Template-directed self-assembly by way of molecular recognition at the micellar–solvent interface:...

Registered Charity Number 207890

Accepted Manuscript

This is an Accepted Manuscript, which has been through the RSC Publishing peer review process and has been accepted for publication.

Accepted Manuscripts are published online shortly after acceptance, which is prior to technical editing, formatting and proof reading. This free service from RSC Publishing allows authors to make their results available to the community, in citable form, before publication of the edited article. This Accepted Manuscript will be replaced by the edited and formatted Advance Article as soon as this is available.

To cite this manuscript please use its permanent Digital Object Identifier (DOI®), which is identical for all formats of publication.

More information about Accepted Manuscripts can be found in the Information for Authors.

Please note that technical editing may introduce minor changes to the text and/or graphics contained in the manuscript submitted by the author(s) which may alter content, and that the standard Terms & Conditions and the ethical guidelines that apply to the journal are still applicable. In no event shall the RSC be held responsible for any errors or omissions in these Accepted Manuscript manuscripts or any consequences arising from the use of any information contained in them.

www.rsc.org/obc

ISSN 1477-0520

Organic &BiomolecularChemistry

1477-0520(2010)8:3;1-H

FULL PAPER Shuji Ikeda et al.Hybridization-sensitive fluorescent DNA probe with self-avoidance ability

PERSPECTIVELaurel K. Mydock and Alexei V. DemchenkoMechanism of chemical O-glycosylation: from early studies to recent discoveries

www.rsc.org/obc Volume 8 | Number 3 | 7 February 2010 | Pages 481–716

Organic &BiomolecularChemistry

View Article OnlineView Journal

This article can be cited before page numbers have been issued, to do this please use: M. A. Olson, J. R. Thompson, T. J.Dawson, C. Hernandez, M. Messina and T. O'Neal, Org. Biomol. Chem., 2013, DOI: 10.1039/C3OB41467A.

http://www.rsc.org/Publishing/Journals/guidelines/AuthorGuidelines/JournalPolicy/accepted_manuscripts.asp

http://www.rsc.org/help/termsconditions.asp

http://www.rsc.org/Publishing/Journals/guidelines/EthicalGuidelines/index.asp

http://dx.doi.org/10.1039/c3ob41467a

http://pubs.rsc.org/en/journals/journal/OB

Table of Contents Entry

Templated micellisation of bipyridinium-based amphiphiles triggered by donor-acceptor

interactions results in augmented hydrodynamic diameters, ζ-potentials, surface

pressures and more!

Page 1 of 11 Organic & Biomolecular Chemistry

Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.

View Article OnlineDOI: 10.1039/C3OB41467A


Journal Name

Cite this: DOI: 10.1039/c0xx00000x

www.rsc.org/xxxxxx

Dynamic Article Links ►

ARTICLE TYPE

This journal is © The Royal Society of Chemistry [year] [journal], [year], [vol], 00–00 | 1

Template-Directed Self-Assembly by way of Molecular Recognition at

the Micellar-Solvent Interface: Modulation of the Critical Micelle

Concentration

Mark A. Olson, * Jonathan R. Thompson , Trenton J. Dawson,

Chris M. Hernandez,

Marco S. Messina,

and Travis O’Neal 5

Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX

DOI: 10.1039/b000000x

By incorporating the concepts of structural preorganisation and complementarity in concert with non-

covalent donor-acceptor [] and hydrophobic interactions, a duo of -electron deficient bipyridinium-

based linear and gemini amphiphiles capable of responding to molecular templation have been designed 10

and synthesised. When combined with -electron rich di(ethylene glycol)-disubstituted 1,5-

dihydroxynapthalene, a dramatic decrease in the critical aggregation concentration by 66% was

observed with concomitant increases in the hydrodynamic diameter, -potential, and Langmuir surface

pressures of the micellar solutions thus enhancing the detergents’ efficiency and effectiveness at

lowering the surface tension of water. By employing a phase separation model that takes into account the 15

degree of counterion binding to the micellar aggregate superstructure, the effects of donor-acceptor

templation on the Gibb’s free energy of micellisation (GM) for the amphiphiles was quantified. It was

found that donor-acceptor templation was capable of lowering GM by up to 1.75 kcal mol1 at which

point it was observed, while under the influence of molecular templation, that linear single hydrophobic

tailed detergent molecules exhibit properties characteristic of double-tailed phospholipid-like gemini 20

surfactants.

Introduction

The controlled self-assembly of organic molecules into discrete

supramolecular architectures continues to impact research and

development in the areas of chemistry, materials science, and 25

molecular nanotechnology.1 By making use of a clutch of non-

covalent bonding interactions in which donor-acceptor [-],

[CH-O], [CH-], and hydrophobic interactions are all

orchestrated to a high degree of precision it is now possible to

design synthetic surfactant systems whose adjustable properties 30

are now starting to more closely resemble and mirror the

adaptable physiological dynamics of their biological counterparts,

for example pulmonary surfactant matrixes and various other

phospholipids.2 By utilising established structure-property

relationships3 whereby subtle synthetic manipulations can have a 35

huge impact on performance and molecular functionality, the

stage has been set to usher in new classes of surfactants whose

properties and performance characteristics can be easily

modulated without the need of covalent modifications.4

The detergency effect of surfactants is manifested by their self-40

assembly into higher ordered structures known as micelles. Of the

many non-covalent interactions that play a role in surfactant self-

assembly, hydrophobic interactions are the primary driving force

whereby the entropic penalty for micelle assembly is less than the

entropic penalty for solvating the entire surfactant with water 45

molecules. The conditions for surfactant self-assembly thus are

governed by the concentration of the amphiphiles in solution, the

concentration at which the first aggregation process occurs being

known as the critical micelle concentration (CMC) and 50

subesquent aggregation occurring at the critical aggregation

concentration (CAC). The process of micellisation can be

modeled5 most easily using a molecular thermodynamic (MT)

theoretical approach in which the free energy for micellisation

(GM) can be expressed as the sum of at least six different free 55

energy contributions namely the transfer free energy of the

surfactant tail, interfacial micellar aggregate core-water free

energy, packing free energy of the surfactant tail, as well as the

surfactant head-group steric, head-group electrostatic, and head-

group dipole interactions expressed per mole of surfactant. 60

Given this thermodynamic treatment of surfactant self-assembly,

only the transfer free energy is large, negative and favourable.

With exception to the aggregate core-water interfacial free energy

which decreases with increasing aggregation number providing

positive cooperativity favoring micellar growth to larger sizes 65

all of the other free energy contributions to GM are positive. It

is these free energy contributions which grow more positve with

increasing aggregation number leading to negative cooperativity

that ultimately limits the micellar aggregates to definite sizes. For

someone attempting to exert control over the micellisation 70

Page 2 of 11Organic & Biomolecular Chemistry

Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.



2 | Journal Name, [year], [vol], 00–00 This journal is © The Royal Society of Chemistry [year]

process, its onset, and the size and shape of the aggregate

superstructures, these are the most important free energy

contributors which must be targeted for modulation.

The electrostatic free energy contribution to micellisation

which is typically opposing and repulsive in nature stemming 5

from the charged (anionic or cationic) surfactant head group is

arguably6 one of the easiest free energy contributors to target for

modulation. It becomes clear then that any external stimuli driven

process which can serve to decrease the repulsive electrostatic

interactions between contiguous surfactant polar head groups can 10

serve as the foundation for the molecular modulation of the

critical micelle concentration as well as both the micellar size and

shape. Supramolecular donor-acceptor complexes are a perfect

candidate for minimising electrostatic repulsions among

surfactant head groups. 15

Thus in our own laboratory we have turned our attention to this

concentration dependent aggregation behaviour of amphiphiles in

aqueous solvent in an effort to control precisely their

intermolecular interactions at the air-water interface and the

emergence of supramolecular aggregates. Our efforts were 20

motivated in part by recent advances7 in developing donor-

acceptor supramolecular systems based on the binding

interactions of -electron deficient bipyridiniums with -electron-

rich molecular guests and the recent reemergence of

bipyridinium-based detergents both in aqueous environments and 25

mixed aqueous-organic solvent systems in which, for example,

the complexation of the bipyridinium head group of the surfactant

with cucurbit[6]uril,8 cyclodextrins,9 and electron rich groups6

have been used to trigger the spontaneous formation of vesicles

and ultralong nanofibers. While these examples have focused on 30

the characterisation of the supramolecular aggregate species, we

have become more interested in these similar donor-acceptor

interactions and their effects and behaviour at the air-water

interface and the thermodynamics which govern the assembly of

increasingly larger templated micellar aggregates as a result of 35

modulating the CMC. The research reported herein describes a

detergent binary blend in which the surface activity and the CAC

of two bipyridinium-based amphiphiles a dicationic linear

surfactant 12+ and a tetracationic gemini10 surfactant 24+ can be

easily modulated by employing the principles of preorganisation1 40

and template-directed self-assembly1 in aqueous solutions upon

the addition of an electron rich additive. Characterisation of the

micellar nanostructures and their self-assembly by surface tension

(ST), conductometry, NMR spectroscopy, dynamic light

scattering (DLS), and -potential measurements confirmed the 45

presence of two aggregation processes of which only one,

occurring at higher detergent concentrations, responds to

template-directed coercion resulting in dramatic decreases in the

CAC concomitant with increases in the hydrodynamic diameter

and -potential of the micellar aggregates, as well as increases in 50

the Langmuir surface pressures.

Experimental

General

Starting materials and reagents were purchased from commercial

suppliers and used as received. Compounds 3+ and di(ethylene 55

glycol)-disubstituted 1,5-dihydroxynaphthalene (DNP- DEG)

Scheme 1 Graphical representations (top left) and the synthesis of the

bipyridinium-based single-tailed dicationic amphiphile 12+ (top right) and

double-tailed gemini tetracationic amphiphile 24+.

were synthesised following procedures reported11,12 in the 60

literature. All reactions were performed under an argon

atmosphere and in dry solvents unless otherwise noted.

Analytical thin-layer chromatography (TLC) was performed on

aluminum sheets, precoated with silica gel 60-F254 (Merck 5554).

Flash chromatography was carried out using silica gel 60 65

(230−400 mesh) as the stationary phase. Deuterated solvents

(Cambridge Isotope Laboratories) for NMR spectroscopic

analyses were used as received. 1H and 13C NMR spectra were

recorded on a Bruker Avance 300 MHz spectrometer. Chemical

shifts are reported in ppm relative to the residual signal of the 70

solvent (D2O: δ 4.79 ppm). High resolution electrospray

ionisation (HRESI) mass spectral analyses were performed by the

Mass Spectrometry Facility of the Department of Chemistry and

Biochemistry at the University of Texas at Austin. Surface

tension measurements were performed on a CSC Precision 75

DuNoüy ring tensiometer. All surface tension samples were

allowed to equilibrate for 24 hours. UV-Vis spectra were

recorded on a Varian CARY 100BIO temperature-controlled

spectrophotometer in a 1 cm disposable cuvette with a 5 mm path

length at 298 K. Dynamic laser light scattering, and laser Doppler 80

electrophoresis (for the determination of -potential and

electrophoretic mobility) measurements were performed using a

Malvern Nano Series Zetasizer Nano-ZS at a scattering angle of

() of 173°. All solvents used for dynamic laser light scattering

and laser Doppler electrophoresis were filtered through a 85

Whatman Anotop 25 inorganic membrane filter with a 0.02 m

pore size prior to sample preparation. Conductivity measurements

were performed on a Thermo Orion 550 equipped with a

conductivity cell.

Synthesis of 12+ and 24+ 90

12+: Monomethylated viologen 3+ (10.0 g, 33.5 mmol) and 11-

bromo-1-undecene (15.56 g, 67.0 mmol, 14.64 ml) were added to

dry degassed DMF (130 mL) and heated at 80° C while stirring

for 24 hours. The reaction mixture was cooled and a red

precipitate was collected by filtration. The red precipitate was 95


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.



This journal is © The Royal Society of Chemistry [year] Journal Name, [year], [vol], 00–00 | 3

washed with DMF and ethyl ether three times each and dried in

vacuo to afford the dicationic product 12+ (10.56 g, 59%) as an

orange/red bromide-iodide mixed counterion salt. Counterion

exchange: The solid was then taken up in hot H2O and a saturated

solution of NH4PF6 in H2O was added dropwise until no further 5

precipitate formed. The white precipitate was then filtered and

dissolved in a minimal amount of MeCN. A saturated solution of

tetrabutylammonium bromide (TBABr) in MeCN was then added

dropwise until no further precipitate formed. The precipitate was

then filtered and dried in vacuo to afford the dibromide salt as a 10

yellow solid. Mp: 259262 C. 1H NMR (D2O, 300 MHz, 25 °C):

δ = 1.29 (s, 6H), 1.37 (s, 6H), 2.00 (m, 4H), 4.51 (s, 3H), 4.73 (t,

J = 7.37 Hz, 2H), 4.97 (d, J = 10.02 Hz, 2H), 5.01 (d, J = 17.18

Hz, 2H), 5.91 (m, 1H), 8.54 (t, J = 6.09 Hz, 4H), 9.06 (d, J = 5.81

Hz, 2H), 9.12 (d, J = 5.81 Hz, 2H); 13C NMR (D2O, 100 MHz, 25 15

°C): δ = 26.03, 28.86, 28.91, 29.09, 29.32, 29.35, 31.16, 33.72,

48.58, 62.04, 114.42, 126.88, 127.27, 139.13, 145.56, 146.39,

149.47, 149.92; LRMS (ESI): m/z calcd for C22H32N2: 324.2560;

found: 324.3 [MBrI]+; HRMS (ESI): m/z calcd for C22H32N2:

324.2560; found: 324.2561 [MBrI]+. 20

Mono-undecylated bipyridine: 4,4’-Dipyridyl (20.0 g, 128

mmol) was dissolved in dry degassed DMF (80 mL), and the

solution was heated at 90 °C. 11-bromo-1-undecene (29.7 g, 128

mmol) in dry degassed DMF (40 mL) was then added dropwise 25

to the reaction. The reaction was stirred for an additional 24 h.

The reaction mixture was cooled and a yellow precipitate was

removed by filtration. The DMF filtrate was evaporated under

reduced pressure, resulting in a brown oil out of which the title

compound crystallised upon standing. This solid was taken and 30

pulverised in toluene (150 mL) via sonication. The toluene/solid

mixture was filtered and the solid was then washed with toluene

and diethyl ether three times each and dried in vacuo to afford the

monocationic product 4+ (31.85 g, 64%) as a light tan solid. Mp:

6667 C. 1H NMR (D2O, 300 MHz, 25 °C): δ = 1.22 (s, 6H), 35

1.31 (s, 6H), 1.802.00 (m, 4H), 4.65 (t, J = 7.22 Hz, 2H),

4.895.00 (m, 2H), 5.84 (m, 1H), 7.91 (d, J = 6.25 Hz, 2H), 8.41

(d, J = 6.25 Hz, 2H), 8.77 (d, J = 6.25 Hz, 2H), 8.96 (d, J = 6.25

Hz, 2 H); 13C NMR (D2O, 100 MHz, 25 °C): δ = 25.02, 27.88,

28.09, 28.15, 28.22, 28.25, 30.35, 33.03, 61.68, 113.91, 122.44, 40

125.95, 140.24, 142.53, 144.74, 149.99, 153.68; LRMS (ESI):

m/z calcd for C21H29N2: 309.2325; found: 309.3 [MBr]+; HRMS

(ESI): m/z calcd for C21H29N2: 309.2325; found: 309.2327

[MBr]+.

45

24+: Mono-undecylated bipyridine (10.0 g, 25.7 mmol) and α,α’-

dibromo-p-xylene (1.70g, 6.44 mmol) were combined in dry

degassed DMF (100 mL) and the mixture was heated at 80 C

while stirring for 24 h. The reaction mixture was cooled and a

yellow precipitate was collected by filtration. The yellow 50

precipitate was then washed with DMF and ethyl ether three

times each and dried in vacuo to afford the tetracationic product

24+ (6.45 g, 96%) as a yellow solid. Mp: 292293 C. 1H NMR

(D2O, 300 MHz, 25 °C): δ = 1.221.32 (br d, 24H), 1.912.05 (br

m, 8H), 4.71 (t, J = 7.44 Hz, 4H), 4.824.96 (m, 4H), 5.80 (m, 55

2H), 5.98 (s, 4H), 7.64 (s, 4H), 8.53 (t, J = 7.10 Hz, 8H), 9.10 (d,

J = 7.10 Hz, 4H), 9.17 (d, J = 7.10 Hz, 4 H) 13C NMR (DMF-d7,

100 MHz, 25 °C): δ = 24.97, 27.80, 28.09, 28.12, 28.14, 28.19,

30.40, 33.02, 62.34, 64.19, 113.88, 126.95, 127.10, 127.23,

130.35, 134.22, 140.33, 145.63, 149.70, 150.54; HRMS (ESI): 60

m/z calcd for C50H66Br2N4: 440.1828; found: 440.1825

[M2Br]2+.

Determination of the free energies of micellisation (GM)

Free energies of micellisation were calculated using the method

described by Zana13 and are reported per hydrophobic tail. The 65

following equation was used for all free energy calculations:

where R is the gas constant, T is the temperature in Kelvin, i is

the number of charged groups in the molecule, j is the number of

hydrophobic tails in the molecule, zs is the charge per charged

group, zc is the charge per counterion, = (m1 m2) / m1 where m1 70

is the slope of the graph of conductivity versus concentration

below the critical micelle concentration, m2 is the slope of the

graph of conductivity versus concentration above the critical

micelle concentration, and cmc is the critical micelle

concentration. 75

Results and discussion

Design and synthesis of the bipyridinium-based surfactants

In an effort to investigate the modulation of the CMC/CAC using

donor-acceptor interactions, we designed two π-electron deficient

bipyridinium-based surfactants capable of forming donor-80

acceptor complexes with π-electron rich guests. Compound 12+

was designed to bind a single molar equivalent of π-electron rich

guest when situated alongside and packed amongst other

molecules of 12+ at the micelle-solvent interface. Compound 24+,

a gemini surfactant, was designed to bind up to two molar 85

equivalents of π-electron rich guests, with a single guest residing

within the bipyridinium pocket and the other equally engaged in

along-side binding interactions at the packed micellar-solvent

interface. Terminal unsaturation of the hydrophobic tails was

employed for future polymerisation and/or oligomerisation, the 90

results of which will be discussed in a future communication.

However, it must be noted here that the effects of terminal

unsaturation on hydrophobic surfactant tails are reported14 to

result in a clear decrease in hydrophobicity equivalent to the

removal of 11.5 CH2 groups. 95

Synthetic routes to obtain compounds 12+ and 24+ were devised

as shown in Scheme 1. The dicationic amphiphile 12+ was

obtained in by the quaternisation of a known10 monomethyl

viologen derivative with excess 11-bromo-1-undecene in dry

degassed DMF at 80 C for 24 hours. Counterion exchange of the 100

mixed IBr counterion to the hexafluorophosphate salt using

NH4PF6 in water followed by a subsequent counterion exchange

to the dibromide salt using TBABr in MeCN gave the desired

dicationic surfactant 12+ in 59% yield. The tetracationic

amphiphile 24+ was made in 61% overall yield over two steps 105

beginning with monoquaternisation of 4,4-bipyridine with

equimolar 11-bromo-1-undecene in dry degassed DMF at 90 C

for 24 hours. A two-fold quaternisation of the mono-undecylated

bipyridine, obtained in 64% yield in the first step, with α,α-

dibromo-p-xylene in dry degassed DMF at 80 C over 24 hours 110

gave the desired tetracationic product 24+ in 96% yield.


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.




Fig.1 Molecular structure of DNP-DEG and the graphical representation

of the donor-acceptor binding interactions between 12+ (process I) and 24+

(Process II and III) with DNP-DEG.

All of the surfactants and their precursors were characterised by 1H NMR, 13C NMR, and HRMS. 5

Determination of the CMC and the CAC

Critical micelle concentrations (CMCs) were determined at 298 K

by means of surface tension (ST) and conductivity measurements

(Table 1). Plots of ST versus the log concentration for both 12+

and 24+ revealed sharp inflections corresponding to CMCs of 29.8 10

2.0 mM and 9.0 1.0 mM and Langmuir surface pressures of

15.7 0.3 mN m-1 and 25.5 0.3 mN m-1 respectively. As

expected, the covalent preorganisation of two amphiphile chains

in gemini8 surfactant 24+ resulted in a dramatic decrease in its

CMC and an increase in the Langmuir surface pressure producing 15

a detergent which was more efficient15 and effective15 at lowering

the surface tension of water. We were surprised to discover that

the CMCs obtained at higher concentrations actually reflected a

second critical aggregation concentration (CAC)16 when variable

concentration conductivity experiments at 298 K revealed 20

transitions at much lower concentrations for 12+ and 24+ at 2.73

0.24 mM and 2.77 0.15 mM respectively. It is known17 that

amphiphiles typically undergo several concentration-based self-

assembly processes the first yielding spherical-like micelles

and a second at much higher concentrations yielding larger 25

cylindrical-type structures. However earlier reports18 on similar

bipyridinium-based amphiphilic compounds did not reveal the

existence of both a lower CMC and a higher CAC.

Probing the donor-acceptor interactions

-Electron deficient bipyridinium-based derivatives such as 12+ 30

and 24+ are known19 to form stable donor-acceptor - stacking

complexes with -electron rich dihydroxynaphthalene (DNP)

containing compounds. The DNP-bipyridinium binding motif has

been exploited in the template-directed synthesis of mechanically

interlocked compounds20 and the formation of host-guest 35

complexes in solution,19 at the side-chains of polymers,21 and at

the metal nanoparticle-solvent interface.22 Di(ethylene glycol)-

disubstituted 1,5-dihydroxynaphthalene (DNP-DEG) was thus

chosen as an appropriate agent capable of lowering the Gibbs free

energy of micellisation (GoM)5b,13,23 by mitigating Coulombic 40

repulsion among contiguously assembled amphiphiles acting as

molecular glue for the hydrophilic amphiphile head groups (Fig.

1 process IIII). The addition of the template results in the

triggering of micellar aggregate formation at substantially lower

detergent concentrations, whereby 12+ can benefit by the addition 45

Fig. 2 (a) UV-Vis absorption spectra of 12+ (1102 M) with the addition

of 1 molar equivalent of DNP-DEG (black trace) and 24+ (3103 M) with

the addition of 1 (red trace) and 2 (green trace) molar equivalents of

DNP-DEG recorded in H2O at 298 K; (b) Photographs of vials containing

1102 M solutions of 12+(A) and 12+ with 1 molar equivalent of DNP-50

DEG (B) and 5103 M solutions of 24+ (C) and 24+ with 1 (D) and 2 (E)

molar equivalents of DNP-DEG in H2O taken 5 minutes after vigorous

shaking. The visible colour change is due to donor-acceptor charge-

transfer between the π-electron deficient bipyridinium amphiphile head

groups and the π-electron rich DNP-DEG template. The stable formation 55

of closed-cell foam indicates that the Marangoni effect and the detergency

of the solution have been augmented.

of 1 molar equivalent of DNP-DEG (Fig. 1 process I) and 24+ can

bind up to 2 molar equivalents of DNP-DEG (Fig. 1 process II

and III) with one equivalent residing within the bipyridinium 60

pocket and the other equivalent equally engaged in alongside

intermolecular binding interactions.24

Upon addition of DNP-DEG to solutions of 12+ and 24+, a

dramatic colour change (Fig. 2b) occurred, stemming from the

donor-acceptor charge transfer interactions between the 65

bipyridinium surfactant head groups and DNP-DEG –strong

evidence19 indicating that molecular recognition and

complexation has taken place. The band gaps for the charge

transfer interaction between the detergents and the template were

measured at 2.79 eV, corresponding to absorption maxima (Fig 70

2a) at 443 nm for 12+ (Fig. 2b, B) and 2.61 eV at 475 nm for 24+

(Fig. 2b, D and E).

The binding of DNP-DEG was further characterised in D2O

using 1H-NMR spectroscopy (Fig. 3), whereby downfield shifts19

of the and protons of the bipyridinium recognition units were 75

observed along with the simultaneous upfield shifts of DNP-DEG

aromatic protons. This effect arises from aromatic -electron

shielding of the bipyridinium units and strongly suggests19a that

face-to-face - stacking25 of DNP-DEG with the bipyridinium

units has occurred. The NMR spectra taken during the titration of 80

12+ and 24+ with DNP-DEG (Fig. 3) suggest


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.




Fig. 3 Stacked 1H NMR spectra (300 MHz, D2O, 298 K) following the

titration of a 2102 M solution of 12+ (a) and a 1.4102 M solution of 24+

(b) with DNP-DEG. The observed upfield shifts of the signals

corresponding to the π-electron deficient bipyridinium head group

aromatic protons are a result of the donor-acceptor charge transfer 5

interactions with π-electron rich DNP-DEG.

Fig. 4 Stacked 1H NMR spectra (300 MHz, D2O, 298 K) following the

titration of a 1.4102 M solution of 24+ (b) with DNP-DEG illustrating

the downfield shifts of the signals for the DNP-DEG aromatic protons as 10

the concentration of DNP-DEG is increased. The observed downfield

shifts of the signals corresponding to the π-electron rich DNP-DEG

aromatic protons result from the growing donor-acceptor polar stacks

across the micellar surface as successively more DNP-DEG molecules

intercalate themselves between contiguous π-electron deficient 15

bipyridinium head groups.

that the binding of DNP-DEG to 12+ differs substantially from the

binding of DNP-DEG to 24+. Increasing the guest concentration

of a 2102 M solution of 12+ in D2O resulted in a consistent,

fairly linear change in ppm shifts for protons in both the host and 20

the guest. The two α proton peaks remain within 0.2 ppm of one

another as the DNP-DEG concentration increases.

Increasing the guest concentration causes the β peaks to split,

however the peak splitting never exceeds 0.2 ppm. This suggests

that DNP-DEG, when bound and intercalated between contiguous 25

molecules of 12+, resides centered between the bipyridinium

units. Furthermore, the consistent ppm shifts brought about by

changes in guest concentration suggest that a single binding

process is being observed between the host and the guest.

Changes in guest concentration produce gradual ppm shifts by 30

Fig. 5 Space filling molecular models of the proposed donor-acceptor

stacking interactions between DNP-DEG and 12+ (a) and 24+(b) at the

micellar-water interface. Hydrogen atoms have been omitted for clarity.

virtue of shifting the thermodynamic equilibrium of the binding

process toward the host-guest complexation. Contradistinctively, 35

the spectra obtained from titrating 24+ with DNP-DEG in D2O

(Fig. 3b) reveal the presence of two distinct binding processes.24

Upon addition of DNP-DEG, the ppm shifts of the signals

corresponding to the protons adjacent to the nitrogens which

have been alkylated by the undecylenic tail increase abruptly, as 40

do the signals of the protons. However, once the sample

contains equal concentrations of host and guest, the rate of

change for these ppm shifts slows. For example, the signals for

the -xylyl aromatic protons shift from 7.65 ppm to 8 ppm as the

ratio of 24+ to DNP-DEG increases from 1:0 to 1:1, but as that 45

ratio increases from 1:1 to 1:2, the signals only shift from 8 ppm

to 8.05 ppm. This change in behavior suggests a transition in the

binding interactions between the DNP-DEG and the bipyridinium

units of 24+ where first and foremost the DNP-DEG engages

the bipyridinium units intramolecularly, where it is nestled in the 50

pocket of 24+, followed by intermolecular “alongside” binding

interactions as the ratio of host to guest increases. Evidence for

this binding sequence is also supported by the shifts of the signals

corresponding to the aromatic protons of DNP-DEG (Fig. 4).

Initially the signals for aromatic protons H3/7, H4/8, and H2/6 55

experience a classical19,24 upfield shift upon complexation with

24+. As the ratio of host to guest increases, these protons suddenly

start to experience dramatic downfield shifts as each bipyridinium

unit now starts to engage in binding interactions with two

molecules of DNP-DEG one in which DNP-DEG resides 60

within the pocket of 24+ and the second in which DNP-DEG

resides between contiguous molecules of 24+ serving as

intermolecular “glue” further stabilising the micellar aggregate.


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.




Fig. 6 The graphical representations of the Langmuir film packing at the air-water interface for 12+ and the corresponding Langmuir surface pressure ()

in the absence of DNP-DEG (a) and the increased Langmuir film packing density of 12+ upon addition of 1 molar equivalent of DNP-DEG and the

corresponding . Variable concentration surface tension plots for both processes (center) and the calculated taken at 298 K in H2O

Notably, while the signals for the different α protons of 5

12+experienced similar shielding effects with the addition of

guest, the signals for the different protons of 24+ experienced

very different shielding changes. The signals for the protons

adjacent to the nitrogens bound to the alkyl tails experienced

shifts from 9.15 ppm to 8.7 ppm, while the signals for the 10

protons adjacent to the methylene -xylyl bridge shifted by only

0.1 ppm. This indicates that DNP-DEG, when bound to 24+,

resides closer to the hydrophobic core of the micelle and does not

sit perfectly centered between the bipyridinium units as with 12+.

As a result we further conclude that the aromatic protons of DNP-15

DEG do not engage in edge-to-face π-interactions with the

aromatic ring of the p-xylyl bridge as has been reported19,24 for

similar donor-acceptor systems in polar aprotic organic solvents.

In each case, the one-dimensional face-to-face packing model25

between the -electron deficient bipyridinium units with the -20

electron rich DNP-DEG is evident.

Effects of donor-acceptor templation on micellar self-

assembly

The addition of 1 molar equivalent of DNP-DEG to solution of

12+ and both 1 and 2 equivalents to solutions of 24+ produced a 25

substantial change in the micellar aggregation process as

determined by further ST (Fig. 6 and 7a), conductivity (Fig. 7

bd), dynamic light scattering (Fig. 9 and 10), and -potential

measurements. It is interesting to point out however that changes

observed for the CAC were more pronounced than those 30

measured for the lower concentration CMC where little change

was observed. The effects of template-directed micellar

aggregation on the CMC and CAC are summarised in Table 1.

The addition of 1 equivalent of template to a solution of 12+ was

sufficient enough to decrease the CAC by almost 66% from 29.80 35

1.0 mM to 10.2 1.0 mM with a concomitant increase in the

Langmuir surface pressure (Fig. 6) to 25.5 0.3 mN m-1

mirroring surface pressure levels measured (Fig. 7a) for 24+

both with and without DNP-DEG added. The data suggest that

DNP-DEG behaves as a molecular glue stitching together 40

molecules of 12+ such that 12+ no longer behaves as a linear single

chain amphiphile but rather exhibits under templation

conditions properties of a dual chained gemini surfactant.

Similarly the addition of 1equivalent of DNP-DEG to solutions of

24+ resulted in 39% decrease in the CAC from 9.0 1.0 mM to 45

5.5 1.0 mM (Fig. 7a). The addition of a second equivalent of

DNP-DEG to 24+ resulted in another net decrease in the CAC

albeit not as significant as the change observed upon the addition

of the first equivalent. In neither case did the addition of DNP-

DEG affect the maximum reduction in surface tension for 24+ 50

(Fig. 7a), thus no significant changes in the Langmuir surface

pressure were measured.

Fig. 7 (a) Variable-concentration surface tension plots measured in H2O

at 298 K illustrating the CAC and the average Langmuir surface pressure

() for 24+ (red) with 1 equivalent of DNP-DEG (black) and 2 equivalents 55

of DNP-DEG (blue) added. Variable-concentration conductivity plots

measured in H2O at 298 K illustrating the CAC for 24+ (b) with 1

equivalent of DNP-DEG (c) and 2 equivalents of DNP-DEG (d) added.

Dynamic light scattering (DLS) and -potential measurements

confirmed that template-directed micellisation results in 60

significant increases in the size and stability of the aggregate

structures. For a 10 mM solution of 12+ an average hydrodynamic

diameter (DH) of 93 3 nm was measured and augmented upon

the addition of 1 equivalent DNP-DEG to 174 3 nm


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.




Fig. 8 Hydrodynamic diameter (DH) distributions measured for a 1102

M aqueous solution of 12+ (a) with 1 equivalent of DNP-DEG (b) added

using dynamic laser light scattering at 298 K.

(Fig. 8) with a concomitant increase in the -potential from 21.0

6.3 mV to 33.6 7.6 mV. 24+ at 5 mM experienced much more 5

substantial total gains in aggregate size from 112 19 nm to 279

37 nm (Fig. 9) with a simultaneous increase in the -potential

from 17.3 0.4 mV to 35.8 1.1 mV following the addition of 2

equivalents of DNP-DEG. The addition of DNP-DEG to the

detergent solutions also dramatically increased the hydrodynamic 10

size distribution of the aggregate structures. We believe that this

marked increase in the aggregate polydispersity supports our

hypothesis that cylindrical-type species6,8,15,17 with larger

length/diameter ratios are perhaps being formed in which

aggregates of various lengths are responsible for the overall size 15

distribution. In each case the addition of DNP-DEG resulted in -

potentials greater than 30 mV indicating that molecular

templation at the micellar-solvent interface results in an increase

of the colloidal stability of these solutions.

Templation effects on the free energy of micellisation (GM) 20

By employing a phase separation model13 which takes into

account the degree of counter ion binding to the micellar

aggregates, GoM per hydrophobic tail was calculated for both the

CMC and the CAC for 12+ and 24+ in the presence of the DNP-

DEG template and without. Comparing the Gibbs free energies 25

(G M) for analogous micellisations (Table 1) of the gemini and

single tailed surfactants reveals a consistent trend: that while the

magnitude of GM changes per molecule of the gemini

surfactant 24+ exceeds the GM per single tailed surfactant

molecule 12+ for each different micellisation process, the GM 30

per tail of the gemini surfactant is always smaller than the single

tailed surfactant’s GM per tail, except where molecular

Fig. 9 Hydrodynamic diameter (DH) distributions measured for a 5103

M aqueous solution of 24+ (a) with 1 equivalent of DNP-DEG (b) and 2

equivalents of DNP-DEG (c) added using dynamic laser light scattering at 35

298 K.

templation by DNP-DEG becomes more pronounced. This would

be the expected result if the micelles formed by both surfactants

are fundamentally similar and the principal contribution of the

covalent connection between the two halves of the gemini 40

surfactant is to effectively preorganise two surfactant monomers

into dimers. The GM per tail of the gemini surfactant is smaller

than the per tail GM of the single tailed surfactant because the

gemini surfactant’s micellisation process is already under way if

we consider the dimeric gemini surfactant as having been 45

covalently preorganised at the p-xylyl bridge. When the single

tailed surfactant forms into micelles, many surfactant molecules

come together to form structures that minimise interaction

between the hydrophobic tails and water molecules, an

entropically driven process. The inclusion of each new surfactant 50

molecule arguably makes some small contribution to the total

GM. The micellisation of the gemini surfactant 24+ has a

smaller total GM because there is no contribution to the total


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.




Fig. 10 Graphical representation of the effects of donor-acceptor templation on the micellar self-assembly of 12+ and 24+ and the Gibbs free energy of

micellisation (GM) for both the critical micelle concentration (CMC) and the critical aggregation concentration (CAC). Under templated conditions, it is

the second micellar transition, the CAC, occurring at higher concentrations rather than the CMC occurring at much lower concentrations that is affected

the most by the addition of DNP-DEG. Favourable decreases in GM for the CAC exceed 1 kcal mol1 whereas favourable decreases in GM for the 5

CMC do not exceed 1 kcal mol1. See Table 1.

10

Species CMCa

[mM]

GM CMCb

[kcal mol1]

CACa

[mM]

CACc

[mM]

GM CACb

[kcal mol1]

d

[mN m1]

DHe

[nm]

-Potentialf

[mV]

12+ 2.73 0.24 4.15 0.08 22.3 7.8 29.8 2.0 3.35 0.33 15.7 0.3 93 3 21.0 6.8

12+ + 1eq DNP-DEG 2.31 0.32 4.20 0.11 ---------- 10.2 1.0 4.51 0.54 25.5 0.3 174 3 33.6 7.6

24+ 2.77 0.15 3.13 0.15 8.2 1.4 9.0 1.0 3.27 0.13 27.8 0.8 112 19 17.3 0.4 24+ + 1eq DNP-DEG 1.67 0.18 4.00 0.12 5.9 0.3 5.5 1.0 4.69 0.07 27.4 0.5 158 5 35.0 4.5

24+ + 2eq DNP-DEG 1.61 0.23 3.82 0.15 4.9 0.7 4.5 1.0 5.02 0.10 26.9 0.4 279 37 35.8 1.1

a Obtained by variable-concentration conductivity measurements. b Obtained by the method described by Zana.13 The values represent the free energy of

transferring over a single hydrophobic chain from water to the micellar pseudophase. For the purposes of comparison, the free energies reported here for

the two-tailed gemini surfactant 24+ are for a single chain transfer. Doubling the GM for compound 24+ will yield a more accurate measure for the whole

molecule. c Obtained by variable-concentration surface tension measurements using the Du Noüy ring method. Only the 2nd critical micelle concentration

occurring at higher concentrations was observed using this method d Determined by Du Noüy ring method using equation = γo γCMC where γo is the 15

surface tension of water at 298 K and γCMC is the surface tension for the detergent solution at the critical micelle concentration. e Obtained using dynamic

laser light scattering. f Obtained using laser Doppler electrophoresis.

GM from the joining of two free monomers for the gemini

surfactant, the “monomers” are already joined by the -xylyl

bridge between the two halves of the molecule. It can also be 20

observed (Table 1, Fig. 10) that the effects of molecular donor-

acceptor templation on GM become more pronounced for the

CAC transition occurring at higher concentrations. This suggests

that the 2nd transition leads to micellar aggregate structures with a

larger length-to-diameter ratio (e.g., oblate or cylindrical type 25

species) for which face-to-face π-stacking interactions between

the π-electron deficient bipyridinium surfactant head groups and

DNP-DEG are more favoured.

Conclusions

In summary we have developed a model detergent binary blend in 30

which the surface activity and the CAC of two bipyridinium-

based amphiphiles can be modulated causing self-assembly to

occur at significantly lower surfactant concentrations by

Table 1 Critical Micelle Concentrations of 12+ and 24+ for the 1st and 2nd Transitions and the Corresponding Changes in Gibb’s Free Energies of

Micellisation (GM), Langmuir Surface Pressure (), Hydrodynamic Diameter (DH), and -Potential in the Presence and Absence of DNP-DEG in Water

at 298 K


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.




employing the principles of preorganisation and template-directed

self-assembly in aqueous solutions. We have also demonstrated

rather unexpectedly that linear single hydrophobic tailed

detergent molecules under templation conditions behave as

double-tailed phospholipid-like gemini surfactants. That is to say 5

that the monomeric surfactants in this study experienced a

significant enhancement in their efficiency and effectiveness in

reducing the surface tension of water mirroring the efficiency

and effectiveness of the dimeric gemini species upon donor-

acceptor templation. The experimental results further suggest that 10

template-directed self-assembly at the micellar-solvent interface

cannot augment to any large extent, detergent efficiency or

effectiveness at lowering the surface tension of water and the

onset of the CMC/CAC, until the possibility for long range -

stacking cooperativity along the air-water interface and across 15

larger micellar superstructures is established at concentrations

well above the first CMC. This leads us to believe that the native

micellar aggregate geometry plays a tremendous role in whether

or not the addition of -electron rich molecular templates will

result in a more favourable GoM. These findings auger well for 20

the future development of programmable and switchable

detergent blends based on donor-acceptor interactions in aqueous

environments.

Acknowledgements

This research is supported by a Welch Foundation Departmental 25

Grant (BT-0041), a Texas A&M University Corpus Christi

research grant, and a grant from the Texas Research Development

Fund. C. M. H. and M. S. M gratefully acknowledge the support

of an NSF Louis Stokes Alliances for Minority Participation

(LSAMP) grant (0703290). 30

Notes and references

Department of Physical & Environmental Sciences, Texas A&M

University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, Texas

78412-5774, United States

E-mail: [email protected] 35

† Electronic Supplementary Information (ESI) available: [1H and 13C and 1H-1H g-DQF-COSY spectra of compounds 12+ and 24+]. See

DOI: 10.1039/b000000x/

‡ Footnotes should appear here. These might include comments relevant

to but not central to the matter under discussion, limited experimental and 40

spectral data, and crystallographic data.

1 J.M. Lehn, Angew. Chem. Int. Ed., 2013, 52, 27.

2 (a) S.H. Yu and F. Possmayer, J. Lipid. Res., 1998, 39, 5555568;

(b) S.H. Yu, F. X. McCormack, D. R. Voelker and F. Possmayer, J.

Lipid Res., 1999, 40, 920929; (c) H. Fujioka, D. Halpern and D. P. 45

Gaver III, J. Biomech., 2013, 46, 319328.

3 M. A. Olson, A. B. Braunschweig, T. Ikeda, L. Fang, A. Trabolsi, A.

M. Z. Slawin, S. I. Khan and J. F. Stoddart, Org. Biomol. Chem.,

2009, 7, 43914405.

4 For examples of switchable detergent, amphipile and micellar 50

systems see: (a) H. Sakai, H. Imamura, Y. Kondo, N. Yoshino and M.

Abe, Colloids and Surfaces A: Physiochem. Eng. Aspects, 2004, 232,

221228; (b) A. F. Dexter, A. S. Malcolm, and A. P. J. Middelberg,

Nat. Mater., 2006, 5, 502506; (c) A. S. Malcolm, A. F. Dexter and

A. P. J. Middelberg, Asia-Pac. J. Chem. Eng., 2007, 2, 362367; (d) 55

S. Silvi, A. Arduini, A. Pochini, A. Secchi, M. Tomasulo, F. M.

Raymo, M. Baroncini and A. Credi, J. Am. Chem. Soc., 2007, 129,

1337813379; (e) I. Lagzi, D. Wang, B. Kowalczyk and B. A.

Grzybowski, Langmuir, 2010, 26, 1377013772; (f) H. Jin, Y. Zheng,

Y. Liu, H. Cheng, Y. Zhou and D. Yan, Angew. Chem. Int. Ed., 2011, 60

50, 1035210356; (g) L. Sambe, F. Stoffelbach, J. Lyskawa, F.

Delattre, D. Fournier, L. Bouteiller, B. Charleux, G. Cooke and P.

Woisel, Macromolecules, 2011, 44, 65326538; (h) K. Liu, Y. Yao,

C. Wang, Y. Liu, Z. Li and X. Zhang, Chem. Eur. J., 2012, 18,

86228628; (i) Q. Zhang, G. Yu, W.J. Wang, H. Yuan, B.G. Li 65

and S. Zhu, Langmuir, 2012, 28, 59405946.

5 (a) R. Nagarajan and E. Ruckenstein, Langmuir, 1991, 7, 29342969;

(b) T. A. Camesano and R. Nagarajan, Colloid Surface A, 2000, 167,

165177; (c) B. C. Stephenson, A. Goldsipe, K. J. Beers and D.

Blankschtein, J. Phys. Chem. B, 2007, 111, 10251044. 70

6 (a) C. Wang, Y. Guo, Y. Wang, H. Xu, R. Wang and X. Zhang,

Angew. Chem. Int. Ed., 2009, 48, 89628965; (b) K. V. Rao, K.

Jayaramulu, T. K. Maji and S. J. George, Angew. Chem. Int. Ed.,

2010, 49, 42184222; (c) C. Wang, Y. Guo, Z. Wang and X. Zhang,

Langmuir, 2010, 26, 1450914511. 75

7 G. Barin, R. S. Forgan and J. F. Stoddart, Proc. R. Soc. A., 2012, 468,

28492880.

8 Y. J. Jeon, P. K. Bharadwaj, S. W. Choi, J. W. Lee and K. Kim,

Angew. Chem. Int. Ed., 2002, 41, 44744476.

9 K. Wang, D.S. Guo, X. Wang and Y. Liu, ACS Nano, 2011, 5, 80

28802894.

10 F. M. Menger and J. S. Keiper, Angew. Chem. Int. Ed., 2000, 39,

19061920.

11 D.J. Feng, X.Q. Li, X.Z. Wang, X.K. Jiang and Z.T. Li,

Tetrahedron, 2004, 60, 61376144. 85

12 M. Asakawa, W. Dehaen, G. L. L’abbe, S. Menzer, J. Nouwen, F. M.

Raymo, J. F. Stoddart and D. J. Williams, J. Org. Chem., 1996, 61,

95919595.

13 R. Zana, Langmuir, 1996, 12, 12081211.

14 Terminal alkenes were employed for later investigations into 90

polymerised micellar systems and to decrease the hydrophobicity of

the tail. See: B. Durairaj and F. D. Blum, J. Colloid Interface Sci.,

1985, 106, 561564.

15 Here we define detergent efficiency as the concentration required to

reach a given surface tension reduction. We define detergent 95

effectiveness as the maximum reduction in surface tension that is

obtainable. See: M. J. Rosen and J. T. Kunjappu, Surfactants and

Interfacial Phenomena, John Wiley & Sons, Inc., New Jersey, 2012.

16 For examples of surfactant systems which exhibit a second critical

micelle concentration see: (a) A. González-Pérez, J. Czapkiewicz, G. 100

Prieto and J. R. Rodríguez, Colloid Polym. Sci., 2003,

281,11911195; (b) A. González-Pérez, J. Czapkiewicz, J. M. Ruso

and J. R. Rodríguez, Colloid Polym. Sci., 2004, 282, 11691173; (c)

A. R. Katritzky, L. M. Pacureanu, S. H. Slavov, D. A. Dobchev, D.

O. Shah and M. Karelson, Comput. Chem. Eng., 2009, 33, 321332; 105

(d) A. P. Romani, A. E. Machado de Hora, N. Hioka, D. Severino, M.

S. Baptista, L. Codognoto, M. R. Rodrigues and H. P. M. de Oliveira,

J. Fluoresc., 2009, 19, 327332.

17 S. May and A. Ben-Shaul, J. Phys. Chem., 2001, 105, 630640

18 (a) P.A. Brugger, P. P. Infelta, A. M. Braun and M. Grätzel, J. Am. 110

Chem. Soc., 1981, 103, 320326; (b) M. Krieg, M.P. Pileni, A. M.

Braun and M. Grätzel, J. Colloid Interface Sci., 1981, 83, 209213;

(c) K. Yamamura, Y. Okada, S. Ono, K. Kominami and I. Tabushi,

Tetrahedron Lett., 1987, 28, 64756478; (d) A. Diaz, P. A. Quintela,

J. M. Schuette and A. E. Kaifer, J. Phys. Chem., 1988, 92, 115

35373542; (e) A. Diaz and A. E. Kaifer, J. Electroanal. Chem.,

1988, 249, 333338; (f) P. Anton, J. Heinze and A. Laschewsky,

Langmuir, 1993, 9, 7785; (g) D. K. Lee, Y. I. Kim, Y. S. Kwon and

Y. S. Kang, J. Phys. Chem. B, 1997, 101, 53195323; (h) R. J.

Alvarado, J. Mukherjee, E. J. Pacsial, D. Alexander and F. M. 120

Raymo, J. Phys. Chem. B, 2005, 109, 61646173; (i) E. Marotta, F.

Rastrelli and F. Saielli, J. Phys. Chem. B, 2008, 112, 1656616574;

(j) A. B. Bordyuh, Y. A. Garbovskiy, G. V. Klimusheva, S. A.

Bugaychuk, T. A. Mirnaya, G. G. Yaremchuk and A. P. Polishchuk,

Ukr. J. Phys., 2008, 53, 11671173; (k) L.L. Li, H. Sun, C.J. Fang, 125

Q. Yuan, L.D. Sun and C.H. Yan, Chem. Mater., 2009, 21,

45894597.

19 (a) M. Asakawa, W. Dehaen, G. L. L’abbe, S. Menzer, J. Nouwen, F.

M. Raymo, J. F. Stoddart and D. J. Williams, J. Org. Chem., 1996,

61, 95919595; (b) M. Venturi, S. Dumas, V. Balzani, J. Cao and J. 130

F. Stoddart, New J. Chem., 2004, 28, 10321037; (c) M. Bria, G.


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.




Cooke, A. Cooper, J. F. Garety, S. G. Hewage, M. Nutley, G. Rabani

and P. Woisel, Tetrahedron Lett., 2007, 48, 301304.

20 M. A. Olson, Y. Y. Botros and J. F. Stoddart, Pure Appl. Chem.,

2010, 82, 15691574.

21 M. A. Olson, A. Coskun, L. Fang, A. N. Basuray and J. F. Stoddart, 5

Angew. Chem. Int. Ed., 2010, 49, 31513156.

22 R. Klajn, M. A. Olson, P. J. Wesson, L. Fang, A. Coskun, A.

Trabolsi, J. F. Stoddart and B. A. Grzybowski, Nat. Chem., 2009, 1,

733738.

23 J. N. Israelachvili, D. J. Mitchell and B. W. Ninham, J. Chem. Soc., 10

Faraday Trans. 2, 1976, 72, 15251568.

24 For recent examples of supramolecular complexes between

bipyridinium groups and dihydroxynaphthalene groups in which

inside and alongside binding interactions have been characterised see:

(a) S. Basu, A. Coskun, D. C. Friedman, M. A. Olson, D. Benitez, E. 15

Tkachouk, G. Barin, J. Young, A. C. Fahrenbach, W. A. Goddard III

and J. F. Stoddart, Chem. Eur. J., 2011, 17, 21072119; (b) Z. Zhu,

H. Li, Z. Liu, J. Lei, H. Zhang, Y. Y. Botros, C. L. Stern, A. A.

Sarjeant, J. F. Stoddart and H. M. Colquhoun, Angew. Chem. Int. Ed.,

2012, 51, 72317235. 20

25 C. A. Hunter and J. K. M. Sanders, J. Am. Chem. Soc., 1990, 112,

55255534.


Org

anic

& B

iom

ole

cula

r C

hem

istr

y A

ccep

ted

Man

usc

rip

t

Publ

ishe

d on

08

Aug

ust 2

013.

Dow

nloa

ded

by U

nive

rsity

of

Haw

aii a

t Man

oa L

ibra

ry o

n 11

/08/

2013

13:

02:3

6.



Date post:	11-Dec-2016
Category:	Documents
Upload:	travis
View:	213 times
Download:	0 times

Template-directed self-assembly by way of molecular recognition at the micellar–solvent interface:...

Documents