanurates. As a consequence, only 70 % of

106 and 45 % 99 were involved in a C:L2 complex (C= 99 or 106, L= 116) with a

stoichiometric ratio of 1:2. The 1:2 stoichiometry of the supramolecular first to third

generation aggregates was confirmed by Job’s plot analysis.

Furthermore, supramolecular aggregates between the Hamilton receptor

functionalized Zn-porphyrins 99 and 106 and the fullerene derivatives 124 and 125

as ligands were subjected to a series of photophysical investigations. Fluorescence

titrations allowed the calculation of the association constants which were in excellent

agreement with the estimated values derived from 1H NMR titration analysis. On the

contrary to earlier results, the self-assembly between the Hamilton receptor Zn-

porphyrin 106 and dendrofullerene 124 in a mixture of ODCB/pyridine 1000:1 as a

solvent was found to be much less pronounced. Weaker binding in the presence of

pyridine can be considered as a reason. A similar hypothesis might also explain the

observed weak self-assembly between Zn-porphyrin 99 and fullerene derivative 125

in CHCl3/CS2 5:1. Furthermore, the NMR spectra of 106 and its precursors 87 and

104 in CDCl3 solvent showed unresolved and broad resonance signals. This

phenomenon was not observed after the addition of one drop of deuterated pyridine

to solutions of 87 in CDCl3. Since the free base porphyrin 78 and Ni-analogue 91 (no

vacant coordination sites) gave rise to common NMR spectra, intermolecular

aggregation via the free axial coordination site of the Zn2+ ion was considered as the

reason. A series of photophysical experiments - ranging from steady-state and time-

resolved fluorescence experiments to transient absorption measurements on the

femtosecond and nanosecond time scale - provided decisive confirmation of the

nature of electron donor acceptor interactions as they are operative between Zn-

porphyrin 99 and dendrofullerene 124 in the supramolecular assembly 99:124.

ZUSAMMENFASSUNG UND ERGEBNISSE

97

5. ZUSAMMENFASSUNG UND ERGEBNISSE In der vorliegenden Arbeit wurde eine neue Klasse von Hamiltonrezeptor- und

Cyanursäure-funktionalisierten Tetraphenylporphyrinderivaten synthetisiert.

Die Komplexierung der Hamiltonrezeptor funktionalisierten Porphyrine 93, 99 und

106 mit den komplementären Cyanursäurederivaten 112 - 117 führte zur Ausbildung

von neuartigen, über multiple Wasserstoffbrückenbindungen stabilisierten,

supramolekularen Porphyrindendrimeren, welche durch 1H NMR

Titrationsexperimente und CD Spektroskopie untersucht wurden.

Die photophysikalischen Eigenschaften der supramolekularen Porphyrin-

fullerendendrimere wurden zusätzlich durch Steady State

Fluoreszenztitrationsexperimente und zeitaufgelöste Absorptionsspektrometrie

(Femtosekunden- und Nanosekunden-Blitzlichtphotolyse) untersucht.

Das vierfach Hamiltonrezeptor funktionalisierte Porphyrin 93 wurde durch eine

DCC/EDC Veresterungsreaktion zwischen dem Porphyrinderivat 92 und der

Hamiltonrezeptorverbindung 45 dargestellt. Die Isolierung des Hamiltonrezeptor

funktionalisierten Porphyrins 93 war aufgrund der eingeschränkten Löslichkeit (nur

löslich in THF, DMF und DMSO) und der hohen Polarität dieser Verbindung nur

durch wiederholte Säulenchromatographie und anschliessende präparative HPLC

realisierbar. Ebenso war die weitere Untersuchung der Self-assembly Prozesse mit

den komplementären Depsipeptidcyanuraten 112 - 117 und die entsprechende

Berechnung der kinetischen Daten mit Hilfe von NMR-, UV/Vis- oder CD-

Spektroskopietitrationsexperimenten aufgrund der Unlöslichkeit von 93 in

nichtpolaren, aprotischen Lösemitteln wie CHCl3, C2H2Cl4 oder CH2Cl2 nicht möglich.

Durch die Zugabe von vier Äquivalenten der Depsipeptidcyanurate 112 - 117 konnte

jedoch eine komplette Solubilisierung von 93 in diesen Lösemitteln erreicht werden.

Mit zunehmender Konzentration der Cyanurate konnte ein Farbwechsel der Lösung

von farblos nach kirschrot beobachtet werden, was auf die Ausbildung der löslichen

supramolekularen Porphyrindendrimere 118 - 123 zurückzuführen war. Die

Komplexierung der chiralen Depsipeptiddendronen 112 - 117 führte zu

Chiralitätstransfers auf das achirale Hamiltonrezeptor funktionalisierte Porphyrin

welche durch CD-Spektroskopie im charakteristischen, elektronischen

Absorptionsbereich von 93 (λ = 300 und 420 nm) aufgeklärt werden konnten. Ein

Äquivalent des Hamiltonrezeptor funktionalisierte Porphyrins wurde in CHCl3


98

suspendiert und nach der Zugabe von vier Äqivalenten des jeweiligen

Depsipeptiddendrons über Nacht gerührt um eine vollständige Ausbildung der

supramolekularen Komplexe 118 - 123 zu gewährleisten. Für die supramolekularen

Porphyrindendrimere der ersten Generation 118 und 119 konnte jedoch kein CD

Effekt beobachtet werden, was auf sehr schwache Chiralitätstransferprozesse

zurückzuführen ist. In diesem Fall, war die durch zwei stereogene Zentren

verursachte Chiralität der Depsipeptidcyanurate 112 und 113 für einen

Chiralitätstransfer auf den achiralen Hamiltonrezeptorbaustein nicht ausreichend. Für

die supramolekularen Systeme der zweiten bis dritten Generation konnte der

Chiralitätstransfer durch CD Spektroskopie nachgewiesen werden. Mit steigender

Generationszahl der Gastmoleküle konnte eine Abnahme der CD-Effekte im

Absorptionsbereich des Hamiltonrezeptorporphyrinbausteins (300 und 420 nm)

beobachtet werden. Diese Tatsache ist möglicherweise auf eine größenabhängige

Kooperativität zurückzuführen, da die vierfache Komplexierung der

Cyanuratgastmoleküle an der Peripherie von 93 eine zunehmde sterische

Beanspruchung verursachen sollte. Die Dendronen der zweiten Generation 114 und

115 wurden im Vergleich zu ihren sterisch anspruchsvolleren Analoga der dritten

Generation effektiver an das Hamiltonrezeptor funktionalisierte Porphyrin gebunden.

Möglicherweise führte die ausgeprägt, positive Kooperativität während des Self-

assemblys der 93:L4 Komplexe der zweiten Generation zur diastereoselektiven

Bildung einer bevorzugten propellerartigen Λ oder Δ Konformation. Somit sollte die

Komplexierung des Hamiltonrezeptor funktionalisierten Porphyrins 93 mit den

enantiomerenreinen Dendronen 114 (reine R-Konfig.) zur Bildung von zwei

Diastereomeren Λ-93:1144 und Δ-93:1144 (reine R-Konfig.) führen. In gleicher Weise

wären im Falle der Komplexierung mit 115 (reine S-Konfig.) die Diastereomere Λ-

93:1154 und Δ-93:1154 (reine S-Konfig.) zu erwarten. Folglich würde die bevorzugte

Ausbildung eines energetisch begünstigten Diastereomers zu einer

Intensitätszunahme der CD-Absorptionen führen was im Fall der supramolekularen

Aggregate 120 und 121 beobachtet werden konnte. Dieses Phänomen war für die

Self-assembly Prozesse mit den Cyanuraten der dritten Generation weniger stark

ausgeprägt da der vierte Komplexierungsschritt vermutlich durch den vergrößerten

sterischen Anspruch der Dendronen 116 und 117 erschwert wird.

Das cis- und trans-Substitutionsmuster der zweifach Hamiltonrezeptor

funktionalisierten Porphyrine 99 und 106 in Kombination mit der unflexiblen Struktur


99

des Porphyrinkerns ermöglichen eine gut definierte Geometrie der Wirtmoleküle. Aus

diesem Grund stellen diese Verbindungen attraktive, molekulare Bausteine für den

Aufbau neuartiger, supramolekularer Architekturen über Self-assembly mit den

entsprechenden, komplementären Gastmolekülen dar. Beispielsweise sollte die

Aggregation eines cis-symmetrischen Hamiltonrezeptor funktionalisierten Porphyrins

mit einem komplimentären trans-symmetrischen Porphyrin-bis-cyanurat zu

rechteckigen supramolekularen Strukturen führen deren Geometrie ebenso von der

Flexibiltät der supramolekularen Komplexe beeinflusst werden sollten. In dieser

Arbeit, waren die Versuche ein solches trans-symmetrisches Porphyrin-bis-cyanurat

zu isolieren aufgrund der hohen Polarität und der geringen Löslichkeit dieser

Verbindungen erfolglos. Das Self-assembly der cis- und trans-symmetrischen

Hamiltonrezeptor-Zn-porphyrine 99 und 106 mit den Depispeptiddendronen der

ersten bis zur dritten Generation 113, 115 und 116 führte zur Ausbildung von

supramolekularen 1:2 Komplexen, deren Assoziationskonstanten anhand von 1H

NMR Titrationsexperimenten ermittelt wurden. Im allgemeinen war das Self-

assembly der supramolekularen trans-symmetrischen Komplexe der ersten bis zur

dritten Generation stärker ausgeprägt als bei den entsprechenden cis-Analoga. Die

größten Komplexstabilitäten und ausgeprägten Kooperativitäten konnten für die 1:2

Komplexe der ersten Generation beobachtet werden, was sich deutlich in den

Assoziationskonstanten für den ersten und zweiten Komplexierungsschritt (K1, K2)

und den Hill Konstanten wiederspiegelte. Die Bindungskonstanten K2 verringerten

sich mit zunehmender Größe der Depsipeptiddendronen was auf die zunehmenden

sterischen Ansprüche der Cyanuratgäste zurückzuführen war. Folglich waren bei

einem stöchiometrischen Verhältnis von 1:2 nur 70 % von 106 und 45 % von 99 an

einem C:L2 Komplex (C = 99 oder 106, L = 116) beteiligt. Die postulierten 1:2

Stöchiometrien der supramolekularen Aggregate der ersten bis dritten Generation

wurden durch Job’s Plot Analyse bestätigt.

Desweiteren wurden supramolekulare Aggregate der Hamiltonrezeptor-Zn-

porphyrine 99 und 106 mit den Fullerenderivaten 124 oder 125 einer Reihe von

photophysischen Experimenten unterzogen. Fluoreszenztitrationsexperimente

ermöglichten die Bestimmung der Assoziationskonstanten, welche in exzellentem

Masse mit denen durch 1H NMR-Titrationsanalyse ermittelten Werten

übereinstimmten. Im Gegensatz zu den früheren Ergebnissen war aber hier das Self-

assembly des Hamiltonrezeptor-Zn-porphyrins 106 mit dem Dendrofulleren 124 in


100

einer Mischung aus ODCB/Pyridin 1000:1 als Lösungsmittel weniger stark

ausgeprägt. Eine schwächere Komplexierung von 124, verursacht durch die

Gegenwart von Pyridin, kann als mögliche Ursache in Betracht gezogen werden.

Eine ähnliche Erklärung könnte auch im Fall des gering ausgeprägten Self-assembly

von Zn-porphyrin 99 und Fullerenderivat 125 in CHCl3/CS2 5:1 als Lösungsmittel in

Frage kommen. Desweiteren wiesen die NMR Spektren von 106 und seinen

Vorstufen 87 und 104 in CDCl3 unaufgelöste, breite Resonanzsignale auf. Dieses

Phänomen konnte durch die Zugabe eines Tropfens von deuteriertem Pyridin zu

Lösungen von 87 in CDCl3 aufgehoben werden. Da das metallfreie Porphyrin 78 und

das zu 87 analoge Ni-Porphyrin 91 (keine freien axialen Koordinationsstellen) die zu

erwarteten NMR Spektren aufwiesen, lag hier wahrscheinlich eine intermolekulare

Aggregation über die freie, axiale Koordinationsstelle des Zn2+ Ions vor. Desweiteren

konnten wichtige Informationen über den Charakter der Donor-Akzeptor

Wechselwirkungen zwischen 99 und 124 durch Steady-state Fluoreszenz- und

zeitaufgelöste Fluoreszenzexperimente in Kombination mit

Transientabsorptionsspektroskopie (Nano- bzw. Femtosekunden Zeitauflösung)

gewonnen werden.

EXPERIMENTAL PART

101

6. EXPERIMENTAL PART

6.1. Instruments and Methods UV/Vis spectra were recorded on a UV-3102 PC UV-Vis-NIR Scanning

Spectrophotometer, Shimadzu Corporation, Analytical Instruments Division, Kyoto,

Japan.

NMR spectra were recorded on JEOL JNM EX 400, JEOL JNM GX 400, JEOL 500,

Bruker Avance 300 and Bruker Avance 400 spectrometer. The chemical shifts are

given in ppm relative to the solvent peak as a standard reference. The resonance

multiplicities are indicated as s (singlet), d (doublet), t (triplet), q (quartet) and m

(multiplet), unresolved signals as broad (br) or very broad (v. br).

IR spectra were recorded on a REACT-IRTM 1000 spectrometer with an ATR

DiComp detector, Asi Applied Systems.

Elemental analysis was performed on an EA 1110 CHNS, CE Instruments.

Circular dichroism spectra were recorded on a JASCO J 710.

Analytical HPLC was performed using a LC-10 AT pump, a SIL-10 A autoinjector, a

CBM 10 A BUS-Modul and a SPD-M 10 A photomultiplier detector, Shimadzu

Corporation, Analytical Instruments Division, Kyoto, Japan.

Preparative HPLC was performed using a LC-8A pump, a SIL-10 A autoinjector, a

CBM 10 A BUS-Modul, a SPD-10A UV detector and a FRC-10A fraction collector,

Shimadzu Corporation, Analytical Instruments Division, Kyoto, Japan.

Mass Spectra were measured with a Micromass Lab Spec (FAB) on a Finnigan MAT

900 spectrometer with 3-nitrobenzylalcohol as a matrix.

EXPERIMENTAL PART

102

MALDI TOF Mass spectra were measured on a Shimadzu Axima Confidence

spectrometer (Version 3.04, Kratos Analytical) using a N2 UV Laser with a

wavelength of 337 nm. DHTB, SIN, DIT or DCTB were used as matrices.

Theoretical calculations were performed using the programs Hyperchem[88] and

Spartan.[89]

6.2. Chemicals Commercially available chemicals were purchased from Aldrich, Fluka, Sigma and

Acros Organics. Solvents were dried using standard techniques[132] and dry DMF was

obtained from Acros. Prior to use, CHCl3, EtOAc and CH2Cl2 were freshly evaporated

over potassium carbonate to avoid protonation of the porphyrin compounds.

Analytical HPLC and CD spectroscopy were performed using HPLC grade solvents

purchased from Acros organics.

Column chromatography was performed using Merck silica Gel 60 (230 - 400

mesh, 0.04 - 0.063 nm) and ICN silica Gel 32 - 63 (60 Å).

Thin Layer Chromatography (TLC) was performed using Riedel-de-Haën silica gel

60 F254 and Merck silica gel 60 F254 on aluminium foils, detection at 254 nm via UV

lamp.

6.3. Experimental Details

The following substances were synthesized and characterized according to the

literature.

• Hydroxyl-substituted Hamilton receptor derivative 45[22,69]

• N-(6-aminopyridin-2-yl)-3,3-dimethylbutanamide 42[20]

• 5-iodobenzene-1,3-dioic acid 41[70,71]

• N-(4-Iodophenyl)isocyanuric acid 101[97]

• 1-(6-hydroxyhexyl)-[1,3,5]-triazin-2,4,6-trion 49 and 1-(6-bromohexyl)-1,3,5

triazinane-2,4,6-trione 52[69]

EXPERIMENTAL PART

103

• Dipyrromethanes 73[75] and 77[78]

• 5,10,15,20-{4-[2-(trimethylsilyl)ethynyl]phenyl}porphyrin 68[74]

• Zinc-5,10,15,20-tetrakis{4-[2-(trimethylsilyl) ethynyl] phenyl}porphyrin 84[98]

Synthesis of the iodine substituted Hamilton receptor derivative 48:

Diacid 41 (3.36 g, 11.51 mmol) was suspended in 60

mL of SOCl2 and 1 mL of dry DMF was added under

inert conditions. The reaction mixture was heated at

reflux for 6 h. The excess of SOCl2 was distilled off

and the oily residue was kept under high vacuum for

60 min. The crude dichloride was used without

further purification. A mixture of NEt3 (3.20 mL, 6.84

mmol) and compound 42 (5.97 g, 28.81 mmol) in 60 mL dry THF were added

dropwise to the solution of the dichloride in 50 mL dry THF at 0 ºC and the reaction

mixture was stirred for 72 h at RT. The reaction mixture was diluted with 200 mL

water and 200 mL EtOAc and the phases were separated. The aqueous layer was

extracted twice with 150 mL EtOAc and the combined organic layers were dried over

MgSO4. The solution was filtrated, concentrated to dryness and purified by flash

column chromatography (SiO2, CH2Cl2/EtOAc 2:1, Rf = 0.65). Yield: 5.63 g (73 %), slightly yellow solid. 1H NMR (300 MHz, CDCl3, 25 ºC): δ = 1.09 (s, 18 H, CH3), 2.26 (s, 4 H, CH2), 7.68

(dd, 2 H, Py), 7.88 (d, 3JH,H = 8.1 Hz, 2 H, Py), 7.95 (d, 3JH,H = 8.1 Hz, 2 H, Py), 8.04

(br, 2 H, CONH), 8.31 (s, 3 H, Bn), 8.50 (br, 2 H, CONH) ppm. 13C NMR (75 MHz, CDCl3, 25 ºC): δ = 29.77 (CH3), 31.38 (CCH3), 51.47 (CH2), 94.77

(Bn), 102.47, 106.67 (Py), 110.43, 136.11, 139.65 (Bn), 140.88, 148.86, 149.79 (Py),

162.94, 170.65 (C=O) ppm.

EA: calc. (%) for C30H35IN6O4 (670.54) = C 53.74, H 5.26, I 18.39, O 9.54, N 12.53;

found: C 54.07, H 5.47, N 12.17.

MS (FAB): m/z = 671 [M+H]+.

UV/Vis (CH2Cl2): [λ/nm] (ε/lmol-1cm-1) 303 (29100).

IR (ATR): νmax = 2971, 2360, 1738, 1584, 1518, 1447, 1365, 1300, 1230, 1145, 797

cm-1.

EXPERIMENTAL PART

104

Synthesis of 6-(2,4,6-trioxo-triazinan-1-yl)hexyl 4-formylbenzoate 51:

3.19 g (26.10 mmol) DMAP, 3.53 g (26.10

mmol) HOBT and 5.39 g (26.10 mmol) DCC

were added to a solution of 1.50 g (6.54 mmol)

1-(6-hydroxyhexyl)-[1,3,5]-triazin-2,4,6-trione

and 0.65 g (4.35 mmol) 4-formyl benzoic acid in 40 mL dry THF at 0 °C. The reaction

mixture was stirred for 2 h at this temperature and was allowed to proceed for further

12 h at RT. The solvent was removed under reduced pressure and the remaining

solid was dissolved in THF. The precipitated DCU was filtrated and the filtrate was

evaporated to dryness. For complete removal of DCU the remaining solid was

washed two times with cold CH2Cl2.The product was purified by column

chromatography (SiO2, EtOAc/CHCl3 1:1, Rf = 0.55).

Yield: 0.90g (57 %), white solid. 1H NMR (400 MHz, acetone-d6, 25 °C): δ = 1.42 (m, 2 H, CH2), 1.52 (m, 2 H, CH2),

1.65 (m, 2 H, CH2), 1.80 (m, 2 H, CH2), 3.77 (t, 3JH,H = 7.32 Hz, 2 H, NCH2), 4.35 (d, 3JH,H = 6.59 Hz, 2 H, OCH2), 8.06 (d, 3JH,H = 8.54 Hz, 2 H, Bn), 8.20 (d, 3JH,H = 8.17

Hz, 2 H, Bn), 10.15 (s, 1 H, COH). 13C NMR (100.5 MHz, acetone-d6, 25 °C): δ = 26.37 (CH2), 26.94 (CH2), 29.23

(CH2), 41.57 (NCH2), 66.06 (OCH2), 130.26, 130.77, 136.07, 140.40 (Bn), 148.80,

150.46, 165,98 (C=O), 192.77 (COH).

MS (FAB): m/z = 362 [M]+.

Synthesis of 5-[4-(methoxycarbonyl)phenyl]-10,15,20-tris(tert-butylphenyl)-porphyrin 59:

TFA (5.70 mL, 75.00 mmol) was added to a

solution of 4-tert-butylbenzaldehyde 57 (1.88 mL,

11.25 mmol), methyl-4-formylbenzoate (615.00 mg,

3.75 mmol) and pyrrole (1.03 mL, 15.00 mmol) in

375 mL of CH2Cl2. The reaction mixture was stirred

at RT for 1 h. After neutralization with NEt3 (6.85

mL, 48.75 mmol) DDQ (2.19 g, 9.40 mmol) was

EXPERIMENTAL PART

105

added and the solution was stirred for further 2 h at RT. The crude reaction mixture

was concentrated and filtrated (SiO2, CH2Cl2). The porphyrin isomers were separated

by repeated column chromatography (SiO2, CH2Cl2/hexane 9:1, Rf = 0.62). Yield: 560

mg (18 %), dark violet powder. 1H NMR (300 MHz, CDCl3, 25 °C): δ = - 2.68 (br, 2 H, pyrrole NH), 1.65 (s, 27 H,

CH3), 4.15 (s, 3 H, OCH3), 7.80 (d, 3JH,H = 8.3 Hz, 6 H, Bn), 8.17 (d, 3JH,H = 8.4 Hz, 6

H, Bn), 8,39 (d, 3JH,H = 9.0 Hz, 2 H, Bn), 8.47 (d, 3JH,H = 8.4 Hz, 2 H, Bn), 8.83 (d, 3JH,H = 5.1 Hz, 2 H, pyrrole), 8.94 (m, 6 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 31.69 (CH3), 34.84 (CCH3), 52.40 (OCH3),

118.15, 120.47, 120.76, 123.62, 127.68, 129.43, 134.45, 134.50, 139.03, 146.94,

150.51, 150.53 (Bn, meso-C), 167.39 (C=O) ppm.

EA: calc. (%) for C58H56N4O2 (841.09) x CH2Cl2 = C 76.52, H 6.31, Cl 7.66, O 3.46, N

6.05; found: C 77.75, H 6.20, N 6.08.

MS (FAB): m/z =842 [M+H]+.

UV/Vis (CH2Cl2): [λ/nm] (ε/lmol-1cm-1) 420.0 (415700), 517.0 (21600), 552.0 (9100),

648.0 (10.000).

IR (ATR): νmax = 2963, 2867, 2363, 1727, 1608, 1558, 1508, 1475, 1434, 1400,

1363, 1351, 1312, 1274, 1222, 1194, 1155, 1111, 1023, 993, 983, 968, 869, 850,

801, 760, 735, 712 cm-1.

Characterization of 5,15-bis[4-(methoxycarbonyl)phenyl]-10,20-bis(tert-butylphenyl)-porphyrin 60:

1H NMR (300 MHz, CDCl3, 25 °C): δ = -2.73 (br, 2

H, pyrrole NH), 1.63 (s, 18 H, CH3), 4.14 (s, 6 H,

OCH3), 7.79 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.14 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.83 (d, 3JH,H = 8.4 Hz, 4 H,

Bn), 8.49 (d, 3JH,H = 8.1 Hz, 4 H, Bn), 8.82 (d, 3JH,H =

4.8 Hz, 4 H, pyrrole), 8.94 (d, 3JH,H = 4.8 Hz, 4 H,

pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 31.67 (CH3),

34.89 (CCH3), 52.42 (OCH3), 118.74, 120.80, 123.68, 127.88, 129.52, 134.39,

134.59, 138.82, 147.05, 150.65 (Bn, meso-C), 167.34 (C=O) ppm.

EXPERIMENTAL PART

106

EA: calc. (%) for C56H50N4O4 (842.38) x 0.3 CH2Cl2 = C 77.86, H 5.87, Cl 2.45, O

7.37, N 6.45; found: C 77.57, H 6.22, N 6.07.

MS (FAB): m/z = 844 [M+H]+.


591.0 (7600), 647.0 (7800).

IR (ATR): νmax = 2970, 2952, 2360, 2342, 1729, 1608, 1474, 1457, 1433, 1397, 1365,

1312, 1272, 1228, 1217, 1110, 1023, 994, 982, 967, 852, 815, 803, 786, 760, 737,

712 cm-1.

Characterization of 5,10-bis[4-(methoxycarbonyl)phenyl]-15,20-bis(tert-butylphenyl)-porphyrin 61:

1H NMR (300 MHz, CDCl3, 25 °C): δ = -2.68 (br, 2

H, pyrrole NH), 1.65 (s, 18 H, CH3), 4.15 (s, 6 H,

OCH3), 7.80 (d, 3JH,H = 8.1 Hz, 4 H, Bn), 8.16 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.37 (d, 3JH,H = 8.7 Hz, 4 H,

Bn), 8.47 (d, 3JH,H = 9.0 Hz, 4 H, Bn), 8.87 (m, 4 H,

pyrrole), 8.96 (m, 4 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 31.62 (CH3),

34.86 (CCH3), 52.38 (OCH3), 118.47, 121.06,

123.63, 127.88, 129.52, 134.41, 134.55, 138.86, 146.96, 150.63 (Bn, meso-C),

167.28 (C=O) ppm.

EA: calc. (%) for C56H50N4O4 (842.38) x 0.3 CH2Cl2 = C 77.86, H 6.14, Cl 2.45, O

7.37, N 6.45; found: C 77.87, H 6.14, N 6.18.

MS (FAB): m/z = 843 [M+H]+.

UV/Vis (CH2Cl2): [λ/nm] (ε/lmol-1cm-1) 420.0 (437400), 516.5 (194500), 551.5

(10800), 591.0 (6400), 647.0 (6000).

IR (ATR): νmax = 3004, 2970, 2360, 2341, 1737, 1723, 1608, 1432, 1366, 1313,

1276, 1228, 1217, 1110, 1022, 981, 967, 805, 764, 738, 713 cm-1.

EXPERIMENTAL PART

107

Characterization of 5,10,15-tris(tert-butylphenyl)-20-(4-ethynylphenyl)-porphyrin 63:

1H NMR (300 MHz, CDCl3, 25ºC): δ = -2.76 (br, 2

H, NH), 1.55 (s, 27 H, CH3), 3.32 (s, 1 H, C≡CH),

7.75 (d, 3JH,H = 8.1 Hz, 6 H, Bn), 7.88 (d, 3JH,H = 8.1

Hz, 2 H, Bn), 8.15 (m, 8 H, Bn), 8.79 (d, 3JH,H = 6.0

Hz, 2 H, pyrrole), 8.88 (m, 6 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 ºC): δ = 30.15 (CH3),

34.89 (CCH3), 78.21, 83.73 (C≡C), 120.35, 120.56,

121.42, 123.62, 130.46, 134.47, 134.51, 139.06,

139.12, 139.22, 143.02, 150.42, 150.52 (Bn, meso-C) ppm.

EA: calc. (%) for C58H54N4 x 0.5 CHCl3 (807.08) = C 81.06, H 6.34, Cl 6.14, N 6.46;

found: 81.24, 7.64, N 5.02.

MS (FAB): m/z = 807 [M]+.


593.0 (3800), 656.0 (4000).

IR (ATR): νmax = 3273, 2925, 2360, 1739, 1475, 1351, 1217, 1107, 968, 851, 804,

736 cm-1.

Synthesis of 5,10-bis(tert-butylphenyl)-15,20-bis(4-ethynylphenyl)-porphyrin 65:

BF3•OEt2 (0.50 mL, 3.55 mmol) was added to a

solution of compound 57 (1.24 mL, 7.42 mmol), 62

(1.50 g, 7.42 mmol) and pyrrole (1.03 mL, 14.84

mmol) in 680 mL of CH2Cl2. The condensation

reaction was allowed to proceed for 1 h under the

exclusion of light. DDQ was added (2.53 g, 11.13

mmol) and the reaction mixture was stirred for 12 h

in the dark. The crude mixture was concentrated to

50 mL and filtrated over SiO2 using CH2Cl2 as

eluent. The purification of the porphyrin isomers was proved to be difficult due to the

similar polarity of the tert-butyl- and TMS- substituents and the reaction mixture was

subjected to the next reaction without further purification.

EXPERIMENTAL PART

108

The porphyrin mixture was dissolved in 60 mL of dry THF and a solution of TBAF in

THF (1M, 10.00 mL) was added dropwise. The reaction was allowed to proceed in

the dark for 24 h under inert conditions. The solution was concentrated to dryness,

the remaining residue was dissolved in 20 mL CH2Cl2, washed two times with an

aqueous solution of NaHCO3 (5%, 20 mL) and two times with 20 mL water. The

organic layer was dried over Na2SO4, filtrated and evaporated to dryness. Compound

65 was purified by repeated column chromatography (SiO2, CH2Cl2/Hexane 1:1, Rf =

0.36).

Yield 65.34 mg (3 %), dark violet powder. 1H NMR (300 MHz, CDCl3, 25ºC): δ = -2.80 (br, 2 H, NH), 1.55 (s, 18 H, CH3), 3.33

(s, 2 H, C≡CH), 7.75 (d, JH,H = 8.1 Hz, 4 H, Bn), 7.88 (d, JH,H = 7.8 Hz, 4 H, Bn), 8.15

(d, 8 H, Bn), 8.82 (m, 4 H, pyrrole), 8.90 (m, 4 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25ºC): δ = 31.66 (CH3), 34.88 (CCH3), 78.26, 83.65

(C≡C), 118.78, 120.81, 121.53, 123.63, 124.04, 130.48, 134.45, 138.94, 142.87,

150.60 (Bn, meso-C) ppm.

EA: calc. (%) for C56H46N4 x CH2Cl2 (775.00) = C 79.61, H 5.63, Cl 8.25, N 6.52;

found: C 80.61, H 7.99, N 4.27.

MS (FAB): m/z = 775 [M]+.


591.5 (3900), 647.5 (3200).

IR (ATR): νmax = 3272, 2955, 2926, 2858, 2360, 2341, 1738, 1605, 1499, 1475,

1396, 1365, 1352, 1266, 1217, 1108, 1072, 1053, 1023, 993, 983, 968, 880, 851,

804, 768, 736, 712 cm-1.

EXPERIMENTAL PART

109

Characterization of 5-tert-butylphenyl-10,15,20-tris(4-ethynylphenyl)porphyrin 66:

1H NMR (300 MHz, CDCl3, 25ºC): δ = -2.80 (br, 2

H, NH), 1.62 (s, 9 H, CH3), 3.33 (s, 3 H, C≡CH),

7.76 (d, 3JH,H = 8.4 Hz, 2 H, Bn), 7.89 (d, 3JH,H = 8.1

Hz, 6 H, Bn), 8.15 (d, 8 H, Bn), 8.84 (m, 6 H,

pyrrole), 8.92 (d, 3JH,H = 4.5 Hz, 2 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25ºC): δ = 31.66 (CH3),

34.89 (CCH3), 78.34, 83.61 (C≡C), 119.04, 119.24,

121.07, 121.62, 121.65, 123.68, 130.51, 134.45,

138.79, 142.64, 142.70, 150.69 (Bn, meso-C) ppm.

EA: calc. (%) for C58H38N4 x 0.25 CH2Cl2 (742.91) = C 83.35, H 5.01, Cl 4.51, N 7.31;

found: 83.82, 5.37, N 6.91.

MS (FAB): m/z = 743 [M]+.


591.5 (7600), 647.5 (6900).

IR (ATR): νmax = 3295, 1477, 1399, 1348, 1224, 1024, 966, 857, 802, 736, 711 cm-1.

Synthesis of 5,10-bis(3,5-dimethoxyphenyl)-15,20-bis{4-[2-(trimethylsilyl) ethynyl]phenyl}-porphyrin 71:

TFA (0.20 mL, 3.00 mmol) was added to a

solution of 62 (759.00 mg, 3.75 mmol), 67 (623.00

mg, 3.75 mmol) and pyrrole (0.50 mL, 7.50 mmol)

in 150 mL CH2Cl2. The reaction mixture was

stirred at room temperature for 1 h. After

neutralization with NEt3 (0.55 mL, 3.95 mmol),

DDQ (1.28 g, 5.63 mmol) was added and the

solution was stirred for further 2 h at RT. The

crude reaction mixture was concentrated and filtrated over SiO2 using CH2Cl2/EtOAc

9:1 as an eluent. The desired porphyrin compound was separated by repeated

column chromatography (SiO2, hexan/EtOAC 8:2, Rf = 0.42).

Yield: 144.00 mg (9 %) dark violet powder.

EXPERIMENTAL PART

110

e (SiO2, CH2Cl2/cyclohexane: 9/1, Rf = 0.43).

1H NMR (300 MHz, CDCl3, 25 °C): δ = -2.78 (br, 2 H, NH), 0.43 (s, 18 H, SiCH3),

4.00 (12 H, OCH3), 6.95 (t, 3JH,H = 2.1 Hz, 2 H, Bn), 7.44 (d, 3JH,H = 2.1 Hz, 4 H, Bn),

7.91 (d, 3JH,H = 8.1 Hz, 4 H, Bn), 8.21 (d, 3JH,H = 8.1 Hz, 4 H, Bn), 8.87 (br, 4 H,

pyrrole), 9.00 (br, 4 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 0.49 (SiCH3), 56.04 (OCH3), 96.01 (C≡C),

100.55 (Bn), 105.39 (C≡C), 114.26, 119.77, 120.46, 123.04, 130.78 134.79, 142.81,

144.30, 159.27 (Bn, meso-C) ppm.

EA: calc. (%) for C58H54N4O4Si2 (927.24) = C 75.13, H 5.87, N 6.04; found: C 72.29;

H 4.80, N 5.83.

MS (FAB): m/z = 927 [M]+.


590.0 (5300), 646.0 (3900).

IR (ATR): νmax = 3002, 2970, 2360, 2342, 2157, 1738, 1591, 1558, 1499, 1456,

1421, 1397, 1356, 1249, 1228, 1217, 1204, 1155, 1064, 1021, 974, 930, 859, 800,

762, 735 cm-1.

Synthesis of 10,20-bis(2,4,6-trimethoxyphenyl)-5,15-bis{4-[2-(trimethylsilyl) ethynyl]phenyl}-porphyrin 75:

BF3•OEt2 (1.40 mL, 11.00 mmol)

was added to a solution of 73

(6.99 g, 23.00 mmol) and 62 (4.51

g, 23.00 mmol) in 2.25 L CH2Cl2.

The reaction mixture was stirred at

room temperature for 1 h. DDQ

(7.58 g, 34.00 mmol) was added

and the solution was stirred for

further 2 h at RT. The crude

reaction mixture was concentrated

to 50 mL and filtrated over SiO2 using CH2Cl2 as an eluent. The desired porphyrin

compound was separated by repeated column chromatography and further purified

by recrystallization from CH2Cl2/pentan

Yield 1.27 g (11 %), dark violet powder.

EXPERIMENTAL PART

111

1H NMR (400 MHz, CDCl3, 25 ºC): δ = -2.67 (br, 2H, NH), 0.40 (s, 18 H, SiCH3), 3.50

(s, 12 H, OCH3), 4.10 (s, 6 H, OCH3), 6.59 (s, 4 H, Bn), 7.85 (d, 3JH,H = 7.5 Hz, 4 H,

Bn), 8.16 (d, 3JH,H = 7.5 Hz, 4 H, Bn), 8.75 (d, 3J = 4.9 Hz, 4 H, pyrrole), 8.84 (d, 3JH,H = 4.5 Hz, 4 H, pyrrole) ppm. 13C NMR (100.5 MHz, CDCl3, 25 ºC): δ = 0.08 (CH3), 55.59, 56.04 (OCH3), 90.88

(Bn), 95.21, 105.21 (C≡C), 112.39, 112.72, 117.98, 122.15, 130.17, 134.35, 142.86,

161.08, 161.89 (Bn, meso-C) ppm.

EA: calc. (%) for C60H58N4O6Si2 (987.30) = C 72.99, H 5.92, N 5.67, O 9.72, Si 5.69;

found: C 72.50, H 6.09, N 5.69.

MS (FAB): m/z = 987 [M]+.


592.0 (6000), 649.0 (3100).

IR (ATR): νmax = 3004, 2970, 2362, 2342, 2156, 1738, 1648, 1636, 1606, 1584,

1542, 1521, 1508, 1498, 1457, 1435, 1412, 1365, 1352, 1338, 1249, 1225, 1205,

1186, 1153, 1127, 1060, 982, 966, 951, 862, 844, 798, 760, 740, 712 cm-1. Synthesis of 10,20-bis[4-tert-butyl-2,6-(methoxymethyl)phenyl]-5,15-bis{4-[2-(trimethylsilyl)ethynyl]phenyl}-porphyrin 78

TFA (1.00 mL, 13.10 mmol) was

added to a solution of 77 (3.00 g,

8.19 mmol) and 62 (1.66 g, 8.19

mmol) in 655 mL CH2Cl2. The

reaction mixture was stirred at

room temperature for 1 h. After

neutralization with NEt3 (2.40 mL,

17.03 mmol) DDQ (2.79 g, 12.28

mmol) was added and the solution

was stirred for further 2 h at room

temperature. The crude reaction mixture was concentrated and filtrated over SiO2

using CH2Cl2/ EtOAc 95:5 as an eluent. The desired porphyrin isomer was separated

by repeated column chromatography (SiO2, CH2Cl2, Rf = 0.22).

Yield: 448.00 mg (10 %), violet powder.

EXPERIMENTAL PART

112

1H NMR (400 MHz, CDCl3, 25 °C): δ = -2.67 (br, 2 H, pyrrole NH), 0.39 (s, 18 H,

SiCH3), 1.65 (s, 18 H, CH3), 2.78 (s, 12 H, OCH3), 3.93 (s, 8 H, CH2), 7.89 (m, 8 H,

Bn), 8.17 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.70 (d, 3JH,H = 4.8 Hz, 4 H, pyrrole), 8.78 (d, 3JH,H = 4.8 Hz, 4 H, pyrrole) ppm. 13C NMR (100.5 MHz, CDCl3, 25 °C): δ = 0.47 (SiCH3), 32.12 (CH3), 35.65 (CCH3),

58.51 (OCH3), 73.45 (CH2), 96.11, 105.34 (C≡C), 115.79, 119.56, 122.87, 123.08,

130.84, 134.87, 135.39, 139.93, 142.40, 152.46 (Bn, meso-C) ppm.

EA: calc. (%) for C66H78N4O4Si2 x 1.5 CH2Cl2 (1095.56) = C 69.48, H 6.31, Cl 9.12, N

4.80, O 5.48, Si 4.81; found: C 69.51, H 7.40, N 4.65.

MS (FAB): m/z = 1095 [M]+.


592.0 (5300), 647.0 (3800).

IR (ATR): νmax = 2970, 2360, 2342, 2157, 1738, 1474, 1457, 1365, 1251, 1228,

1217, 1205, 1103, 1022, 981, 967, 862, 847, 802, 761, 741, 714 cm-1. Synthesis of Zinc-5-[4-(methoxycarbonyl)phenyl]-10,15,20-tris(tert-butylphenyl)-porphyrin 79:

Zn(OAc)2 dihydrate (117.43 mg, 535.02 μmol) was

added to a suspension of 59 (150.00 mg, 178.34

μmol) in 50 mL of THF. The reaction mixture was

stirred at RT for 12 h. The solution was

concentrated to dryness and purified by column

chromatography (SiO2, CH2Cl2, Rf = 0.66). Yield: 148.10 mg (92 %), pink powder.

1H NMR (400 MHz, CDCl3, 25 °C): δ = 1.61 (s, 27 H, CH3), 4.10 (s, 3 H, OCH3), 7.73

(d, 3JH,H = 8.0 Hz, 6 H, Bn), 8.12 (d, 3JH,H = 8.1 Hz, 6 H, Bn), 8.30 (d, 3JH,H = 8.1 Hz,

2 H, Bn), 8.39 (d, 3JH,H = 8.2 Hz, 2 H, Bn), 8.79 (m, 2 H, pyrrole), 8.90 (m, 6 H,

pyrrole) ppm. 13C NMR 100.5 MHz, CDCl3, 25 °C): δ = 31.61 (CH3), 34.72 (CCH3), 52.29 (OCH3),

118.56, 120.83, 121.13, 123.21, 123.37, 127.46, 128.81, 130.87 (meso-C, Bn),

EXPERIMENTAL PART

113

131.70, 131.81, 132.01 (pyrrole), 134.49, 134.72, 140.42 (Bn), 149.91, 150.12,

150.21 (pyrrole), 150.34 (Bn), 167.68 (C=O) ppm.

EA: calc. (%) for C58H54N4O2Zn x 0.5 H2O (904.46) = C 75.52, H 6.12, O 5.20, N

6.07, Zn 7.09; found: C 75.12, H 6.05, N 5.85.

MS (FAB): m/z = 903 [M]+.

UV/Vis (CH2Cl2): [λ/nm] (ε/lmol-1cm-1) 421.5 (564600), 549.5 (23100), 587.0 (6400).

IR (ATR): νmax = 2970, 2360, 2342, 1737, 1727, 1608, 1491, 1458, 1435, 1396,

1365, 1274, 1229, 1217, 1206, 1111, 1068, 998, 811, 797, 768, 720 cm-1.

Synthesis of Zinc-5,15-bis[4-(methoxycarbonyl)phenyl]-10,20-bis(tert-butylphenyl)-porphyrin 80:




stirred at RT for 12 h. The solution was concentrated

to dryness and purified by column chromatography

(SiO2, CH2Cl2→CH2Cl2/EtOAc 50:1, Rf = 0.51). Yield: 154.8 mg (96 %), pink powder.


(d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.11 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.30 (d, 3JH,H = 8.4 Hz, 4

H, Bn), 8.40 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.81 (d, 3JH,H = 4.4 Hz, 4 H, pyrrole), 8.93 (d, 3JH,H = 4.4 Hz) ppm. 13C NMR (100.5 MHz, CDCl3, 25 °C): δ = 31.63 (CH3), 34.76 (CCH3), 52.28 (OCH3),

119.2, 121.18, 123.31, 127.51, 128.95 (meso-C, Bn), 131.15, 132.19 (pyrrole),

134.47, 134.72, 140.26, 148.62 (10 C, Bn), 149.40 (pyrrole), 150.07 (Bn), 150.40

(pyrrole), 167.80 (C=O) ppm.

MS (FAB): m/z = 904 [M]+.

UV/Vis (THF): [λ/nm] (ε/lmol-1cm-1) 426.0 (591800), 557.0 (23400), 598.5 (9900).

IR (ATR): νmax = 3003, 2970, 2359, 2341, 1737, 1606, 1524, 1437, 1365, 1312, 1270,

1228, 1217, 1206, 1112, 1099, 1072, 997, 814, 795, 764, 717 cm-1.

EXPERIMENTAL PART

114

Synthesis of Zinc-5,10-bis[4-(methoxycarbonyl)phenyl]-15,20-bis(tert-butylphenyl)-porphyrin 81:




stirred at RT for 12 h. The solution was


chromatography (SiO2, CH2Cl2/EtOAc 95:5, Rf =

0.62).

Yield: 96.3 mg (90 %) pink powder.


(d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.10 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.29 (d, 3JH,H = 7.8 Hz, 4

H, Bn), 8.39 (d, 3JH,H = 7.8 Hz, 4 H, Bn), 8.81 (m, 4 H, pyrrole), 8.91 (m, 4 H, pyrrole)

ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 31.66 (CH3), 34.78 (CCH3), 52.28 (OCH3),

122.68, 123.18, 127.43, 128.80, 130.95 (meso-C, Bn), 131.26, 131.88, 132.19

(pyrrole), 134.31, 134.47, 148.29 (Bn), 148.74, 148.76, 149.93 (pyrrole), 167.46

(C=O) ppm.

EA: calc. (%) for C56H48N4O4Zn x H2O (904.30) = C 73.48, H 5.40, O 7.87, N 6.12,

Zn 7.14; found: C 73.51, H 5.33, N 5.94.

MS (FAB): m/z = 905 [M+H]+.


IR (ATR): νmax = 3005, 2970, 1360, 2342, 1738, 1608, 1542, 1524, 1456, 1435, 1366,

1274, 1229, 1217, 1206, 1109, 999, 815, 797, 765, 720 cm-1.

EXPERIMENTAL PART

115

Synthesis of Zinc-5,10-bis(tert-butylphenyl)-15,20-bis(4-ethynylphenyl)-porphyrin 82:



μmol) in 20 mL THF and the reaction mixture was

heated at reflux for 1 h. The solvent was

evaporated under vacuum and the remaining

residue was dissolved in 20 mL of CH2Cl2. The

organic phase was washed two times with 20 mL

water and dried over Na2SO4, filtrated and

concentrated to dryness.

Yield 42.00 mg (100 %), pink powder.

1H NMR (300 MHz, CDCl3, 25ºC): δ = 1.58 (s, 18 H, CH3), 3.32 (s, 2 H, C≡CH), 7.76

(d, 3JH,H = 8.1 Hz, 4 H, Bn), 7.89 (d, 3JH,H = 8.1 Hz, 4 H, Bn), 8.16 (m, 8 H, Bn), 8.83

(m, 4 H, pyrrole), 8.91 (m, 4 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25ºC): δ = 30.12 (CH3), 35.31 (CCH3), 78.55, 84.19

(C≡C), 120.23, 121.70, 121.99, 122.18, 123.91, 130.79, 131.89, 132.15, 132.66,

132.90 (pyrrole, Bn, meso-C), 134.70, 140.03, 143.98 (Bn), 150.14, 150.22 (pyrrole),

150.76 (Bn), 150.79, 150.87 (pyrrole) ppm.

MS (FAB): m/z = 836 [M]+.


591.0 (3900), 647.0 (3200).

IR (ATR): νmax = 2969, 2924, 2854, 2360, 2342, 1738, 1542, 1456, 1366, 1260,

1229, 1217, 1089, 1016, 865, 796 cm-1.

EXPERIMENTAL PART

116

Synthesis of Zinc-5-tert-butylphenyl-10,15,20-tris(4-ethynylphenyl)-porphyrin 83:



μmol) in THF (20 mL). The reaction mixture was

heated at reflux for 1 h. The solution was

evaporated to dryness and the remaining residue

was dissolved in 20 mL of CH2Cl2 and washed two

times with 20 mL water. The organic layer was

dried over Na2SO4, filtrated and concentrated to

dryness.

Yield: 22.00 mg (100 %) pink powder. 1H NMR (300 MHz, CDCl3, 25 ºC): δ = 1.62 (s, 9 H, CH3), 3.32 (s, 3 H, C≡CH), 7.75

(d, 3JH,H = 8.1 Hz, 2 H, Bn), 7.88 (d, 3JH,H = 8.1 Hz, 6 H, Bn), 8.15 (d, 8 H, Bn), 8.92

(m, 6 H, pyrrole), 9.01 (d, 3JH,H = 4.8 Hz, 2 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 ºC): δ = 29.96 (CH3), 31.69 (CCH3), 78.19, 83.71

(C≡C), 120.06, 120.24, 121.38, 122.01, 123.54, 130.39 (Bn, meso-C), 131.67,

131.93, 132.62 (pyrrole), 134.23, 134.32, 139.42, 143.38, 149.75, 149.83 (Bn),

149.89, 150.45, 150.56 (pyrrole) ppm.

MS (FAB): m/z = 804 [M]+.


591.0 (7600), 647.0 (6900).

IR (ATR): νmax = 2970, 2924, 2854, 2360, 2342, 1738, 1541, 1456, 1366, 1260,

1229, 1217, 1091, 1017, 857, 796, 721 cm-1.

EXPERIMENTAL PART

117

Synthesis of Zinc-5,10-bis(3,5-dimethoxyphenyl)-15,20-bis{4-[2-(trimethylsilyl) ethynyl]phenyl}porphyrin 85:

Zn(OAc)2 dihydrate (72.00 mg, 330.00 µmol) was

added to a solution of 71 (60.00 mg, 66.60 µmol)

in 15 mL THF. The reaction was mixture was

heated at reflux for 90 min. The solution was


chromatography (SiO2, CH2Cl2, Rf = 0.85).

Yield: 79.00 mg (81 %), pink powder.

1H NMR (300 MHz, CDCl3, 25 °C): δ = 0.39 (s, 18 H, SiCH3), 3.91 (s, 12 H, OCH3),

6.84 (t, 3JH,H = 2.1 Hz, 2 H, Bn), 7.36 (d, 3JH,H = 2.4 Hz, 4 H, Bn), 7.87 (d, 3JH,H = 8.1

Hz, 4 H, Bn), 8.16 (d, 3JH,H = 7.8 Hz, 4 H, Bn), 8.87 (m, 4 H, pyrrole), 9.00 (m, 4 H,

pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 0.07 (SiCH3), 55.58 (OCH3), 95.38 (C≡C),

99.97 (Bn), 105.07 (C≡C), 113.69, 120.30, 120.96, 122.31, 130.21 (Bn, meso-C),

131.70, 131.79, 132.10, 132.20 (pyrrole), 134.24, 143.09, 144.53 (Bn), 149.75,

149.86, 149.98, 150.09 (pyrrole), 158.64 (Bn) ppm.

EA: calc. (%) for C58H52N4O4Si2Zn x 0.25 CH2Cl2 (990.62) = C 69.14, H 5.23, N 5.54;

found: C 69.17, H, 5.56, N, 5.08.

MS (FAB): m/z = 990 [M]+.


IR (ATR): νmax = 3002, 2970, 2360, 2342, 2157, 1739, 1592, 1524, 1494, 1455,

1421, 1366, 1350, 1249, 1228, 1217, 1204, 1154, 1065, 1001, 950, 932, 859, 843,

811, 797, 760, 719 cm-1.

EXPERIMENTAL PART

118

Synthesis of Zinc-10,20-bis(2,4,6-trimethoxyphenyl)-5,15-bis{4-[2-(trimethylsilyl)ethynyl]phenyl}porphyrin 86:

Zn(OAc)2 dihydrate (77.90 mg, 355.00

μmol) was added to a suspension of 75

(70.00 mg, 71.00 μmol) in 20 mL THF.

The reaction mixture was heated at reflux.

After 10 min the solid had entirely

dissolved and the reaction was heated at

reflux for further 40 min. The solution was

concentrated to dryness and purified by

column chromatography (SiO2, CH2Cl2, Rf = 0.32).

Yield: 73.00 mg (98%), pink powder. 1H NMR (400 MHz, CDCl3, 25ºC): δ = 0.40 (s, 18 H, SiCH3), 3.51 (s, 12 H, OCH3),

4.08 (s, 6 H, OCH3), 6.58 (s, 4 H, Bn), 7.85 (d, 3JH,H = 7.5 Hz, 4 H, Bn), 8.16 (d, 3JH,H = 7.9 Hz, 4 H, Bn), 8.84 (d, 3JH,H = 4.1 Hz, 4 H, pyrrole), 8.92 (d, 3JH,H = 4.1 Hz,

4 H, pyrrole) ppm. 13C NMR (100.5 MHz, CDCl3, 25ºC): δ = 0.39 (SiCH3), 55.59, 56.10 (OCH3), 90.90

(Bn), 95.00, 105.35 (C≡C), 112.97, 113.27, 119.05, 121.87, 130.02 (Bn, meso-C),

131.15, 131.55 (pyrrole), 134.29, 143.69 (Bn), 149.46, 150.94 (pyrrole), 160.99,

161.67 (Bn) ppm.

EA: calc. (%) for C60H56N4O6Si2Zn x 2 H2O (1050.67) = C 66.31, H 5.57, N 5.16, O

11.78, Si 5.17, Zn 6.02; found: C 66.96, H 5.55, N 5.02.

MS (FAB): m/z = 1050 [M]+.


IR (ATR): νmax = 3002, 2970, 2361, 2341, 2155, 1738, 1648, 1636, 1606, 1585,

1558, 1541, 1523, 1507, 1490, 1456, 1435, 1411, 1365, 1338, 1250, 1218, 1204,

1153, 1124, 1067, 1036, 999, 951, 859, 842, 812, 796, 760, 719 cm-1.

EXPERIMENTAL PART

119

Synthesis of Zinc-10,20-Bis[4-tert-butyl-2,6-(methoxymethyl)phenyl]-5,15-{4-[2-(trimethylsilyl)ethynyl]phenyl}porphyrin 87

Zn(OAc)2 dihydrate (200.00 mg, 0.91

mmol) was suspended in 2 mL of MeOH

and added to a solution of 78 (200.00 mg,

0.18 mmol) in 60 mL THF. The reaction

mixture was heated at reflux for 12 h. The

solution was concentrated to dryness and

purified by column chromatography (SiO2,

CH2Cl2/ EtOAc 9:1).

Yield: 175.00 mg (83 %), pink powder. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 0.38 (s, 18 H, SiCH3), 1.64 (s, 18 H, CH3),

2.71 (s, 12 H, OCH3), 3.88 (s, 8 H, CH2), 7.84 (d, 3JH,H = 8.4 Hz, 8 H, Bn), 8.17 (d, 3JH,H = 8.0 Hz, 4 H, Bn), 8.66 (d, 3JH,H = 4.8 Hz, 4 H, pyrrole), 8.76 (d, 3JH,H = 4.8 Hz, 4

H, pyrrole) ppm. 13C NMR (100.5 MHz, CDCl3, 25 °C): δ = 0.50 (SiCH3), 32.16 (CH3), 35.59 (CCH3),

58.33 (OCH3), 73.52 (CH2), 95.58, 105.68 (C≡C) 115.90, 119.81, 122.29, 122.49,

130.41 (Bn), 130.41, 131.32 (meso-C, pyrrole), 132.28, 134.97, 136.83, 139.71,

144.07 (Bn), 150.16, 150.23 (pyrrole), 151.77 (Bn) ppm.

EA: calc. (%) for C70H76N4O4Si2Zn x 0.5 H2O (1156.47) = C 71.30, H 6.26, N 5.04, O

6.48, Zn 5.88; found C 71.60, H 6.55, N 5.32.

MS (FAB): m/z = 1158 [M+H]+.


IR (ATR): νmax = 2970, 2360, 2157, 1738, 1460, 1365, 1248, 1228, 1217, 1203,

1115, 996, 967, 858, 843, 797, 758, 721 cm-1.

EXPERIMENTAL PART

120

Synthesis of Zinc-5-[4-(hydroxycarbonyl)phenyl]-5,10,15-tris(tert-butylphenyl)-porphyrin 88:

Two pellets of KOH were added to a solution of 79

(53.00 mg, 58.47 µmol) in 25 mL of EtOH. The

reaction mixture was heated at reflux for 12 h. The

solution was concentrated to dryness, the residue

was dissolved in 30 mL of CHCl3 and extracted

three times with 20 mL of a saturated aqueous

solution of NH4Cl. The organic layer was separated,

washed three times with 20 mL of water and dried

over MgSO4. The solution was filtrated and


Yield: 51.70 mg (99 %), pink powder. 1H NMR (400 MHz, DMSO-d6, 25 °C): δ = 1.55 (s, 27 H, CH3), 7.78 (d, 3JH,H = 7.6 Hz,

6 H, Bn), 8.07 (d, 3JH,H = 7.6 Hz, 6 H, Bn), 8.29 (d, 3JH,H = 8.4 Hz, 2 H, Bn), 8.34 (d, 3JH,H = 8.4 Hz, 2 H, Bn), 8.78 (m, 8 H, pyrrole) ppm. 13C NMR (100.5 MHz, DMSO-d6, 25 °C): δ = 31.46 (CH3), 34.61 (CCH3), 118.95,

120.45, 120.63, 123.41, 127.51, 128.81, 130.87, 131.23 (meso-C, Bn), 131.61,

131.89 (pyrrole), 134.10, 134.31, 139.77, 148.77, 149.41 (Bn), 149.49, 149.62

(pyrrole), 170.68 (C=O) ppm.

EA: calc. (%) for C57H52N4O2Zn (904.46) x 6 H2O = C 68.56, H 6.46, O 12.82, N 5.61,

Zn 6.55; found: C 68.67, H 6.77, N 5.00.

MS (FAB): m/z = 904 [M]+.


IR (ATR): νmax = 2970, 2360, 2342, 1738, 1608, 1541, 1524, 1508, 1489, 1457,

1436, 1365, 1271, 1229, 1217, 1206, 1110, 1072, 1000, 854, 813, 797, 769, 720

cm-1.

EXPERIMENTAL PART

121

Zinc 5,15-bis[4-(hydroxycarbonyl)phenyl]-10,20-bis(tert-butylphenyl)-porphyrin 89:





was suspended in 30 mL of a saturated aqueous

solution of NH4Cl and stirred for 30 min. The

solution was filtrated and the filtrate was washed

with water (3 x 20 mL). Yield: 46.50 mg (94 %),

pink powder. 1H NMR (400 MHz, DMSO-d6, 25 °C): δ = 1.55 (br, 18 H, CH3), 7.80 (br, 4 H, Bn),

8.10 (br, 4 H, Bn), 8.28 (br, 4 H, Bn), 8.35 (br, 4 H, Bn), 8.78 (br, 8 H, pyrrole) ppm. 13C NMR (100.5 MHz, DMSO-d6, 25 °C): δ = 31.47 (CH3), 34.63 (CCH3), 119.33,

120.65, 123.46, 127.51, 130.47 (meso-C, Bn), 131.42, 131.99 (pyrrole), 134.13,

134.34, 139.68 (Bn), 147.09 (pyrrole), 148.80, 149.55 (Bn), 149.70 (pyrrole), 167.76

(C=O) ppm.

EA: calc. (%) for C54H44N4O4Zn (878.34) = C 58.30, H 6.34, O 24.45, N 5.04 Zn 5.88;

found: C 58.46, H 4.27, N 4.88.

MS (FAB): m/z = 878 [M]+.


IR (ATR): νmax = 3016, 2970, 2360, 2342, 1738, 1541, 1457, 1435, 1366, 1229,

1217, 1206, 999, 796, 769, 719 cm-1.

EXPERIMENTAL PART

122

Synthesis of 5,10-bis[4-(hydroxycarbonyl)phenyl]-5,10-bis(tert-butylphenyl)-porphyrin 90:





was dissolved in 30 mL saturated aqeous solution

of NH4Cl and stirred for 30 min. The solution was

filtrated and the filtrate was washed water (3 x 20

mL).

Yield: 88.00 mg (83 %), pink powder. 1H NMR (400 MHz, DMSO-d6, 25 °C): δ = 1.57 (s, 18 H, CH3), 7.81 (d, 3JH,H = 7.6 Hz,

4 H, Bn), 8.10 (d, 3JH,H = 8.0 Hz, 4 H, Bn), 8.22 (d, 3JH,H = 7.2 Hz, 4 H, Bn), 8.32 (d, 4

H, Bn), 8.80 (m, 8 H, pyrrole) ppm. 13C NMR (100.5 MHz, DMSO-d6, 25 °C): δ = 31.46 (CH3), 34.61 (CCH3), 119.77,

120.55, 123.43, 127.33, 131.38 (meso-C, Bn), 131.63, 131.83, 133.90 (pyrrole),

134.11, 134.51, 139.80 (Bn), 149.04 149.42, 149.62 (pyrrole), 168.27 (C=O) ppm

EA: calc. (%) for C54H44N4O4Zn (878.34) x 5 H2O= C 66.97, H 5.62, O 14.87, N 5.79,

Zn 6.75; found: C 67.16, H 5.14, N 5.64.

MS (FAB): m/z = 878 [M]+.


IR (ATR): νmax = 3004, 2970, 2360, 2342, 1738, 1606, 1541, 1523, 1456, 1436,

1366, 1271, 1229, 1217, 1206, 1110, 998, 796, 720 cm-1.

EXPERIMENTAL PART

123

Synthesis of Nickel-10,20-bis[4-tert-butyl-2,6-(methoxymethyl)phenyl]-5,15-bis{4-[2-(trimethylsilyl)ethynyl]phenyl}-porphyrin 91

Nickel (II) acetylacetonate (29.31 mg,

114.10 µmol) was added to a solution of

porphyrin 78 (25.00 mg, 22.82 µmol) in

20.0 mL of toluene. The reaction mixture

was heated at reflux for 12 h. The solution

was concentrated to dryness and purified

by column chromatography (SiO2,

CH2Cl2/hexane 8:2; Rf = 0.46) Yield: 21.0

mg (80 %), cherry red powder. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 0.37 (s, 18 H, SiCH3), 1.61 (s, 18 H, CH3),

2.86 (s, 12 H, OCH3), 3.90 (s, 8 H, CH2), 7.83 (d, 3JH,H = 8.4 Hz, 8 H, Bn), 8.02 (d, 3JH,H = 8.4 Hz, 4 H, Bn), 8.61 (d, 3JH,H = 5.2 Hz, 4 H, pyrrole), 8.70 (d, 3JH,H = 5.2 Hz, 4

H, pyrrole) ppm. 13C NMR (100.5 MHz, CDCl3, 25 °C): δ = 0.46 (SiCH3), 32.09 (CH3), 35.60 (CCH3),

58.58 (OCH3), 73.29 (CH2), 96.00, 105.30 (C≡C), 115.07, 118.72, 122.93, 123.12,

130.95 (Bn, meso-C), 132.14, 123.69 (pyrrole), 134.03, 134.30, 139.53, 141.54,

143.16, 143.17, 152.40 (pyrrole, Bn) ppm.

MS (MALDI TOF, dctb): m/z = 1150 [M]+. EA: calc. (%) for C70H76N4NiO4Si2 x 1,5 CH2Cl2 (1152.24) = C 67.11, H 6.22, Cl 8.31,

N 4.38, Ni 4.59, O 5.00, Si 4.39; found: C 66.69, H 6.19, N 4.15.

UV/Vis (CH2Cl2): [λ/nm] (ε/lmol-1cm-1) 417.0 (264200), 528.0 (20900).

IR (ATR): νmax = 2961, 2924, 2822, 2159, 1605, 1499, 1393, 1351, 1290, 1250,

1220, 1194, 1102, 1003, 952, 930, 863, 843, 815, 803, 761, 716 cm-1.

EXPERIMENTAL PART

124

Synthesis of the four-fold Hamilton receptor functionalized porphyrin 93:

EDC (407.00 mg, 2.13 mmol) and DMAP (260.00 mg, 2.13 mmol) were added to a

solution of compound 45 (957.00 mg, 1.88 mmol) and 5,10,15,20-tetrakis-[4-

(hydroxycarbonyl)phenyl]porphyrin 92 (300.00 mg, 0.38 mmol) in 8 mL of dry DMF at

RT. The reaction was allowed to proceed for 7 d in the dark and the crude reaction

product was precipitated with water. The precipitate was collected by filtration,

washed three times with 20 mL of water and air dried overnight. The reaction product

was dried under reduced pressure at 50 °C for one day and purified by repeated

column chromatography (SiO2, THF, THF/CH2Cl2 80:20; Rf = 0.95) followed by

preparative HPLC (Nucleosil, THF/CH2Cl2 80:20).

Yield: 52 mg (5 %), purple solid. 1H NMR (400 MHz, DMF-d7, 25 °C): δ = -2.69 (br, 2 H, NH), 0.96 (t, 3JH,H = 7.3 Hz,

24 H, CH3), 2.74 (m, 16 H, CH2), 2.78 (t, 3JH,H = 7.4 Hz, 16 H, CH2) 7.94 (dd, 8 H,

Py), 8.02 (m, 16 H, Py) , 8.50 (d, 4JH,H = 0.8 Hz, 8 H, Bn), 8.67 (d, 3JH,H = 8.1 Hz, 8 H,

EXPERIMENTAL PART

125

Bn), 8.77 (d, 3JH,H = 8.3 Hz, 8 H, Bn), 8.84 (s, 8 H, Bn), 9.11 (s, 8 H, pyrrole β-H),

10.39 (br, 8 H, CONH), 10.92 (br, 8 H, CONH). 13C NMR (100.5 MHz, DMF-d7, 25 °C): δ = 13.93 (CH3), 19.4, 39.1 (CH2), 110.4 (Py),

120.2, 125.8, 126.1, 129.5, 135.8, 137.2, 140.7, 151.5, 152.0 (Bn, Py, meso-C),

163.0, 165.7, 173.0 (C=O) ppm. MS (FAB): m/z = 2736 [M] +.

IR (ATR): νmax = 1671, 1584, 1293, 1241, 1177, 1067, 797, 729 cm-1.

UV/Vis (THF): [λ/nm] (ε/lmol-1cm-1) = 301.0 (142000), 420.0 (429000), 515.0 (19600),

547.0 (9320), 590.0 (6150).

Synthesis of Zinc -5,10-bis(3,5-dimethoxyphenyl)-15,20-bis(4-ethynylphenyl) porphyrin 98:

A solution of TBAF in THF (1 M, 0.40 mL) was added

dropwise to a solution of compound 85 (66.00 mg,

68.40 µmol) in 5 mL of dry THF. The reaction mixture

was stirred under inert conditions at RT for 12 h. The

solution was evaporated to dryness, the residue was

dissolved in 15 mL CH2Cl2 and extracted two times

with 10 mL of aqueous solution of NaHCO3 (5 %). The

organic layer was separated, washed two times with 10

mL of water and dried over Na2SO4. The solution was filtrated, concentrated to

dryness and purified by column chromatography (SiO2, CH2Cl2, Rf = 0.66).

Yield: 62.00 mg (93 %) pink powder. 1H NMR (300 MHz, CDCl3, 25 °C): δ = 3.32 (s, 2 H, C≡H), 3.91 (s, 12 H, OCH3), 6.85

(br, 2 H, Bn), 7.37 (d, 3JH,H = 2.1 Hz, 4 H, Bn), 7.88 (d, 3JH,H = 8.1 Hz, 4 H, Bn), 8.18

(d, 3JH,H = 8.1 Hz, 4 H, Bn), 8.92 (m, 4 H, pyrrole), 9.03 (m, 4 H, pyrrole) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 55.58 (OCH3), 87.16 (C≡CH), 83.72 (C≡C),

99.95, 113.73, 120.09, 120.98, 121.32, 130.36 (Bn, meso-C), 131.68, 131.77,

132.11, 132.21 (pyrrole), 134.31, 143.47, 144.55 (Bn), 149.70, 149.83, 149.97,

150.11 (pyrrole), 158.62 (Bn) ppm.

EA: calc. (%) for C52H36N4O4Zn (846.26) = C 73.80, H 4.29, N 6.62, O 7.56, Zn 7.73;

found: C 74.89 H, 5.95; N, 5.51.

MS (FAB): m/z = 844 [M]+.

EXPERIMENTAL PART

126


IR (ATR): νmax = 3287, 3004, 2970, 2360, 2341, 1738, 1591, 1525, 1494, 1455,

1421, 1366, 1348, 1229, 1216, 1203, 1154, 1065, 1001, 950, 933, 858, 811, 797,

767, 745, 719 cm-1.

Synthesis of the Hamilton receptor functionalized Zinc-porphyrin 99:

Compound 48 (73.60 mg, 110.00 µmol)

was dissolved in 12 mL dry THF/NEt3

(2:1). Pd2(dba)3 (77.00 mg,

84.10 µmol), AsPh3 (129.00 mg, 421.00

µmol) and 98 (30.00 mg, 36.60 µmol)

were added and the reaction was

allowed to proceed for 6 d in the dark

under inert conditions. The solution was

concentrated to dryness and purified by

repeated column chromatography

(SiO2, CH2Cl2 → CH2Cl2/EtOAc 1:1,

CH2Cl2/MeOH 99:1 → 98:2, Rf = 0.18)

and recrystallized from CH2Cl2/pentane.

Yield: 27.00 mg (38 %), dark violet powder. 1H NMR (400 MHz, THF-d8, 25 °C): δ = 1.10 (s, 36 H, CH3), 2.58 (s, 8 H, CH2), 3.95

(s, 12 H, OCH3), 6.93 (t, 3JH,H = 2.1 Hz, 2 H, Bn), 7.39 (d, 3JH,H = 2.4 Hz, 4 H, Bn),

7.76 (dd, 3JH,H = 8.1 Hz, 4 H, Py), 8.07 (m, 12 H, Bn, Py), 8.30 (d, 3JH,H = 8.1 Hz, 4 H,

Py), 8.45 (d, 3JH,H = 1.8 Hz, 4 H, Bn), 8.55 (br, 2 H, Bn), 8.88 – 9.01 (m, 8 H, pyrrole),

9.08 (br, 4 H, NH), 9.77 (br, 4 H, NH) ppm. 13C NMR (100.5 MHz, THF-d8, 25 °C): δ = 29.99 (CH3), 31.64 (CCH3), 50.71 (CH2),

55.62 (OCH3), 89.47, 91.67 (C≡C), 98.63, 100.14 (Bn), 110.21, 110.42 (Py), 114.65,

120.30, 121.73, 122.55, 124.96, 127.53, 130.48 (Bn, meso-C), 131.93, 132.38

(pyrrole), 134.29, 135.52, 136.80, 140.57, 145.29, 145.87 (Bn), 150.36, 150.60,

150.82, 151.01 (pyrrole), 151.23, 151.76, 159.86 (Bn), 164.88, 170.75 (C=O) ppm.

EA: calc. (%) for C112H104N16O12Zn x 1.5 CH2Cl2 (1931.51) = C 66.21, H 5.24, Cl

5.17, N 10.86, O 9.32, Zn 3.18; found C 66.44, H 4.80, N 10.32.

MS (FAB): m/z = 1932 [M]+.

EXPERIMENTAL PART

127


(26500), 589.0 (6400).

IR (ATR): νmax = 3003, 2970, 2360, 2341, 1738, 1586, 1522, 1507, 1446, 1366,

1352, 1298, 1229, 1217, 1204, 1154, 1066, 999, 950, 904, 858, 797, 752, 719 cm-1.

Synthesis of Zinc-10,20-bis(2,4,6-trimethoxyphenyl)-5,15-bis(4-ethynylphenyl) porphyrin 100:

A solution of TBAF in THF (1 M, 1.87 mL) was

added dropwise to a solution of compound 86

(329.00 mg, 312.00 μmol) in 25 mL of dry THF. The

resulting suspension was stirred under inert

conditions at RT for 150 min. The reaction mixture

was diluted with 30 mL of EtOAc and extracted two

times with 30 mL aqueous solution of NaHCO3

(5 %). The organic layer was separated, washed

two times with 20 mL water and dried over Na2SO4. The solution was filtrated and

concentrated to dryness. Due to sufficient purity (verified by NMR analysis), 100 was

used without further purification.

Yield: 486.00 mg (100 %). 1H NMR (400 MHz, CDCl3, 25ºC): δ = 3.30 (s, 2 H, C≡CH), 3.49 (s, 12 H, OCH3),

4.09 (s, 6 H, OCH3), 6.59 (s, 4 H, Bn), 7.84 (d, 3JH,H = 8 Hz, 4 H, Bn), 8.17 (d, 3JH,H =

8.4 Hz, 4 H, Bn), 8.84 (d, 3JH,H = 4.4 Hz, 4 H, pyrrole), 8.91 (d, 3J = 4.8 Hz, 4 H,

pyrrole) ppm. 13C NMR (100.5 MHz, CDCl3, 25ºC): δ = 55.59, 56.11 (OCH3), 77.86, 83.95 (C≡C),

90.91, 112.99, 113.27, 118.91, 120.92, 130.17 (Bn, meso-C), 131.19, 131.56

(pyrrole), 134.32, 144.02 (Bn), 149.45, 150.98 (pyrrole), 161.02, 161.67 (Bn) ppm.

EA: calc. (%) for C54H40N4O6Zn x 1.5 H2O (906.31) = C 69.49, H 4.64, N 6.00, O

12.86, Zn 7.01; found: C 69.34, H 4.76, N 5.59.

MS (FAB): m/z = 904 [M]+.

UV/Vis (CH2Cl2): [λ/nm] (ε/lmol-1cm-1) 428 (446500), 556 (18900), 598 (4000).

IR (ATR): νmax = 2970, 2360, 2341, 1738, 1606, 1457, 1436, 1366, 1227, 1217,

1205, 1150, 1123, 998, 808, 798 cm-1.

EXPERIMENTAL PART

128

Synthesis of the cyanuric acid functionalized Zinc-porphyrin 102:

Compound 101 (47.40 mg,

143.00 μmol) was first

dissolved in 5 mL of dry THF

and then 10 mL of dry

CH2Cl2/NEt3 (1:1), Pd2(dba)3

(116.30 mg, 127.00 μmol),

AsPh3 (197.40 mg, 645.00

μmol) and 100 (50.00 mg, 55.00 μmol) were added. The reaction was allowed to

proceed for 7 d in the dark under inert conditions. The solution was concentrated to

dryness and subjected to column chromatography (SiO2, EtOAc → THF →

THF/acetic acid 9:1). After column chromatography, the product was only soluble in a

few polar solvents like DMSO, pyridine and DMF which made further purification via

common methods impossible.

MS (FAB): m/z = 1312 [M]+.


Compound 48

(65.30 mg, 973.00

μmol) was first

dissolved in 5 mL

of dry THF and

then 12 mL of dry

CH2Cl2/NEt3 (1:1),

Pd2(dba)3 (86.00 mg, 946.00 μmol), AsPh3 (145.00 mg, 473.00 μmol) and 100 (50.00

mg, 55.00 μmol) were added. The reaction was allowed to proceed for 5 d in the dark

and under inert conditions. The solution was concentrated to dryness and purified by

column chromatography (SiO2, CHCl3 → CHCl3/ AcOH 98:2 → CHCl3/ AcOH 95:5 →

THF). The target molecule fractions were evaporated to dryness, dissolved in 30 mL

CH2Cl2 and stirred vigorously with 30 mL half saturated aqueous solution of NaHCO3

to remove the remaining AcOH. After 30 minutes the phases were separated and the

EXPERIMENTAL PART

129

organic phase was washed three times with 20 mL water. The organic phase was

dried over Na2SO4, filtrated and concentrated to dryness.

Yield 30.00 mg (37 %) dark red powder. 1H NMR (400 MHz, THF-d8, 25 ºC): δ = 1.10 (br, 36 H, CH3), 2.30 (br, 8 H, CH2),

3.47 (12 H, OCH3), 4.08 (br, 6 H, OCH3), 6.67 (br, 4 H, Bn), 7.38-10.06 (44 H, Bn,

pyrrole, NH) ppm. 13C NMR (100.5 MHz, THF-d8, 25 ºC): δ = 31.62 (CH3), 32.75 (CCH3), 50.67 (CH2),

55.59, 55.82 (OCH3), 91.33 (Bn), 92.13 (C≡C), 110.05, 110.22, 110.34, 129.22,

129.89, 130.18, 130.42, 131.24, 131.69, 132.16, 132.57, 132.97, 135.00, 135.40,

136.61, 140.48 (meso-C, Bn, Py, pyrrole), 151.06, 151.31, 151.79, 151.93 (Py,

pyrrole), 161.99, 162.90 (Bn), 164. 90, 171.01 (C=O) ppm.

MS (FAB): m/z = 1990 [M]+.

UV/Vis (CH2Cl2): [λ/nm] (ε/lmol-1cm-1) 303.0 (68300), 425.0 (147000), 551.0 (10400)

594.0 (2200). Synthesis of Zinc-10,20-bis[4-tert-butyl-2,6-(methoxymethyl)phenyl]-5,15-bis(4-ethynylphenyl)porphyrin 104:


added dropwise to a solution of 87 in 10 mL of dry

THF. The reaction mixture was stirred under inert

conditions at RT for 12 h. The solution was

evaporated to dryness and the residue was

dissolved in 30 mL of CH2Cl2 and extracted two

times with 30 mL aqueous solution of NaHCO3

(5 %). The organic layer was separated, washed

two times with 30 mL water and dried over Na2SO4.

The solution was filtrated, concentrated to dryness and purified by column

chromatography (SiO2, CH2Cl2/EtOAc 97:3, Rf = 0.52).

Yield: 115.00 mg (79 %), pink powder. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 1.63 (s, 18 H, CH3), 2.71 (s, 12 H, OCH3),

3.33 (s, 2 H, C≡H), 3.88 (8 H, CH2), 7.84 (8 H, Bn), 8.17 (d, 3JH,H = 8.0 Hz, 4 H, Bn),

8.67 (d, 3JH,H = 4.4 Hz, 4 H, pyrrole), 8.77 (d, 3JH,H = 4.4 Hz, 4 H, pyrrole) ppm.

EXPERIMENTAL PART

130

13C NMR (100.5 MHz, CDCl3, 25 °C): δ = 32.16 (CH3), 35.59 (CCH3), 58.31 (OCH3),

73.52 (CH2), 78.47 (C≡C), 84.30 (C≡CH), 115.96, 119.69, 121.37, 122.52, 130.56

(Bn, meso-C), 131.37, 132.30 (pyrrole), 135.01, 136.10, 136.84, 139.72, 144.36 (Bn),

150.13, 150.27 (pyrrole), 151.80 (Bn) ppm.

MS (FAB): m/z = 1014 [M]+.

EA: calc. (%) for C64H60N4O4Zn x 0.5 H2O (1014.58) = C 74.49, H 5.52, N 5.79, O

7.44, Zn 6.76; found C 74.08, H 5.88, N 5.16.


IR (ATR): νmax = 3003, 2970, 2360, 2341, 1738, 1456, 1365, 1229, 1217, 1205,

1102, 1065, 998, 908, 809, 797, 720 cm-1.

Synthesis of the cyanuric acid functionalized Zinc-porphyrin 105:

Pd2(dba)3 (103.80 mg,

113.36 µmol), AsPh3 (137.00

mg, 447.38 µmol) and 104

(50.00 mg, 492.82 µmol)

were added to a solution of

101 (39.10 mg, 118.01 µmol)

dissolved in 17.4 mL of a

mixture of THF/NEt3 (2:1).

The reaction was allowed to proceed in the dark and under inert conditions for 6 d.

The reaction mixture was concentrated to dryness and subjected to column

chromatography (SiO2, CH2Cl2 → CH2Cl2/MeOH 99:1 → 9:1→ THF→ THF/MeOH

9:1).

MS (MALDI TOF, dctb): m/z = 1419 [M]+.

EXPERIMENTAL PART

131


48 (87.20 mg,

130.04 µmol) was

dissolved in 17.5

mL of a mixture of

dry THF/NEt3 (2:1).

Pd2(dba)3 (114.20

mg, 124.71 µmol),

AsPh3 (191.40 mg,

625.02 µmol) and 104 (55.00 mg, 542.10 µmol) were added and the reaction was

allowed to proceed for 6 d in the dark under inert conditions. The solution was

concentrated to dryness and purified by repeated column chromatography (SiO2,

CH2Cl2 → CH2Cl2/MeOH 99:1 → CH2Cl2/MeOH 98:2 → CH2Cl2/MeOH 98:2.5).

Yield: 35.00 mg (31 %), violet powder. 1H NMR (400 MHz, THF-d8, 25 °C): δ = 1.10 (s, 36 H, CH3), 1.65 (s, 18 H, CH3), 2.29

(s, 8 H, CH2), 2.78 (s, 12 H, OCH3), 3.95 (s, 8 H, CH2), 7.77 (dd, 3JH,H = 8.0 Hz, 4 H,

Py), 7.94 (s, 4 H, Bn), 8.06 (m, 12 H, Bn, Py), 8.29 (d, 3JH,H = 7.9 Hz, 4 H, Bn), 8.45

(s, 4 H, Bn), 8.57 (s, 2 H, Bn), 8.69 (d, 3JH,H = 4.5 Hz, 4 H, pyrrole), 8.84 (d, 3JH,H =

4.5 Hz, 4 H, pyrrole), 9.09 (br, 4 H, NH), 9.79 (br, 4 H, NH) ppm. 13C NMR (100.5 MHz, THF-d8, 25 °C): δ = 30.00 (CH3), 31.63 (CCH3), 31.97 (CH3),

35.70 (CCH3), 50.71 (CH2), 57.94 (OCH3), 73.84 (CH2), 89.51, 91.97 (C≡C), 110.20,

110.41 (Py), 116.52, 120.28, 122.54, 122.73, 124.95, 127.54, 130.44 (Bn, meso-C),

131.39, 132.39 (pyrrole), 134.27, 135.68, 136.80 (Bn), 140.57 (Py), 145.03, 150.58,

150.67, 151.25 (Bn, Py), 151.66, 151.78 (pyrrole), 164.88, 170.77 (C=O) ppm.

MS (MALDI TOF, dctb): m/z = 2098 [M] +. EA: calc. (%) for C124H128N16O12Zn x 2 CH2Cl2 (2099.83) = C 66.20, H 5.65, Cl 6.41,

N 10.12, O 8.67, Zn 2.95; found: C 66.74, H 5.87, N 10.04.


(22800), 591.0 (5700).

IR (ATR): νmax = 2970, 2360, 2342, 1738, 1586, 1523, 1447, 1366, 1299, 1230,

1217, 1205, 1154, 1118, 996, 889, 797, 720 cm-1.

EXPERIMENTAL PART

132

Synthesis of Zinc-5,10,15,20-tetrakis-(4-ethynylphenyl)porphyrin 107:


added dropwise to a suspension of 84 (49.00 mg,

4.61 µmol) in dry toluene at RT. The reaction

mixture was allowed to proceed in the dark under

inert conditions for 2 d. The reaction mixture

showed very poor solubility therefore, no

extractions were attempted. 1H NMR analysis of the

crude product showed incomplete reaction and

desilylation with TBAF was repeated. Thus, a

solution of TBAF in THF (1 M, 0.60 mL) was added dropwise to a solution of the

crude reaction mixture in 20 mL of dry THF. The reaction was allowed to proceed for

2 d in the dark and under inert conditions. The solution was concentrated to dryness,

the residue was dissolved in 20 mL EtOAc and extracted two times with 20 mL of

aqueous solution of NaHCO3 (5%). The organic layer was separated, washed with

water (3 x 20 mL) and dried over Na2SO4. The solution was filtrated, concentrated

and purified by column chromatography (SiO2, EtOAc, Rf = 0.80).

Yield: 55.43 mg (99 %), pink powder. 1H NMR (400 MHz, THF-d8, 25 °C): δ = 3.83 (s, 4 H, C≡H), 7.91 d, 3JH,H = 8.1 Hz, 8

H, Bn), 8.25 (d, 3JH,H = 8.1 Hz, 8 H, Bn), 8.90 (s, 8 H pyrrole) ppm. 13C NMR (100.5 MHz, THF-d8, 25 °C): δ = 79.22, 83.80 (C≡C), 120.31, 122.18,

130.35 (meso-C, Bn), 131.72 (pyrrole), 134.75, 144.27 (Bn), 150.81 (pyrrole) ppm.

MS (MALDI TOF, dctb): m/z = 773 [M] +. EA: calc. (%) for C52H28N4Zn x 3 H2O (774.2) = C 75.41, H 4.14, N 6.76, O 5.80, Zn

7.90; found: C 75.14, H 5.12, N 5.12.


IR (ATR): νmax = 3295, 3030, 2970, 2926, 2854, 2360, 2342, 1738, 1605, 1525,

1491, 1456, 1366, 1261, 1207, 1179, 1104, 1072, 998, 907, 856, 809, 796, 769, 718

cm-1.

EXPERIMENTAL PART

133

Synthesis of the four-fold cyanuric acid functionalized porphyrin 111:

A solution of 51 in 1.40

mL of propionic acid was

heated at 100 °C. At this

temperature pyrrole

(19.17 µL, 0.28 mmol)

was added and the

reaction was heated at

reflux for 1 h. The crude

reaction mixture was

diluted with 3.5 mL of

THF, 100 mL of CHCl3

and washed with water (3

x 100 mL). The organic

layer was separated and


The product was purified by GPC column chromatography using THF as a solvent.

Yield: 3.80 mg (3 %), purple solid. 1H NMR (400 MHz, THF-d8, 25 °C): δ = -2.83 (br, 2 H, NH), 1.54 (m, 8 H, CH2) 1.81

(m, 8 H, CH2), 1.56 - 1.69 (m, 16 H, CH2), 3.70 (m, 8 H, OCH2), 4.39 (m, 8 H, NCH2),

8.10 (d, 3JH,H = 8.0 Hz, 8 H, Bn), 8.34 (d, 3JH,H = 8.1 Hz, 8 H, Bn), 8.74 (s, 8 H,

pyrrole β-H), 10.75 (s, 8 H, CONH). 13C NMR (100.5 MHz, THF-d8, 25 °C): δ = 26.24, 26.37, 28.14, 30.13 (CH2), 40.96

(OCH2), 65.23 (NCH2), 119.78, 128.16, 130.65, 134.73, 146.89 (meso-C, Bn),

148.48, 150.08, 166.11 (C=O).

MS (FAB): m/z = 1635 [M]+.

EXPERIMENTAL PART

134

Synthesis of the supramolecular complex 118: To 1.54 mg (5.63 x 10-4 mmol) of compound 93 suspended in 5 mL of CHCl3 (HPLC

grade), four equivalents of dendron 112 (1.49 mg, 22.52 x 10-4 mmol) were added.

The solution was stirred at RT for 13 h.

1H NMR (400 MHz, CDCl3, 25 °C): δ = -2.81 (br, 2 H, pyrrole NH), 0.83 – 2.43 (m, 88

H, CH2, CH3), 3.90 (m, 8 H, CH2N), 5.00 (d, 2JH,H = 12.1 Hz, 4 H, Bn-CH2), 5.07 (d, 2JH,H = 12.1 Hz, 4 H, Bn-CH2), 5.14 (d, 2JH,H = 12.0 Hz, 4 H, Bn-CH2), 5.20 (d, 2J =

12.1 Hz, 4 H, Bn-CH2), 5.80 (d, 3J = 2.81 Hz, 4 H, CH*), 5.89 (d, 3JH,H = 2.81 Hz, 4 H,

CH*), 7.07 – 7.39 (m, 48 H, Bn, Bz), 7.49 (m, 4 H, Bz), 7.85 (dd, 3JH,H = 8.1 Hz, 8 H,

Py), 7.87 (d, 3JH,H = 8.1 Hz, 8 H, Bz), 8.02 (d, 3JH,H = 8.1 Hz, 8 H, Py) , 8.14 (d, 3JH,H =

8.2 Hz, 8 H, Py), 8.21 (s, 8 H, Bn) 8.37 (br, 8 H, Bn), 8.54 (br, 8 H, Bn), 8. 61 (s, 4 H,

Bn-CH), 8.87 (br, 8 H, pyrrole β-H), 9.51 (br, 8 H, CONH), 10.03 (br, 8 H, CONH).

UV/Vis (CHCl3): [λ/nm] (ε/lmol-1cm-1) = 302.0 (98000), 421.5 (142000), 518.5 (7000),

552.5 (4000), 591.5 (2000), 647.5 (2000).


grade), four equivalents (1.49 mg, 22.52 x 10-4 mmol) of dendron 113 were added.


1H NMR (400 MHz, CDCl3, 25 °C): δ = -2.81 (br, 2 H, pyrrole NH), 0.83 – 2.43 (m, 88

H, CH3, CH2), 3.93 (m, 8 H, CH2N), 5.09 (d, 2JH,H = 12.0 Hz, 4 H, Bn-CH2), 5.16 (d, 2JH,H = 12.0 Hz, 4 H, Bn-CH2), 5.22 (d, 2JH,H = 12.0 Hz, 4 H, Bn-CH2), 5.28 (d, 2JH,H =

12.0 Hz, 4 H, Bn-CH2), 5.80 (d, 3JH,H = 2.81 Hz, 4 H, CH*), 5.88 (d, 3JH,H = 2.81 Hz, 4

H, CH*), 7.06 – 7.44 (m, 48 H, Bn, Bz), 7.51 (m, 4H, Bz), 7.84 (dd, 3JH,H = 7.9 Hz, 8

H, Py), 7.9 (d, 3JH,H = 7.9 Hz, 8 H, Bz), 8.11 (d, 3JH,H = 8.2 Hz, 8 H, Py), 8.13 (d, 3JH,H = 8.2 Hz, 8 H, Py), 8.21 (s, 8 H, Bn), 8.32 (br, 8 H, Bn), 8.52 (br, 8 H, Bn), 8.56

(br, 4 H, Bn), 8.83 (br, 8 H, pyrrole β-H) 9.48 (br, 8 H, CONH), 9.99 (br, 8 H, CONH).


552.0 (4000), 592.5 (2000), 649.0 (2000).

EXPERIMENTAL PART

135


grade), four equivalents (3.47 mg, 22.52 x 10-4 mmol) of dendron 114 were added.


1H NMR (400 MHz, CDCl3, 25 °C): δ = -2.88 (br, 2 H, pyrrole NH), 0.84 – 2.42 (m,

152 H, CH3, CH2), 3.15 (m, 24 H, CH2N), 3.84 (br, 4 H, CONH), 5.01 (d, 2JH,H = 3.1

Hz, 4 H, Bn-CH2), 5.03 (d, 2JH,H = 3.1 Hz, 4 H, Bn-CH2), 5.09 (d, 4 H, Bn-CH2), 5.10

(d, 4 H, Bn-CH2), 5.16 (d, 2JH,H = 1.9 Hz, 4 H, Bn-CH2), 5.19 (d, 2JH,H = 2.7 Hz, 8 H,

Bn-CH2), 5.22 (d, 2JH,H = 2.8 Hz, 4 H, Bn-CH2), 5.69 (d, 3JH,H = 3.7 Hz, 4 H, CH*),

5.77 (d, 3JH,H = 2.8 Hz, 8 H, CH*), 5.79 (d, 3JH,H = 2.8 Hz, 4 H, CH*), 5.88 (d, 3JH,H =

2.9 Hz, 4 H, CH*), 5.90 (d, 3JH,H = 2.8 Hz, 4 H, CH*), 6.21 (br, 4 H, CONH); 7.06 -

7.56 (116 H, Bn, Bz), 7.89 (dd, 8 H, Py), 7.97 (m, 16 H, Bz), 8.00 (m, 24 H, Bz, Py-

CH), 8.12 (d, 3JH,H = 7.9 Hz, 8 H, Py-CH), 8.21(s, 8 H, Bn-CH), 8.34 (br, 8 H, Bn-CH),

8.52 (br, 12 H, Bn-CH), 8.85 (br, 8 H, pyrrole β-H), 9.48 (br, 8 H, CONH), 10.02 (br, 8

H, CONH).


552.5 (3000), 592.0 (2000), 648.0 (2000).




1H NMR (400 MHz, CDCl3, 25 °C): δ = -2.88 (br, 2 H, pyrrole NH), 0.85 – 2.42 (m,

152 H, CH2, CH3), 3.18 (m, 24 H, CH2N), 3.84 (br, 4 H, CONH), 5.01 (d, 2JH,H = 4.5

Hz, 4 H, Bn-CH2), 5.05 (d, 2JH,H = 4.5 Hz, 4 H, Bn-CH2), 5.09 (d, 2JH,H = 3.0 Hz, 4 H,

Bn-CH2), 5.12 (d, 2JH,H = 2.4 Hz, 4 H, Bn-CH2), 5.16 (d, 2JH,H = 3.1 Hz, 4 H, Bn-CH2),

5.20 (d, 2JH,H = 3.8 Hz, 8 H, Bn-CH2), 5.23 (d, 2JH,H = 3.8 Hz, 4 H, Bn-CH2), 5.69 (d, 3JH,H = 3.7 Hz, 4 H, CH*), 5.78 (d, 3JH,H = 2.8 Hz, 8 H, CH*), 5.81 (d, 3JH,H = 2.8 Hz, 4

H, CH*), 5.89 (d, 3JH,H = 2.8 Hz, 4 H, CH*), 5.92 (d, 3JH,H = 2.8 Hz, 4 H, CH*), 6.22

(br, 4 H, CONH), 7.10 – 7.53 (116 H, Bn, Bz), 7.90 (dd, 8 H, Py), 7.92 (m, 16 H, Bz),

8.00(m, 24 H, Bz, Py), 8.11 (d, 3JH,H = 8.0 Hz, 8 H, Py) 8.21 (s, 8 H, Bn), 8.24, (br, 8

EXPERIMENTAL PART

136

H, Bn), 8.65 (br, 8 H, Bn), 8.81 (s, 4 H, Bn), 8.87 ( br, 8 H, pyrrole β-H), 9.48 (br, 8 H,

CONH), 10.02 (br, 8 H, CONH).


552.0 (3000), 592.0 (2000), 648.0 (2000).




1H NMR (400 MHz, CDCl3, 25 °C): δ = -2.82 (br, 2 H, pyrrole NH), 0.83-2.45 (m, 280

H, CH2, CH3), 3.18 (m, 56 H, CH2N), 3.84 (br, 16 H, CONH), 5.18 (m, 64 H, Bn-CH2),

5.87 (m, 56 H, CH*), 6.62 (br, 8 H, CONH), 7.07 - 8.01 (m, 324 H, Bn, Bz, Py), 8.10

(d, 8 H, Py), 8.21 (s, 8 H, Bn), 8.32 (br, 8 H, Bn), 8.54 (br, 12 H, Bn), 8.84 (br, 8 H,

pyrrole β-H), 9.50 (br, 8 H, CONH), 9.96 (br, 8 H, CONH).


421.5 (109000), 517.0 (6000), 553.0 (3000), 592.0 (2000), 648.0 (1000).




1H NMR (400 MHz, CDCl3, 25 °C): δ = -2.83 (v. br, 2 H, pyrrole NH), 0.84-2.46 (m,

280 H, CH2, CH3), 3.15 (m, 56 H, CH2N), 5.17 (m, 64 H, Bn-CH2), 5.84 (m, 56 H,

CH*), 6.60 (br, 8 H, CONH), 7.06 - 8.02 (m, 324 H, Bn, Bz, Py), 8.09 (d, 8 H, Py),

8.21 (s, 8 H, Bn), 8.25 (br, 8 H, Bn), 8.53 (m, 12 H, Bn), 8.83 (br, 8 H, pyrrole β-H),

9.44 (br, 8 H, CONH), 9.95 (br, 8 H, CONH).


422.0 (109000), 517.0 (6000), 552.5 (3000), 592.0 (2000), 648.5 (1000).

LITERATURE

137

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DANKSAGUNG An dieser Stelle möchte ich mich nochmals bei meinem Doktorvater Prof. Dr. Andreas Hirsch für die Vergabe des Themas und das beständige Interesse am Fortgang dieser Arbeit, sowie für die Möglichkeit die Themenstellung weitgehend selbstständig zu bearbeiten, herzlich bedanken. Besonders bedanken möchte ich mich bei den akademischen Räten Dr. Marcus „Specki“ Speck (vielen Dank für die schönen Feiern), Dr. Michael „Breddl“ Brettreich (v.a. für die Korrektur dieser Arbeit und fürs fleissige Einkaufen ☺), Dr. habil Norbert „Nobbi“ Jux (für die zahlreichen Ratschläge in porphyrintechnischen Problemen). Ein großer Dank gilt auch den Angestellten und Mitarbeitern des Instituts für organische Chemie. Hervorzuheben sind hierbei: Frau Erna Erhardt, Dr. Otto Vostrovsky (Wann kommt ihr uns denn mal in Zypern besuchen?), Dr. T. Röder (der Experte in Sachen Wetter), Dr. F. Hauke, Prof. Dr. Walter „Waldi“ Bauer, Wilfried Schätzke und Christian Placht (vielen Dank für die unzähligen Messungen), Wolfgang „Don“ Donaubauer (danke für die schnellen Messungen „zwischendurch“), Frau M. Dzialach, Frau E. Hergenröder, Detlef Schagen (nicht immer Praktikanten ärgern ☺), das Magazin-Team Herr R. Panzer und Frau H. Oschmann, das Werkstatt-Team Herr E. Schreier und Herr Ruprecht (danke für die schnellen Reparaturen und Instandhaltungen), die Glasbläser Herr Fronius und Herr Saberi (danke für die schnellen Reparaturen und Spezialanfertigungen) und unserm Hausmeister Holger. Desweiteren möchte ich mich bei den Mitarbeitern externer Institute für ihre Hilfestellung und Untersuchungen bedanken. Hervorzuheben sind hierbei: Prof. Dr. Dirk M. Guldi, Dipl. Chem. Bruno Grimm, Dr. Nikos Chronakis und Dr. Rainer Waibl und Prof. Dr. F. Würthner. Weiterhin möchte ich allen Kollegen aus dem Arbeitskreis für die schöne Arbeits- und „Party“-Zeit in der OC danken: Dr. Jürgen „Abe“ Abraham (die „goldenen“ Zeiten des Labors), Dr. Domenico „Nick“ Balbinot (offizieller AK-Schönster), Dr. Christian Betz, Dr. Thorsten Brandmüller (unser Grillmeister), Dr. Stephan „Budgie“ Burghardt, Dr. Boris „Bobu“ Buschhaus (die Ruhe und Harmonie in Person), Dr. Siegfried „Sciguy“ Eigler, Dr. Alexander Franz, Dr. Matthias Helmreich, Dr. Michael „Kelly“ Kellermann, Dr. Christian „Klingo“ Klinger, Dr. Hanaa Mansour, Dr. Elena Ravanelli, Dr. Jürgen „Schmitti“ Schmidt, Dr. Kristine „Spülmaus“ Hartnagel (Benchnachbarin in den guten und schlechten Zeiten ☺ ), Dr. Uwe Hartnagel (Danke für die schönersten Fotos ! ☺), Dr. Adrian „Eternal“ Jung, Dr. Jörg Dannhäuser (Porphyrine sind schwul), Claudia Backes, Dr. Miriam Becherer (geteilter Heimweg war schönerer Heimweg ☺), Dr. Florian Beuerle, Maria Alfaro Blasco, Christine Böhner, Helmut „Spanienophil“ Degenbeck, Katharina Dürr, Alexander „Kai“ Ebel (stets hilfsbereiter Labornachbar), Jan-Frederick „Fry“ Gnichwitz (Was geht in der Artilleriestrasse?), Felix „Flix“ Grimm (Laborluftveredler?! ☺), Frank Hörmann, Dr. Stefan „Steffele“ Jasinski, Christian „Kovi“ Kovacs, Dr. Nina Lang (war immer schön ein Bierchen mit Dir zu trinken), Dr. Jutta Jusie Rath (Danke für die schöne Studi-und Party-Zeit ☺), Phillip Rath („auch wieder im Lande?“), Dr. Karin „KaRo“ Rosenlehner, Michaela „ Mischi“ Ruppert, Cordula „Cordu“ Schmidt (immer dieser CD-Effekt....), Marion Schmidt, Thorsten „Schunky“ Schunk (Seitenbiß?!), Zois Syrgiannis, Natalia Tokatly, Nadine „Naddel“ Ulm, Dr. Florian „Wessi“ Wessendorf, Dr. Patrick „Keulo“ Witte, Dr. David „Dave“

Wunderlich, Christoph Dotzer, Benjamin Gebhardt, Alexander Gmehling, Sebastian Schlundt, Stefanie Bade, Miriam „Miri“ Biedermann, Rainer „Fürst“ Lippert, Astrid Hopf und Lennard Wasserthal. Danke auch an die Post-Docs und Post-Profs.: Dr. Nikos Chronakis, Prof. Dr. Giannis Elemes, Dr. Haruhito Kato, Dr. Arnaudt Mentec und Dr. FengLai. Weiterer Dank geht auch an meine fleißigen Mitarbeiter: Andreas Beyer und die Mowis Nicole Fischer und Alexander Speer. Zum Schluss möchte ich meinen Freunden und ganz besonders meiner Familie und μωρό μου danken, die mir tapfer in den „chemischen Durststrecken“ beigestanden haben.

CURRICULUM VITAE

Persönliche Daten

Name: Katja Maurer-Chronakis

Geburtsdatum: 10/12/1976

Geburtsort: Nürnberg

Staatsangehörigkeit Deutsch

Familienstatus: Verheiratet

Schulbildung und berufliche Ausbildung

09/1984-07/1988 Dunant-Grundschule Nürnberg

09/1988-07/1996 Abitur am Labenwolf-Gymnasium Nürnberg

09/1996-08/1999 Ausbildung als Chemielaborant am Institut für Mineralogie

der Friedrich-Alexander-Universität Erlangen-Nürnberg

Studium

11/1999-11/2001 Grundstudium der Chemie an der Friedrich-Alexander-

Universität Erlangen-Nürnberg

12/2001-01/2004 Hauptstudium der Chemie an der Friedrich-Alexander-

Universität Erlangen-Nürnberg

01/2004-10/2004 Diplomarbeit am Institut für Organische Chemie der

Friedrich-Alexander-Universität unter der Anleitung von Prof.

Dr. Andreas Hirsch

Thema:“Synthese und Charakterisierung eines

Tetraphenylporphyrinderivats mit vier peripheren

Hamiltonrezeptoren”.

10/2004-06/2010 Anfertigung der Doktorarbeit am Institut für Organische

Chemie der Friedrich-Alexander-Universität unter der

Anleitung von Prof. Dr. Andreas Hirsch. Thema: “Synthesis of

Cyanuric Acid and Hamilton Receptor Substituted

Tetraphenylporphyrins: Investigation on the Chiroptical and

Photophysical Properties of their Self-assembled

Superstructures with Depsipeptide and Fullerene

Dendrimers”.

PUBLIKATIONSLISTE „Self-assembly and Chiroptical Properties of Chiral Dendrimers Consisting of a Hamilton Receptor Substituted Porphyrin and Depsipeptide Cyanurates” K. Maurer, K. Hager, A. Hirsch, Eur. J. Org. Chem. 2006, 3338.

“Self-assembling Depsipeptide Dendrimers and Dendritic Fullerenes with New Cis- and Trans Symmetric Hamilton Receptor Functionalized Zinc-porphyrins: Synthesis, Photophysical Properties and Cooperativity Phenomena K. Maurer, B. Grimm, F. Wessendorf, D. M. Guldi, A. Hirsch, Eur. J. Org. Chem,

2010, 5010.

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