52
BOOK OF ABSTRACTS AND PROGRAM
BOOK OF ABSTRACTS
AND
PROGRAM
Program
October 3rd 2018
08:30-09:30 Welcome and Registration 09:30-10:00 Opening and Greetings. Chairperson: Prof. Michael Zinigrad.
K1 Keynote lecture. Prof. Dan Schechtman, Technion. Quasi-Periodic Crystals – A Paradigm Shift in Crystallography
10:40-11:10 Coffee break Morning Session. Chairperson: Prof. Albert Pinhasov
O1 Prof. Peter Comba, Universität Heidelberg, Anorg-Chem. Inst. Coordinated and Free Radicals in Nonheme Iron Oxidation Reactions
O2 Prof. Bilha Fischer, Dept. Chem., Bar-Ilan U. A Quest for Biocompatible Zn(II)/Cu(II)-Chelators for Therapeutic Applications
O3 Prof. Sara Goldstein, Inst. Chem. The Hebrew University of Jerusalem, Unusual antioxidative activity of cyclic nitroxides and their reduced forms
O4 Prof. Itamar Willner, Inst. Chem. The Hebrew University of Jerusalem, Stimuli-Responsive Materials for Drug Delivery, Shape-Memory, Self-Healing and New Catalytic Materials
O5 Prof. Zeev Gross, Technion. Haifa. Tuning the Photophysical and Chemical Properties
of Metallocorroles
12:50-14:00 Lunch Afternoon Session. Chairperson: Dr. Israel Zilbermann
O6 Prof. David Milstein, Dept. of Org. Chem., Weizmann Inst. Sci., Sustainable Catalysis Based on Metal-Ligand Cooperation
O7 Prof. Alexander Sorokin, IRCELYON, CNRS, Lyon, France, Recent Developments of Catalytic Chemistry of N-Bridged Diiron Phthalocyanines
O8 Prof. Christian Schöneich, Dept Pharm Chem. U. of Kansas. Tungstates induce the chemical degradation of proteins: one- and two-electron oxidation reactions and significance for the development of biotherapeutics
O9 Prof. Ehud Pines, Dept of Chem. Ben Gurion U. How Efficiently Can Carbonic Acid Protonate Biological Bases?
O10 Prof. Helmut Schwarz, Technische U. Berlin, Single-Atom Catalyzed Redox Reactions in the CO/N2O Couple: A Combined Experimental/Computational Approach
16:05-17:05 Poster Session and Coffee Break
18:00 - 20:00 Reception and Dinner organized by Ariel U.
October 4th 2018
Morning Session. Chairperson: Prof. Moshe Kol
O11 Guo-Xin Jin - Fudan U., China, Organometallic Macrocycles, Cages and Their Application
O12 Prof. Reshef Tenne, Dept. of Mat. and Interfaces, Weizmann Inst. Sci., Synthesis and Properties of Nanotubes from “Misfit” Compounds
O13 Prof. Ira Weinstock, Dept. Chem, Ben-Gurion U., Polyoxometalate Complexes of Metal and Metal-Oxide Nanostructures
O14 Prof. Itzhak Mastai, Dept. Chem., Bar-Ilan U., Enantioselective Mesoporous Carbon Prepared by Carbonization of Chiral Ionic Liquids
10:55-11:15 Coffee Break Chairperson: Dr. Tomer Zidki
O15 Prof. Dirk M. Guldi, Dept. of Chem. and Pharm., Friedrich-Alexander-Universität Erlangen-Nürnberg. Up- and Down-Converting Photons in Molecular Singlet Fission Materials
O16 Prof. Rinaldo Poli, Lab. Chim. Coord. CNRS in Toulouse - France,ENSIASET, News on the Interaction of Carbon-Based Radicals with Copper
O17
Prof. Rudi van Eldik, Dept. Inorg. Chem. Fridrich-Alexander University Erlangen-Nurenberg and Dept. Inorg. Chem., Jagiellonian U. Application of High Pressure Pulse Radiolysis, Flash Photolysis and NMR Techniques in the Clarification of Inorganic Reaction Mechanisms
O18 Prof. Jonathan L. Sessler, Dept. Chem., The Univ. of Texas Austin. Texaphyrins as Drug Candidates: Life, Death, and Attempts at Resurrection
12:55-13:50 Lunch Afternoon Session. Chairman: Prof. Boris Tsukerblat
O19 Prof. Sason Shaik, Inst. Chem. The Hebrew University of Jerusalem, Oriented Electric Fields — New Effectors in Chemistry
O20 Prof. Siegfried Schindler, Inst. Inorg. Anal. Chem., Justus-Liebig-U. Gießen, Germany. Copper Complexes in Solution - Funny Things Can Happen
O21 Prof. Moris Eisen, Technion, Haifa, The Wonderful Catalytic World of the Organoactinides
15:05-15:55 Coffee Break Chairperson: Prof. Joseph Rabani
O22 Prof. Krzysztof Bobrowski, Dept. Rad. Chem. Tech. Inst Nuc Chem. Tech. Warsaw, Poland. Pulse Radiolysis Approach for Probing Interaction between N- and C-terminal Amino Acid Residues in Peptides Containing Oligoproline Bridges
O23 Prof. Alex Schechter, Ariel U., A New Look at Electrochemical Catalytic Reactions on a Nanometric Level
O24 Dr. Galia Maayan, Technion. Haifa. A Self-Assembled Cyclic Structure and Electrocatalytic Water Oxidation from a Copper(II)-Peptoid
17:00-17:30 Closing Remarks
18:00 - 20:00 Reception and Buffet Dinner organized by the Israel Chemical Society
Oral Presentations
October 3rd 2018
K1
QUASI-PERIODIC CRYSTALS – A PARADIGM SHIFT IN CRYSTALLOGRAPHY
D. Shechtman
Technion, Haifa, Israel and ISU, Ames, Iowa, USA
Crystallography has been one of the mature sciences. Over the years, the modern
science of crystallography that started by experimenting with x-ray diffraction from
crystals in 1912, has developed a major paradigm – that all crystals are ordered and
periodic. Indeed, this was the basis for the definition of “crystal” in textbooks of
crystallography and x-ray diffraction. Based upon a vast number of experimental data,
constantly improving research tools, and deepening theoretical understanding of the
structure of crystalline materials no revolution was anticipated in our understanding the
atomic order of solids.
However, such revolution did happen with the discovery of the Icosahedral phase, the
first quasi-periodic crystal (QC) in 1982, and its announcement in 1984 [1, 2]. QCs are
ordered materials, but their atomic order is quasiperiodic rather than periodic, enabling
formation of crystal symmetries, such as icosahedral symmetry, which cannot exist in
periodic materials. The discovery created deep cracks in this paradigm, but the
acceptance by the crystallographers' community of the new class of ordered crystals did
not happen in one day. In fact it took almost a decade for QC order to be accepted by
most crystallographers. The official stamp of approval came in a form of a new definition
of “Crystal” by the International Union of Crystallographers. The paradigm that all crystals
are periodic has thus been changed. It is clear now that although most crystals are
ordered and periodic, a good number of them are ordered and quasi-periodic.
While believers and nonbelievers were debating, a large volume of experimental and
theoretical studies was published, a result of a relentless effort of many groups around
the world. Quasi-periodic materials have developed into an exciting interdisciplinary
science.
This talk will outline the discovery of QCs and describe the important role of electron
microscopy as an enabling discovery tool.
[1] D. Shechtman, I. Blech, Met. Trans. 16A (June 1985) 1005-1012.
[2] D. Shechtman, I. Blech, D. Gratias, J.W. Cahn, Phys. Rev. Letters, Vol 53, No. 20 (1984)
1951-1953.
O1
Coordinated and free radicals in nonheme iron oxidation reactions
Peter Comba
Universität Heidelberg, Anorganisch-Chemisches Institut and Interdisciplinary Center for
Scientific Computing (IWR), Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
http://www.uni-heidelberg.de/comba-group
There are alternative interpretations of the Fenton reaction as an OH. radical or an FeIV=O (ferryl) based
process, high-valent metal-oxygen species may, depending on the metal center, alternatively be described
as M(n+1)+-oxo or Mn+-oxyl radical complexes, and substrate radicals formed after C-H abstraction by ferryl
centers may react via a rebound process to form alcohol (or halogenated) products or, after cage escape,
follow free radical pathways.1 With the extremely rigid bispidine ligands (tetra- and pentadentate
diazaadamantane derivatives), we have thoroughly studied C-H abstraction, halogenation and oxygen
atom transfer reactions.2 Novel active intermediates, various alternative pathways and novel reactions
and reaction channels will be presented on the basis of experimental and computational data, and the
involvement of radical processes, the implication of cage escape and the importance of the spin state and
driving force will be discussed.
1 Comba, P.; Kerscher, M.; Krause, T.; Schöler, H. F. Env. Chem. 2015, 12, 381-395. 2 Comba, P.; Kerscher, M.; Schiek, W. Progr. Inorg. Chem., 2007, 55, 613-704.
O2
Prof. Bilha Fischer, Dept. Chem., Bar-Ilan U. A Quest for Biocompatible Zn(II)/Cu(II)-Chelators for
Therapeutic Applications
O3
Unusual antioxidative activity of cyclic nitroxides and their reduced forms
Sara Goldsteina, Eric Maimonb, Amram Samunic
a Institute of Chemistry, The Accelerator Laboratory, the Hebrew University of Jerusalem, Jerusalem
91904, Israel; b Nuclear Research Centre Negev, Beer Sheva, Israel; cInstitute of Medical Research Israel-
Canada, Medical School, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
The ever-increasing understanding of the involvement of radicals in diverse physiological
and pathological processes has expanded the search for compounds that can diminish radical-
induced damage. Stable cyclic nitroxide radicals are efficient radical scavengers that demonstrate
unique antioxidative activities. Common antioxidants are progressively depleted under oxidative
stress yielding secondary radicals, which might be more toxic than the primary ones. In contrast,
nitroxide reactions with radicals yield the respective oxoammonium cation, which is readily
reduced back in the tissue to the nitroxide thus continuously being recycled.
N OH
e-
e-N O.N=O+
hydroxylamine
nitroxide oxoammonium cation
H+ 2e-
Reduction of nitroxides to hydroxylamines occurs in vivo, which apparently might limit their
application. However, cyclic hydroxylamines are efficient H-atom donors detoxifying radicals
such as CO3•–, •OH and peroxyl radicals. Their protective effects can be similar to those of other
H-atom donors such as thiols and ascorbic acid. We show that cyclic hydroxylamines are superior
over these common antioxidants since the latter are depleted during the “repair” process, which in
some cases is also accompanied by consumption of oxygen. In contrast, cyclic hydroxylamines
not only donate H-atom, but this reaction yields their respective nitroxides, which are efficient
catalytic antioxidants.
O4
Stimuli-Responsive Materials for Drug Delivery, Shape-Memory, Self-Healing
and New Catalytic Materials
Itamar Willner
Institute of Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
E-mail: [email protected]
Stimuli-responsive “Smart” materials attract growing scientific interest due to their broad
potential applications.
Two kinds of stimuli-responsive “smart” materials will be introduced: (i) Stimuli-responsive
hydrogels, and particularly, nucleic acid-based stimuli-responsive hydrogels, will be discussed. The
signal-triggered reversible hydrogel-liquid transitions will be demonstrated. In addition, hybrid hydrogels
crosslinked by two or three stimuli-responsive bridges will be described. The signal-triggered reversible
transitions of the hydrogels across matrices of controlled stiffness will be presented using pH, ions, redox
agents and photochemical signals to control the hydrogel’s stiffness properties. The application of the
hydrogels as shape-memory and self-healing matrices, the use of the hydrogels as “mechanical devices”
and as switchable catalytic matrices, will be discussed. (ii) Metal-organic framework nanoparticles
(NMOFs) represent a broad class of highly porous materials. The synthesis of stimuli-responsive drug-
loaded NMOFs, and particularly, nucleic acid-modified NMOFs, will be described. The unlocking of the
NMOFs by different auxiliary signals, such as pH, aptamer-ligand complexes and DNAzymes will be
described. The controlled release of drugs and the targeted cytotoxicity of the drugs will be discussed. In
addition, programmed integration of proteins into the NMOFs will be presented, and the application of
the NMOFs in nanomedicine (sense-and-treat systems) and in programmed catalysis and photocatalysis
will be discussed.
O5
O6
Sustainable Catalysis Based on Metal-ligand Cooperation
David Milstein
Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel
The design of ”green” synthetic methodology and new approaches to sustainable energy are major goals of modern catalysis. Traditionally, catalysis by metal complexes has been based on the reactivity of the metal center, while the ligands bound to it influence its reactivity, but do not interact directly with the substrate. In a major advance in homogeneous catalysis, complexes based on “cooperating” ligands were developed, in which both the metal and a ligand undergo bond making and breaking in key steps of the catalytic cycle, thus providing exciting opportunities for catalytic design.
We have developed a new mode of metal-ligand cooperation, involving ligand aromatization – dearomatization, which provides a new approach to the activation of chemical bonds. Pincer-type complexes of several transition metals exhibit such cooperation, including complexes of Ru, Fe, Co, Rh, Ir, Ni, Pd, Pt, Mn and Re. This has led to fundamentally new, environmentally benign catalytic reactions, including several reactions which either produce dihydrogen or consume it. Synthetic and energy-related applications based on these reactions will be described.
O7
Recent developments of catalytic chemistry of
N-bridged diiron phthalocyanines.
Alexander B. SOROKIN
E-mail：[email protected]
Institut de Recherches sur la Catalyse et l’Environnement de Lyon, IRCELYON, CNRS – Université Lyon 1, 2 av. A. Einstein, 69626 Villeurbanne, France
While mononuclear metal phthalocyanine and porphyrin complexes are widely used in many catalytic
applications and their catalytic chemistry is well-documented, their dimeric counterparts, in particular,
µ-nitrido diiron complexes have not been considered as catalysts until recently.
Quite unexpectedly, these single-atom bridged diiron complexes are capable of reacting with oxidants
to form ultra high-valent diiron species. These short-living species were detected and characterized
by UV-vis, EPR, ESI-MS, Fe K edge EXAFS, XANES and Mössbauer techniques [1]. Of particular
interest are the unusual catalytic properties of these highly electrophilic species which are able to
oxidize methane [2] and to perform oxidative transformation of the aromatic C-F bonds [3].
All these catalytic reactions can be efficiently performed under mild and clean conditions using H2O2
oxidant. µ-Nitrido diiron species show the same mechanistic features as enzymes but exhibit
unprecedented reactivity. Advanced spectroscopic, labelling and reactivity studies confirm the
involvement of high-valent diiron oxo species in these catalytic reactions.
Current challenge in bio-inspired catalysis is the development of efficient catalysts readily accessible
on a large scale. In this context, N-bridged diiron phthalocyanine complexes seem to be promising
candidates combining availability and high reactivity in many reactions. They show a new unexpected
reactivity and provide a novel promising approach to challenging catalytic transformations under mild
and clean conditions. Mechanistic issues of their unusual reactivity are discussed.
1. P. Afanasiev, A. B. Sorokin, Acc. Chem. Res. 2016, 49, 583-593. 2. a) E. V. Kudrik, P. Afanasiev, L. X. Alvarez, P. Dubourdeaux, M. Clémancey, J.-M. Latour, G. Blondin, D. Bouchu, F. Albrieux, S. E. Nefedov, A. B. Sorokin, Nat. Chem. 2012, 4, 1024-1029. b) U. Isci, A.S. Faponle, P. Afanasiev, F. Albrieux, V. Briois, V. Ahsen, F. Dumoulin, A.B. Sorokin, S.P. de Visser, Chem. Sci. 2015, 6, 5063-5075. 3. C. Colomban, E. V. Kudrik, P. Afanasiev, A. B. Sorokin, J. Am. Chem. Soc. 2014, 136, 11321-11330.
O8
Tungstates induce the chemical degradation of proteins: one- and two-electron oxidation reactions
and significance for the development of biotherapeutics
Christian Schöneich
Department of Pharmaceutical Chemistry The University of Kansas Lawrence, KS 66047 USA Tungstate contaminations have been detected in glass pre-filled syringes, and have been correlated with the physical degradation of proteins as well as with immunogenic effects of protein therapeutics. Here, we show that tungstate-derived species can efficiently induce the rather selective chemical degradation of proteins when present at levels down to a few ppm. These reactions can be initiated thermally or photo-chemically, including through visible light, and include the intermediary generation of peroxotungstates. Evidence for the oxidation of both disulfides and backbone functional groups was obtained by several analytical techniques including SDS-PAGE and HPLC-MS/MS. Product analysis and mechanistic studies suggest the occurrence of both one- and two-electron oxidation pathways leading to very efficient fragmentation of proteins as large as monoclonal antibodies. The latter belong to an ever growing class of biotherapeutics implying that tungstate-induced chemical protein degradation reactions may pose a significant problem for the development of stable biotherapeutic formulations.
O9
How Efficiently Can Carbonic Acid Protonate Biological Bases?
Ehud Pines
Department of Chemistry, Ben-Gurion University of the Negev, POB 653, Ber Sheeva 84105, Israel.
E-mail: [email protected]
This study aimed to determine whether Carbonic Acid’s (H2CO3, CA) instability in respect to its
decomposition products H2O and CO2 compromises – as has usually been thought – its chemical reactivity as a
moderately strong Brønsted acid of considerable protonation ability. The relevance of this issue lies in
protonation processes in the blood plasma. Maintenance of large fluxes of protons is absolutely vital to sustain
life processes but this requirement does not appear to be consistent with the diminished concentration and
reduced diffusivity of the hydrated proton in the blood: The very low concentration of the traditionally assumed
protonating agent aqueous H+ ([H+]aq), is only about 40 nM in the blood plasma [1]. This feature and the proton’s
reduced diffusion coefficient in many hydrophobic or crowded biological environments render [H+]aq
kinetically insufficient both for rapid protonation of bases needed to sustain fast physiological processes and
for creating large proton fluxes necessary for very efficient metabolic processes. This ‘kinetic deficiency’ of the
physiological hydrated proton thus poses a central physiological problem. Indeed, the problem has been
recognized for many years and is often approached by invoking the existence of (often unspecified) fixed and
mobile buffers [2]. We have argued that CA (and not the proton) is the key protonating agent here, i.e., the
physiological problem is resolved by taking into account the protonation ability in the blood of CA, whose
concentration in the blood plasma is about 80 times higher than that of [H+]aq . The validity of this argument
depends on the stability of CA while protonating bases.
In this study we were able to unequivocally demonstrate both experimentally and theoretically that, when
encountering a base, B, the intact CA ─ a carboxylic acid with a considerable acid strength, pKa = 3.5 [3, 4] ─
does not in fact break down to H2O and CO2 before protonating the base; instead it behaves as an ordinary
carboxylic acid exhibiting efficient protonation capabilities in accordance with its considerable acidity greater
than that of formic acid and lactic acid [4], and which can directly protonate physiological bases in the reaction
H2CO3 + B ⇌ HCO3- + H+B, thus supporting our argument for the importance of CA as protonating agent. This
pivotal conclusion is further supported by Car-Parrinello ab initio molecular dynamics calculations [5-7].
References
[1] R. F. Schmidt, G. Thews, Human Physiology. (Springer-Verlag: Berlin, 1980). [2] W. Junge, S. McLaughlin, “The Role of Fixed and Mobile Buffers in the Kinetics of Proton Movement,” Biochim. Biophys. Acta, Bioenerg.
890, 1 (1987).
[3] K. Adamczyk, M. Premont-Schwarz, D. Pines, E. Pines, E. T. J. Nibbering, “Real-Time Observation of Carbonic Acid Formation in Aqueous
Solution,” Science, 326 (5960), 1690 (2009).
[4] D. Pines, J. Ditkovich, T. Mukra, Y. Miller, P. M. Kiefer, S. Daschakraborty, J. T. Hynes, E. Pines, “How Strong Is Carbonic Acid?”
[5] S. Daschakraborty, P. M. Kiefer, Y. Miller, Y. Motro, D. Pines, E. Pines, J. T. Hynes, “Reaction Mechanism for Direct Proton Transfer from Carbonic Acid to a Strong Base in Aqueous Solution I: Acid and Base Coordinate and Charge Dynamics,”J. Phys. Chem. B 120, 2271 (2016).
[6] S. Daschakraborty, P. M. Kiefer, Y. Miller, Y. Motro, D. Pines, E. Pines, J. T. Hynes, “Direct Proton Transfer from Carbonic Acid to a Strong
Base in Aqueous Solution Ii: Solvent Role in Reaction Path,” J. Phys. Chem. B 120, 2281 (2016).
[7] S. Daschakraborty, P. M. Kiefer, D. Pines, E. Pines, J. T. Hynes. Protonation of a Strong Base by Carbonic Acid in Aqueous Solution via One
Water Proton Relay. (In preparation).
O10
October 4th 2018
O11
Organometallic Macrocycles, Cages and Their Application
Guo-Xin Jin Department of Chemistry, Fudan University, Shanghai, 200433, P. R. China
E-mail address: [email protected]
The construction of new inorganic and organometallic macrocycles and cages with interesting structural features and
technologically useful functions have been topics of intense study with considerable potential.1 One of the chief
motivating factors to growth in this field is the development of new, functional and tunable donor building blocks that
can bridge transition metals. Ideal building blocks should be easily accessible, exhibit high affinities toward transition
metals, and possess facial coordination sites can undergo exchange reactions with various ligands. Half-sandwich
transition metal complexes (Cp*M, Cp* = 5-C5Me5) are useful model compounds in which one hemisphere of the
coordination shell is blocked by the voluminous Cp* rings. In the protected space below the Cp* ligands, various
bidentate or tridentate ligands can be accommodated.
Motivated by interest in supramolecular chemistry with organometallic half-sandwich complexes, we have initiated a
new approach for preparing organometallic macrocycles via C-H and B-H activations with Terephthalate and
dicarboxylate carborane.2 We report herein an efficient method for synthesizing molecular macrocycles of half-
sandwich iridium and rhodium complexes via C-H and B-H activation directed muticomponent self-assembly under mild
condition. 3
References:
1) a). Y.-F. Han, G.-X. Jin, Chem. Soc. Rev., 2014, 43, 2799; b). Y.-F. Han, G.-X. Jin, Accounts of Chemical Research 2014, 47, 3571; c). S. L.
Huang, T. S. A. Hor, G.-X. Jin, Coord. Chem. Rev., 2017, 333, 1-23.
2) a) Y. Lu, Y.-X. Deng, Y.-J. Lin, Y.-F. Han, L.-H. Weng, Z.-H. Li and, G.-X. Jin, Chem., 2017, 3, 110-121; b) W.-X. Gao, Y.-J. Lin, G.-X. Jin,
Dalton Trans., 2017, 46, 10498 - 10503; c). S-L. Huang, Y-J. Lin, T. S. A. Hor; G-X. Jin, J. Am. Chem. Soc., 2013, 135, 8125; d). S-L. Huang,
Y-J. Lin, Z-H. Li, G-X. Jin, Angew. Chem. Int. Ed., 2014, 53, 11218; e). L. Zhang, Y.-J. Lin, Z. Li, G.-X. Jin, J. Am. Chem. Soc., 2015, 137,
13670; e). W.-Y. Zhang, Y.-J. Lin, Y.-F. Han, G.-X. Jin, J. Am. Chem. Soc., 2016, 138, 10700.
3) a). H.-N. Zhang, W.-X. Gao, Y.-X. Deng, Y.-J. Lin, G-X. Jin, Chem. Comm, 2018, 54, 1559-1562; b). H. Li, Y-F. Han, Y-J. Lin, G.-X. Jin, J.
Am. Chem. Soc., 2014, 136, 2982; c). Y-F. Han, L. Zhang, L-H. Weng and G-X. Jin, J. Am. Chem. Soc., 2014, 136, 14608; d). Y-Y. Zhang, X-
Y. Shen, L-H. Weng, G-X. Jin, J. Am. Chem. Soc., 2014, 136, 15521; e). L. Zhang, L. Lin, D. Liu, Y.-J. Lin, Z.-H. Li, G.-X. Jin, J. Am. Chem.
Soc., 2017, 139, 1653-1660.
O12
Synthesis and properties of nanotubes from “misfit” compounds
R. Tenne, Department of Materials and Interfaces, Weizmann Institute, Rehovot 76100, Israel
Email: [email protected] web site: http://www.weizmann.ac.il/materials/tenne/
Misfit layered compounds (MLC) of the form (MX)1+yTX2 (M=Pb, Sn, rare earth, etc.; X=S,Se,Te;
T=Sn, Ta, V, etc.) are known since about 50 years and have been studied by various groups. They
are made of an alternating lattice made of one layer of a distorted cubic (orthorhombic) sublattice,
like PbS (MS), and hexagonal/octahedral lattice of, e.g. SnS2 or NbS2 (TS2) in a periodic
arrangement (denoted as MS-TS2 for brevity). Van der Waals forces hold the MX and TX2 layers
together, as well as polarization forces which emanate from partial charge transfer from the MX to
the TX2 units. Modern techniques allow synthesizing more complex superstructures from the MX
and TX2 sublattices. In many cases, the unit length of the two sublattices coincide along the
directions‐ b&c and is incommensurate along a. The lattice mismatch between the MX and TX2
sublattices is known to lead to the formation of microscopic cylindrical crystals for many years.
It was hypothesized that combining the lattice mismatch in the MX-TX2 misfit structure and the
general instability of nanocrystals from layered compounds, due to edge effects, will lead to
nanotubes (and also nanoscrolls) of small diameter (<300 nm) and high aspect ratio (>10).
Exploiting variety of solid‐state chemical techniques nanotubular structures from a large variety of
misfit compounds, like SnS‐SnS2; PbS‐NbS2 and LnS-TaS2 MLC were synthesized. Several CoO2-
based MLC tubes were synthesized and characterized as well. Their structure was studied mostly
via transmission electron microscopy as well as some DFT calculations. Raman analysis indicate
that the interlayer interactions are stronger in the tubular structures, compared with the bulk MLC.
Transport properties of single LaS-TaS2 tubes will be reported as well.
1. L. Panchakarla, B. Visic and R. Tenne, “Perspective”, J. Am. Chem. Soc. 2017, 139, 12865-12878.
O13
POLYOXOMETALATE COMPLEXES OF METAL AND METAL-OXIDE NANOSTRUCTURES
Ira A. Weinstock
Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva, 84105, Israel
Colloid science, and its more recent iteration as a branch of nanoscience, lies at the conceptual interface
between molecular systems and functional solid-state materials. Unlike molecules, most colloidal structures
are not amenable to characterization by single-crystal X-ray crystallography, while characterization of their
surface features (such as protecting-ligand domains) lies outside the scope of the crystallographic methods
used to define bulk phases of solid-state materials. However challenging, progress in this area nevertheless
requires a determined focus on structure and reactivity. One approach, demonstrated in the present talk, is
to use cryogenic transmission electron spectroscopy (cryo-TEM) to investigate soluble metal and metal-
oxide nanostructures stabilized by readily imaged (highly electron dense) polytungstate (POM) cluster-
anion ligands. The POM ligands simultaneously serve as "leaving groups" for controlling the
transformations of the metal-nanoparticle ligand shells, and guiding their self-assembly into supra-
structures capable of host-guest chemistry. A related topic is the use of POMs as covalently attached ligands
for reactive metal-oxide nanocrystals, giving a new class of nanostructures uniquely positioned between
molecular macroanions and traditional colloids. While molecular water-oxidation catalysts are remarkably
rapid, oxidative and hydrolytic processes in water can convert their active transition metals to colloidal
metal oxides or hydroxides that, while quite reactive, are insoluble or susceptible to precipitation. In
response, we demonstrate how oxidatively-inert ligands can be used to harness the metal oxides themselves.
With hematite iron-oxide as an example, this approach leads to an inherently stable, homogeneous water-
oxidation catalyst, capable of sustained operation for one week under turnover conditions, with no decrease
in activity, far exceeding the documented lifetimes of molecular catalysts under turnover conditions in
water. A final topic is the rational design of massive (>20,000,000 amu) soluble-coiled inorganic polymers
formed via oxo linkages between more than ten thousand bi-functional POM cluster-anion building blocks.
O14
Enantioselective mesoporous carbon prepared by carbonization of chiral ionic liquids.
Yitzhak Mastai1* Sapir Aloni1, Martin Oschatz2, and Nina Fechler2 1Dept. of Chemistry and the Institute of Nanotechnology Bar-Ilan University, Ramat-Gan, 52900 Israel.
2Max Planck Institute of Colloids and Interfaces, Dept. of Colloid Chemistry, Potsdam, Germany. E-mail: [email protected]
In recent years, chiral mesoporous1-3 materials have proven to play an important role in chiral chemistry. It is clear that mesoporous materials with different chiral functionalities have many advantages for applications in chiral chemistry such as chiral catalysts, surfaces for bio-recognition, and chiral separation processes.
In this lecture, we describe a novel and effective synthetic pathway for the preparation of
enantioselective mesoporous carbon, based on chiral ionic liquids (CILs) 4. CILs of amino acids are used as
precursors for the carbonization of chiral mesoporous carbon. The carbonization performed in a eutectic
salt melt to introduce adequate porosity to the final carbons. The morphology of the carbonized material
was investigated by high-resolution electron microscopy as shown in Figure 1 and reveal the formation of
carbon spherical particles of ca. 3 μm in size that consist of nanospheres of about nm with a surface area
of ca. 350 m2/g and an average pore size of 20 Å. We employ unique analytical techniques such as circular
dichroism spectroscopy, isothermal titration calorimetry (ITC Figure 2) and electrochemical techniques
(cyclic voltammetry Figure 3) in order to demonstrate the chiral nature of the mesoporous carbon. The
approach presented in this lecture is highly significant for the development of a new type of chiral
mesoporous materials for enantioselective chemistry.
a b c d
Fig. 1 (a and b) HR- TEM of the chiral mesoporous carbon (c) ITC heat of adsorption for D-and L-tartaric
acid solutions into CIL of L- Tyrosine (d) cyclic voltammetry if D-and L-tartaric acid onto mesoporous
carbon electrode of CIL of L- Tyrosine.
This work was supported by the German-Israeli Foundation for Scientific Research and Development (GIF).
(Grant No: I-1344-302.5/2016).
1) Marx, S.; Avnir, D., Accounts of Chemical Research 2007, 40, 768-776.
2) Gabashvili, A.; Medina, D. D.; Gedanken, A.; Mastai, Y. Journal of Physical Chemistry B 2007, 111, 11105-
11110.
3) Che, S.; Liu, Z.; Ohsuna, T.; Sakamoto, K.; Terasaki, O.; Tatsumi, T., Nature 2004, 429, 281.
4) Fuchs, I.; Fechler, N.; Antonietti, M.; Mastai, Y. Angew. Chem., Int. Ed. 2016, 55 408–412.
0 2 4 6 8 10 12 14 16 18-70000
-60000
-50000
-40000
-30000
-20000
-10000
0
cal m
ol-1
of in
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10 mM D/L-TA To Carbon L-Tyr
D-TA
L-TA
inj. #
-0.2 0.0 0.2 0.4 0.6 0.8
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
I/m
A
E/V vs. RHE
L-Tyr with L-TA
L-Tyr with D-TA
L-Tyr electrode with L/D -TA
O15
Up- and Down-converting Photons in Molecular Singlet Fission Materials
Dirk M. Guldi
aDepartment of Chemistry and Pharmacy & Interdisciplinary Center of Molecular Materials, Engineering
of Advanced Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058
Erlangen, Germany
The Shockley-Queisser limit places an upper bound on solar conversion efficiency for a single p-n junction
solar cell at slightly more than 30%. To surpass this limit, multi-exciton generation is being explored in
inorganic semiconductors, while singlet fission (SF) is being investigated in arrays of conjugated organic
molecules. In an optimal SF process, the lowest singlet excited state of one molecule (S1) that is positioned
next to a second molecule in its ground state (S0) is down-converted into two triplet excited states (T1)
each residing on one of the two adjacent molecules. The two triplet states initially form a correlated pair
state 1(T1T1), which then evolves into two separated triplet states (T1 + T1). As such, the energetic
requirement for SF is E(S1) ≥ 2 E(T1).
We have set our focus in recent years on intramolecular SF in molecular materials and their studies in
solution rather than on intermolecular SF investigations in crystalline films.
Implicit in intramolecular SF is a resonant, direct excitation of the SF material. In pentacene dimers linked
by a myriad of molecular spacers, SF takes place with quantum yields of up to 200%. In addition, all key
intermediates in the SF process, including the formation and decay of a quintet state that precedes formation
of the pentacene triplet excitons, have been identified. This approach is, however, limited to the part of the
solar spectrum, where, for example, the pentacene dimers feature a significant absorption cross-section. To
employ the remaining part of the solar spectrum necessitates non-resonant, indirect excitation of the SF
materials via either up- or down-conversion. For example, the up-conversion approach is realized with
singlet excited states in pentacene dimers, which are accessed by two-photon absorptions (TPA). TPA is
then followed in the second step of the sequence by an intramolecular SF – similar to what is seen upon
resonant, direct excitation. Quite different is the down-conversion approach, which is based on an
intramolecular Förster resonance energy transfer (FRET) and thereby the (photo)activation of the SF
material. FRET requires the use of a complementary absorbing chromophore and enables funneling its
excited state energy unidirectionally to the SF performing pentacene dimer. Again, SF completes the
reaction sequence.
O16
News on the Interaction between Carbon-based Radicals and Copper
Complexes
Thomas G. Ribelli,a Krzysztof Matyjaszewski,a Rinaldo Polib
aCarnegie Mellon University, Department of Chemistry, 4400 Fifth Ave, Pittsburgh, PA 15213,
USA
bLaboratoire de Chimie de Coordination, UPR CNRS 8241, 205 Route de Narbonne, 31077
Toulouse Cedex 4, France
The reaction between carbon-based radicals and copper(I) complexes yields thermally labile
organocopper(II) derivatives.1 These are of great relevance to, among other areas, copper-
mediated controlled radical polymerization. In particular, super-active atom transfer radical
polymerization (ATRP) catalysts have been shown to lead to catalyzed radical termination, an
unwanted phenomenon that seems specific for acrylate radicals and that interferes with controlled
chain growth.2 This reaction is likely taking place through organocopper(II) intermediates.3
Recent studies on the mechanism of the non-catalyzed and catalyzed termination of acrylate and
methacrylate radicals,4 coupled with mechanistic studies of the catalyzed radical termination,
have unveiled peculiar phenomena that suggest new reactivity pathways for organocopper(II)
complexes.
References
1 (a) A. Masarwa and D. Meyerstein, Adv. Inorg. Chem. 2004, 55, 271-313. (b) T. G. Ribelli, K. Matyjaszewski and R. Poli, J. Coord. Chem. accepted. 2 (a) K. Schröder, D. Konkolewicz, R. Poli and K. Matyjaszewski, Organometallics 2012, 31, 7994-7999. (b) Y. Wang, N. Soerensen, M. Zhong, H. Schroeder, M. Buback and K. Matyjaszewski, Macromolecules 2013, 46, 683-691. 3 T. G. Ribelli, S. M. W. Rahaman, J.-C. Daran, P. Krys, K. Matyjaszewski and R. Poli, Macomolecules 2016, 49, 7749–7757. 4 (a) T. G. Ribelli, K. F. Augustine, M. Fantin, P. Krys, R. Poli and K. Matyjaszewski, Macromolecules 2017, 50, 7920–7929. (b) T. G. Ribelli, S. M. W. Rahaman, K. Matyjaszewski and R. Poli, Chem. Eur. J. 2017, 23, 13879 – 13882.
O17
Application of high pressure pulse radiolysis, flash photolysis and NMR techniques in
the elucidation of inorganic reaction mechanisms
Rudi van Eldika,b
a Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, Egerlandstr. 1, 91058
Erlangen, Germany
b Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland
The presentation will consist of a historical account of the development of high pressure (HP)
techniques to follow fast chemical processes in solution as a function of hydrostatic pressure in
the range up to 200 MPa (i.e. 2 kbar) using pulse radiolysis, flash photolysis and NMR
instrumentation. Typical examples will be used to demonstrate the mechanistic insight that could
be gained from the application of these techniques in the study of inorganic (and bioinorganic)
reaction mechanisms. These will include:
Application of HP pulse radiolysis: 1
Water exchange and ligand substitution reactions on [Cr(H2O)6]2+
Application of HP flash photolysis: 2
Volume profiles for the binding of NO to CytP450cam and functional model porphyrins
Application of HP NMR: 3
Water exchange reactions on aquated first row transition metal ions in comparison to
similar reactions for their polyaminecarboxylate complexes
References
1. J.F. Wishart and R. van Eldik, Rev. Sci. Instrum., 63, 3224 (1992); R. van Eldik, W. Gaede, H. Cohen and D.
Meyerstein, Inorg. Chem., 31, 3695 (1992); W. Gaede, R. van Eldik, H. Cohen and D. Meyerstein, Inorg. Chem., 32,
1997 (1993); R. van Eldik and D. Meyerstein, Acc. Chem. Res., 33, 207 (2000).
2. A. Franke, G. Stochel, C. Jung and R. van Eldik, J. Am. Chem. Soc., 126, 4181 (2004); A. Franke, G. Stochel, N.
Suzuki, T. Higuchi, K. Okuzono and R. van Eldik, J. Am. Chem. Soc., 127, 5360 (2005); A. Franke, N. Hessenauer-
Ilicheva, D. Meyer, G. Stochel, W.-D. Woggon and R. van Eldik, J. Am. Chem. Soc., 128, 13611 (2006).
3. J. Maigut, R. Meier, A. Zahl and R. van Eldik, Inorg. Chem., 46, 5361 (2007); J. Maigut, R. Meier, A. Zahl and R. van
Eldik, Inorg. Chem., 47, 5702 (2008); J. Maigut, R. Meier and R. van Eldik, Inorg. Chem., 47, 6314 (2008); J. Maigut,
R. Meier, A. Zahl and R. van Eldik, J. Am. Chem. Soc., 130, 14556 (2008).
O18
“Texaphyrins as Drug Candidates: Life, Death, and Attempts at Resurrection”
Jonathan L. Sesslera,b
aDepartment of Chemistry, 105 E. 24th Street – A5300, The Univ. of Texas, Austin, TX
78712-1224 USA
bCenter for Supramolecular Chemistry and Catalysis, Shanghai University, Shanghai 200444, P. R. China
E-mail: [email protected]
Expanded porphyrin is a term we introduced into the literature in 1988 to describe larger
homologues of natural and synthetic tetrapyrrolic macrocycles. Expanded porphyrins,
along with many other contracted, isomeric, and core-modified porphyrin analogues, are
now known. Expanded porphyrins, in particular, have seen application in areas as diverse
as anion recognition and transport, self-assembly, liquid-liquid ion extraction,
photodynamic therapy, and anticancer drug development. In this lecture, a specific focus
will be placed on the first set of expanded porphyrins to act as metal complexing agents,
the so-called texaphyrins. Two of the texaphyrin complexes, known as MGd and MLu,
were the founding technology for Pharmacyclics, Inc., a company that later developed a
best-selling leukemia drug and was acquired by AbbVie for $21B in 2015. New work
exploiting lessons learned from the early days of Phamcyclics, Inc. and leading to the
founding of Cible, Inc. will then be described in detail. Some non-biomedical aspects of
expanded porphyrin chemistry, including recent collaborative work devoted to creating
so-called 3D aromatic molecules, will be presented as time permits.
This work has benefited from support from the U.S. National Science Foundation, The
National Institutes of Health, the Cancer Research and Prevention Institute of Texas, as
well as the R. A. Welch Foundation. Productive collaborations with a number of groups,
including those of Profs. Dongho Kim, Shunichi Fukuzumi, T.K. Chandrashekar,
Christophe Bucher, Dirk Guldi, Pradeepta Panda, Changhee Lee, Jan Jeppesen,
Masatoshi Ishida, and Tomas Torres, are also gratefully acknowledged.
Lead References
• Sessler, J. L.; Murai, T.; Lynch, V.; Cyr, M. J. Am. Chem. Soc. 1988, 110, 5586-5588.
• Ishida, M.; Kim, S.-J.; Preihs, C.; Ohkubo, K.; Lim, J. M.; Lee, B. S.; Park, J. S.; Lynch, V. M.; Roznyatovskiy, V. V.; Sarma, T.; Panda, P. K.; Lee, C. H.; Fukuzumi, S.; Kim, D.; Sessler, J. L. Nature Chem. 2013, 5, 15-20.
• Cha, W.-Y.; Kim, T.; Ghosh, A.; Zhang, Z.; Ke, X.-S.; Ali, R.; Lynch, V. M.; Jung, J.; Kim, W.; Lee, S.; Fukuzumi, S.; Park, J. S.; Sessler, J. L.; Chandrashekar, T. K.; Kim, D. “Bicyclic Baird-type Aromaticity,” Nature Chem. 2017, 9, 1243-1248.
Prof. Jonathan L. Sessler was born in Urbana, Illinois, USA on May 20, 1956. He received a B.S. degree (with Highest Honors) in chemistry in 1977 from the University of California, Berkeley. He obtained a Ph.D. in organic chemistry from Stanford University in 1982 (supervisor: Professor James P. Collman). He was a NSF-CNRS and NSF-NATO Postdoctoral Fellow with Professor Jean-Marie Lehn at L'Université Louis Pasteur de Strasbourg, France. He was then a JSPS Visiting Scientist in Professor Tabushi's group in Kyoto, Japan. In September, 1984 he accepted a position as Assistant Professor of Chemistry at the University of Texas at Austin, where he is currently the Doherty-Welch Chair. Dr. Sessler has authored or coauthored over 700 research publications, written two books (with Dr. Steven J. Weghorn and Drs. Philip A. Gale and Won-Seob Cho, respectively), edited two others (with Drs. Susan Doctrow, Tom McMurry, and Stephen J. Lippard, Placido Neri and Mei-Xiang Wang), and been an inventor of record on over 75 issued U.S. Patents. To date, Dr. Sessler’s work has been featured on more than 40 journal or book covers. His current H-index is 98. Dr. Sessler is an Associate Editor for ChemComm. Dr. Sessler is a co-founder (with Dr. Richard A. Miller) of Pharmacyclics, Inc., which was acquired by AbbVie for $21B in 2015. He is currently launching Cible, Inc. with Dr. Jonathan F. Arambula and Ms. Karen Strnad. Dr. Sessler has served as the co-organizer of several international conferences in porphyrin, supramolecular, and macrocyclic chemistry and numerous ACS symposia. In addition to English, he speaks French, Spanish, German, and Hebrew reasonably well and can get by in Japanese. He struggles with Korean. Dr. Sessler’s work has been recognized with several awards, including the ACS Cope Scholar Award, the RSC Centenary Prize, the Southwest Regional ACS Award, the Molecular Sensors-Molecular Logic Gates Award, the CASE award, and the Hans Fischer Award. He is a member of the U.S. National Academy of Inventors and was named Inventor of the Year at The Univ. of Texas at Austin in 2016. He was recently named the 2018 Thomas Dougherty awardee in Photodynamic Therapy.
Jonathan Sessler
O19
O20
Copper complexes in solution – Funny things can happen
Siegfried Schindler, Institute for Inorganic and Analytical Chemistry, Justus-Liebig-University Gießen,
Heinrich-Buff-Ring 17, 35392 Gießen, Germany
Abstract:
There is still high interest in selective oxidations of organic substrates using dioxygen (air) and a metal
complex as a catalyst. The holy grail in that kind of chemistry is selective oxidation of methane to
methanol as observed in nature for copper or iron based methane monooxygenases. However, often
chemistry follows more serendipity than allowing a rational design of suitable model compounds.
Typical for metal complexes a colorful surprise can allow more insight into these reactions. The
presentation will demonstrate that it is not always necessary to work with highly complex compounds to
achieve selective oxidations and how kinetic studies using low temperature stopped-flow techniques
can help to optimize reactions of this type.
O21
O22
Pulse Radiolysis Approach for Probing Interaction between
N- and C-terminal Amino Acid Residues
in Peptides Containing Oligoproline Bridges Krzysztof Bobrowski,1 Piotr Filipiak,2 Gordon L. Hug,3 Bronisław Marciniak,2 Dariusz
Pogocki,4 Christian Schöneich5
1
Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland 2
Faculty of Chemistry, Adam Mickiewicz University, 61-614 Poznan, Poland 3
Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, United States 4
Faculty of Biology and Agriculture, University of Rzeszów, 35-601 Rzeszów, Poland 5
School of Pharmacy, Department of Pharmaceutical Chemistry, University of Kansas, Lawrence,
Kansas, 66047, United States
The mechanism of the •OH-induced oxidation processes of Met-(Pro)n-Met peptides
that contain two methionine (Met) residues located on the N- and C-terminal and
separated by a defined number ( n = 0 – 4) of proline (Pro) residues was investigated
in aqueous solutions using pulse radiolysis. The use of such peptides allowed for
distance control between the sulfur atoms located in the side chains of Met residues.
The formation of a contact between the side chains of the Met residues was probed
by the observation of transients with σ*-type 2c-3e S∴S and S∴O bonds as well as
of α-(alkylthio)alkyl radicals (αS). This approach enabled the monitoring, in real time,
of the efficiency and kinetics of interactions between methionine side chains. The
yields of these transients (measured as G-values) were found to be dependent on
the number of Pro residues; however, they were not dependent in a simple way on
the average distance (rS-S) between the sulfur atoms in Met residues. A decrease in
the yield of the (S∴S)+ species with an increase in the number of Pro residues in the
bridge occurred at the expense of an increase in the yields of the intramolecular
three-electron-bonded (S∴O)+ radical cations and αS radicals. A detailed
understanding of these trends in the chemical yields was developed by modelling the
underlying chemical kinetics with Langevin dynamical simulations of the various
oligoproline peptide chains and combining them with a simple statistical mechanical
theory on the end-to-end contact rates for polymer chains. This analysis showed that
the formation of a contact between terminal Met residues in the peptides with 0 – 2
Pro residues was controlled by the activated formation of (S∴S)+ whereas in the
peptides with 3 and 4 Pro residues, by the relative diffusion of the sulfur radical cation
and unoxidized sulfur atom.
O23
A New Look at Electrochemical Catalytic Reactions on a Nanometric Level
Alex Schechter, Srikanth Kolagatla, Palaniappan Subramanian
Department of Chemical Sciences, Ariel University, Ariel 40700, Israel
A fundamental and detailed understanding of chemical and physical properties is essential for
improving electrocatalysts in general and for the study of oxygen reduction reaction (ORR) in
particular. We have developed and used Scanning Electrochemical Microscopy-Atomic Force
Microscopy (SECM-AFM) imaging technique that can provide high resolution detailed
electrochemical and spectral information of oxygen reduction reaction (ORR) reaction at a lateral
resolution of less than 50 nm. The ORR activity of an individual unsupported Pt nanoparticle,
carbon-supported Pt aggregates and Fe, N surface modified graphitic carbon was mapped under
selected reduction conditions. This newly developed method utilizes a gold coated SiO2 tip
imbedding a 50 nm diameter Pt electrode. The tip was positioned at a constant working distance of
~4-8 nm above the catalyst surface using force feedback control. A 532 nm Raman laser directed
to the apex of the tip was applied to collect tip enhanced Raman spectral (TERS) signal of the
reaction byproduct (H2O2). Thus, we simultaneously mapped the electrochemical oxygen
reduction by the Pt electrode and the H2O2 by the gold coating secondary electrode and at the same
time reordered the peroxide signal under the same scanned area. A direct evidence was seen,
showing for the first time that the same active ORR sites are also responsible for peroxide
formation. Moreover, on a nanometric level ORR proceed mostly via 2 electron reaction to
hydrogen peroxide rather than the literature reported 4 electrons reduction of O2 to water.
O24
A Self-Assembled Cyclic Structure and Electrocatalytic Water Oxidation
from a Copper(II)-Peptoid Galia Maayan
Schulich Faculty of Chemistry, Technion – Israel Institute of Technology, Haifa, Israel
Metal-binding peptoids and metallopeptoids are an important class of biomimetic oligomers with
demonstrated functionalities including folding,[1] selective recognition[2] and catalysis.[3-4] Here,
we will present the first example of metallopeptoid-based water oxidation electrocatalyst, a Cu-
peptoid trimer bearing a bipyridine and an –OH groups, which is both highly stable and efficient,
enabling oxygen evolution in aqueous phosphate buffer solution at pH 11.5. Based on
electrochemical experiments and DFT-D3 calculations we propose a unique intramolecular
cooperative catalytic mechanism for this reaction, which is suggested to have a major role in the
high stability of the complex. Attempts to characterize this complex in the solid-state, led to its
crystallization in acetonitrile. Surprisingly, its X-ray diffraction analysis revealed an exceptional,
highly symmetric, cyclic structure formed by the self-assembly of two peptoid molecules with
two Cu(II) ions. Replacing the hydroxyl group by either an –OCH3 or an –NH2 groups resulted in
the formation of the first examples of aqua-bridged dinuclear double-stranded peptoid helicates,
upon copper binding and crystallization (Fig. 1).[5] Spectroscopic and computational data showed
that these crystals were re-dissolved in acetonitrile, the macrocycles containing –OH and –OCH3
disassemble to their corresponding monometallic complexes, while the one containing the –NH2
side chain, having the largest amount of intermolecular hydrogen bonds, is stable in solution.[5]
Figure 1. Crystal structures of self-assembled cyclic metallopeptoids showing highly symmetric
macrocycle (right) and aqua-bridged (left) dimeric complexes, composed of two peptoid trimers
and two Cu2+ ions. The balls representation of the later describes the first dinuclear double-
stranded peptoid helicates.
References
[1] L. Zborovsky, A. Smolyakova, M. Baskin and G. Maayan, Chem. Eur. J., 2018, 24, 1159 –1167.
[2] M. Baskin, G. Maayan, Chem. Sci., 2016, 7, 2809-2820.
[3] Prathap, K. J.; Maayan, G. Chem. Commun. 2015, 51, 11096-11099.
[4] C. M. Darapanani, A. Sadhukha, G. Maayan, Journal of Catalysis 2017, 355, 139–144.
[5] T. Ghosh, N. Fridman, M. Kosa, G. Angew Chem. In press.
Poster Presentations
P1
Synthesis and biological studies of new multifunctional curcumin platforms for
anticancer drug delivery
Andrii Bazylevicha, Helena Tuchinskyd, Eti Zigman-Hoffmanb,
Ran Weissmanb,c,d , Ofer Shpilbergb,c,e , Oshrat Hershkovitz-Rokah b,c,d , Leonid Patsenkera,
Gary Gellermana; [email protected];
a Department of Chemical Sciences, Ariel University, Ariel, 40700, Israel; b Institute of Hematology,
Assuta Medical Centers, Tel Aviv, Israel; c Translational Research Lab, Assuta Medical Centers, Tel
Aviv, Israel; d Department of Molecular Biology, Faculty of Natural Sciences, Ariel University, Ariel,
Israel;
e Pre-Medicine Department, School of Health Sciences, Ariel University, Ariel, Israel.
A facile synthetic strategy towards the bioactive curcumin based platforms that are able to bear
and release anticancer drugs like amonafide and chlorambucil is reported. Each phenolic hydroxyl
or carboxyl groups of the platform can thus be covalently bound to an anticancer agent through a
biodegradable ester or carbamate bounds and conjugated to the given carrier for drug delivery. The
leading curcumin-based platform has presented antioxidant activity similarly to curcumin but
much potent cytotoxicity in vitro in agreement with the augmented blockage of NF-kB cell
survival pathway. Chemo- and biostability as well as drug release profiles of the synthesized
curcumin platforms with and without drugs correspondingly is discussed. The approach presented
here may prove beneficial for bioactive curcumin based delivery applications where multiple drug
delivery is required in a consecutive and controlled mode.
CURCUMIN
P2
Fluorescent Self-Healing Imine Carbon Dot Gels
Sagarika Bhattacharya, Raz Jelinek
†Department of Chemistry, Ben Gurion University of the Negev, Beer Sheva 84105, Israel. E-mail:
[email protected]; Fax: (+) 972-8-6472943 Ilse Katz Institute for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
Carbon dots (C-dots) are the one of the emerging class of photoluminescent nano material
which attracted substantial attraction due to their wide applicability in bioimaging, biosensing,
theranostics, photocatalysis, and as optoelectronic devices.1 One of the major drawbacks of C-dot
is their aggregation induced fluorescence quenching in solid state, due to collision among
themselves. To overcome the collision and to restrict the motion of the C-dots, they can be
immobilized inside supramolecular 3D network for preventing the aggregation induced solid state
emission. Supramolecular gels are flexible, soft material composed of various gelator molecules
and trap solvent inside their porous network. Previously, C-dot was immobilized in the various
types of supramolecular gel matrix and has been explored extensively in producing the hybrid
material with better performances.2 For the first time we synthesized and reported aldehyde
functionalized C-dots prepared from glutaraldehyde, benzaldehyde and a polymer of aldehyde.
The aldehyde groups on the surface of the C-dot were condensed with the primary amine groups
of the polyethylenimine (PEI) polymer and thus the organo-gelation was promoted. Moreover, due
to the presence of reversible imine bonds the PEI/C-dot organo gel display a unique self-healing
behavior without any external stimuli. Besides, the newly synthesized fluorescent PEI/C-dot gels
were also utilized to fabricate a white light emitting device by stacking the green and the yellow
gel films.
Figure 1. Schematic representation of PEI/C-dot gel
References: 1. Yuan, F.; Li, S.; Fan, Z.; Meng, X.; Fan, L.; Yang, S., Shining carbon dots: Synthesis and biomedical and
optoelectronic applications. Nano Today 2016, 11 (5), 565-586.
2. Bhattacharya, S.; Sarkar, R.; Nandi, S.; Porgador, A.; Jelinek, R., Detection of Reactive Oxygen Species by
a Carbon-Dot–Ascorbic Acid Hydrogel. Anal. Chem. 2017, 89 (1), 830-836.
Polyethylenimine Polyethylenimine/C-dot gel
P3
A chain mechanism for visible-light driven water Oxidation by
polyoxometalate complexes of hematite
Biswarup Chakraborty, Gal Gan-Or, Manoj Raula, and Ira A. Weinstock*
Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology,
Ben-Gurion University of the Negev, Israel Email: [email protected]
Abstract: An unprecedented role for metal-oxide cluster-anions (polyoxometalates, or POMs) as
covalently coordinated inorganic ligands for individual hematite nanocrystals, gives isolable
anionic clusters uniquely positioned between molecular macroanions and traditional colloidal
nanoparticles (Figure 1).[1] POM anions, α-XW11O39n- (X= PV, SiIV and AlII; n = 7-9) and α-
P2W17O6110- serve as pentadentate “capping” ligands for complexed Fe(III) ions linked via their
sixth coordination site to α-Fe2O3 cores. Different spectroscopic methods, electron microscopic
images and analytical measurements confirm the presence of POM-capping ligands, [α-
XW11O39Fe-O-]n-, [α-P2W17O61Fe-O-]n-, covalently bound to the surfaces of the 3-6 nm hematite
cores. On illumination with a visible light, the inherently stable POM-complexed α˗Fe2O3 NCs
oxidized water in presence of IO4- as sacrificial oxidant and operated for seven days with no loss
of activity (Figure 1). Indefinite stability of these unique complexes in water over a wide range of
pH values, led us to study the kinetics and mechanism of photochemical water oxidation. A detail
of Kinetic study with a plausible mechanism of water oxidation with the NCs will be presented.
Figure 1. Visible-light driven water oxidation by the α-Fe2O3-POM hybrid.
References:
[1] M. Raula, G. Gan Or, M. Saganovich, O. Zeiri, Y. Wang, M. R. Chierotti, R. Gobetto, I. A. Weinstock, Angew.
Chem. Int. Ed. 2015, 54, 12416-12421.
[2] B. Chakraborty, G. Gan Or, M. Raula, E. Gadot, I. A. Weinstock, Nat. Commun. 2018 (in revision)
P4
The nature of H5PV2Mo10O40 oxidants in strongly acidic solvents Chandan Kr. Tiwari, Mark Baranov and Prof. Ira A. Weinstock*
Department of Chemistry and Ilse Katz Institute for Nanoscale Science & Technology,
BenGurion University of the Negev, Beer-Sheva, Israel. E-mail: [email protected]
H5PV2Mo10O40 (1) polyoxometalate (POM) are electron transfer (ET) and electron transfer-
oxygen transfer (ET-OT) catalysts for selective oxidation of hydrocarbons. In many organic
solvents, the scope of these reactions was limited by the oxidation potential of 1, which is ca.
0.4-0.45 V versus saturated calomel electrode (SCE).1 Recently, however, Neumann found that in
50% H2SO4 the reduction potential of 1 was increased to 1.1 V versus SCE, and as a result, able
to oxidize C-H bonds of toluene2 and benzene to benzaldehyde and phenol respectively.3 To
better understand the nature of 1 in H2SO4, we (in collaboration with the Neumann group) have
been investigating the solution-state chemistry of 1 as a function of H2SO4 concentration. Recent
findings suggest that 1 rearranges in 50% H2SO4 so as to partially release V(V) (VO2+ in the
presence of H2SO4),4 and that this species might be responsible for the strongly oxidizing
properties of the system while the selectivity could be governed by in-situ formed
Isopolymolybdate. In cyclic voltammograms (CVs) of 1 in 50% H2SO4, for example, an
electrochemically reversible redox couple is observed at 1.2 V, effectively identical to those
obtained when NaVO3 was dissolved in 50% H2SO4. Next, the release of PO43- as a function of
H2SO4 concentration was investigated by 31P-NMR spectroscopy, which confirmed the
quantitative presence of free PO43-. Similar indications of V(V) release were supported by UV-
vis spectra for PV2Mo10O405- obtained as a function of H2SO4 concentration and these results were
well supported by substrateoxidation studies as well. Additional studies to reveal the crystal
structure of the active oxidant in the reaction media, is currently in progress are designed to
provide a more detailed understanding of the nature and reactivity of PV2Mo10O405- in strongly
acidic solvents.
References: 1. Neumann, R., Activation of Molecular Oxygen, Polyoxometalates, and Liquid-Phase Catalytic Oxidation
Inorg. Chem., 2010, 49, 3594-3601 2. Sarma B. B., Efremenko I., and Neumann R., Oxygenation of Methylarenes to Benzaldehyde Derivatives
by a Polyoxometalate Mediated Electron Transfer-Oxygen Transfer Reaction in Aqueous Sulfuric Acid, J. Am. Chem. Soc., 2015, 137, 5916–5922
3. Sarma B. B., Carmieli R., Collauto A., Efremenko I., Martin M. L. Jan and Neumann R., Electron Transfer Oxidation of Benzene and Aerobic Oxidation to Phenol, ACS Catal. 2016, 6, 6403-6407 4. Freund M. S. and Lewis N.S., Irreversible Electrocatalyic Reduction of V(V) to V(IV) Using
Phosphomolybdic Acid, Inorg. Chem. 1994, 33, 1638-1643.
P5
Synthesizing Silica Supported Silver Nanoparticles at Different pHs: Tools for
Catalytic Reactions Investigation
Gifty Sara Rolly,a Dan Meyerstein a,b and Tomer Zidkia
a. Department of Chemical Sciences, Ariel University, Ariel, Israel.
b. Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Abstract:
Our work focuses on the synthesis of silica-supported silver nanoparticles in alkaline and
acidic media to investigate the pH effect on different catalytic reactions. Supported metal
nanoparticles are widely employed in catalysis.1 The direct application of metal nanoparticles in
catalysis is quite inconvenient due to their small size and a high tendency to agglomerate. Thus,
metal nanoparticles are deposited on suitable supports such as metal oxides, carbon materials,
polymers, mesoporous silica, etc.2 Since metal-oxides' surface compositions depend on pH, it may
affect the catalytic reactions pathways. We used 40 nm Stober's silica nanoparticles (hydrolysis of
tetraethyl orthosilicate in ethanol-water mixtures in the presence of ammonia) as the support. The
silica nanoparticles were functionalized using bridging molecules to facilitate the attachment of
the silver ions. The reduction was carried out using sodium borohydride (a crucial step in the study)
to form stable alkaline silica supported silver nanoparticles. The obtained supported silver
nanoparticles were acidified using various methods until we got stable nanoparticles. Evident
images of silver deposited on silica at different pHs are picturized in STEM microscopy (Figure
1). The synthesized supported silver nanoparticles can be used to investigate the pH effect on
different catalytic reactions.
Figure 1. STEM micrograph of (a) SiO2-Ag NPs at pH 10 and (b) SiO2-Ag NPs at pH 1.
References:
1. Campelo, J. M., Luna, D., Luque, R., Marinas, J. M. & Romero, A. A. ChemSusChem 2, 18–45 (2009).
2. Zhang, W., Wang, D. & Yan, R. Selective Nanocatalysts and Nanoscience 29–71 (Wiley-VCH Verlag GmbH
& Co. KGaA, 2011).
P6
Highly Active PtxPdy/SnO2/C Catalyst for Dimethyl Ether Oxidation in Fuel
Cells Diwakar Kashyap, Hanan Teller, Alex Schechter
Department of Chemical Sciences, Ariel University, Ariel, 40700, Israel Abstract
Dimethyl ether (DME) is a nontoxic gas that is considered a potential fuel for direct-feed
proton exchange membrane fuel cells (PEMFCs). DME has several advantages over other
fuels, including high energy density, pumpless fuel delivery, liquefied storage, low toxicity
and minimal crossover through Nafion® membranes in PEMFC. However, the low activity of
the state-of-the-art catalyst (Pt50Ru50) for DME oxidation is the main hurdle in the
development of efficient fuel cell devices. In this work, fine layers of SnO2 on high surfacearea
carbon (PtxPdy/SnO2/C) catalysts were synthesized by ethylene glycol-assisted
reduction and characterized by X-ray diffraction, TEM, EDX, XPS, and ICP-OES. The
electrooxidation of DME was systematically studied in a conventional three-electrode cell and a
laboratory prototype direct DME fuel cell (DDMEFC) operating at 70 °C. Compared to other
catalysts reported for DME oxidation, the Pt0.75Pd0.25/SnO2/C shows higher specific power
density in both the conventional three-electrode cell and the fuel cell configurations. The
peak power density delivered by direct gas feed DDMEFCs is 110 mW cm-2 at 0.4 V with only
1.2 mg cm-2 of platinum group metal (PGM) loading.
P7
The role of alcohol sacrificial agents on M/TiO2 photocatalysts towards H2
production reaction: A mechanistic study
Sathiyan Krishnamoorthy,a Ronen Bar-Ziv,b Dan Meyersteina,b and Tomer Zidkia*
a. Department of Chemical Sciences, Ariel University, Ariel, Israel.
b. Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
c. Department of Chemistry, Nuclear Research Centre Negev, Beer-Sheva, Israel.
In the reported study we explored the performance of M/TiO2 (M = Pt, Au) nanoparticles
(NPs) as photocatalysts for HER (Hydrogen Evolution Reaction), with an emphasis on the role of
the alcohol sacrificial reagent under light illumination. TiO2 NPs of fine particle size were
produced by the controlled hydrolysis of Titanium Tetrachloride (TiCl4) as developed by Rabani
et al.[1] and improved by us. The TiO2-NPs were decorated with metal NPs by the addition of the
metal precursors followed by sodium borohydride reduction (NaBH4). Photocatalytic H2
production experiments were conducted in aqueous solutions of methanol, ethanol and 2-propanol
under light illumination with an optimum alcohol concentration of around 2.0 M. The hydrogen
production yields follow the unexpected order: methanol > 2-propanol > ethanol. The addition of
acetone (2-propanol oxidation product) into the reaction system suppressed the H2 formation
suggesting that the alcohol oxidation product reacts with the surface reducing agents (Hydrogen
atoms, hydrides or electrons). These results give a better understanding of the role of the sacrificial
reagents in HER.
Figure 1. The effect of added acetone on H2 yields. (A) Pt/TiO2 NPs, (B) Au/TiO2 NPs.
References
[1] R. Gao, A. Safrany, J. Rabani, Radiat. Phys. & Chem. 2002, 65, 599.
P8
POM encapsulated SiO2 matrices as electron exchange columns and catalysts
for the reductive de-halogenation of HAAs
Neelam1, Dan Meyerstein*1,2, Ariela Burg3, Dror Shamir4, Yael Albo*5
Abstract
Halo-organic acids in aqueous solutions are widespread pollutants. An enormous number of
technologies have been proposed for their elimination1. In this context, reducing electron exchange
columns seem to be an optimal solution for their degradation, as they do not introduce any new
chemical into the solution to be purified2-3. The electron exchange columns used in this study
consist of entrapped polyoxometalates (POMs) in silica sol-gel matrices that were used as the
reducing medium for the reductive de-halogenation of Br3CCO2-, Cl3CCO2
-, BrCH2CO2- and
ClCH2CO2-. The same matrices were also applied as catalysts for the reduction of the investigated
halo-acetates by BH4-. Surprisingly, the results indicate that the mechanisms of de-halogenation of
Br3CCO2-, Cl3CCO2
-, BrCH2CO2- and ClCH2CO2
- differ from each other.
Keywords: de-halogenation/polyoxometalate/halo-acetic acids/sol-gel/water treatment/de-
halogenation mechanisms
(1) C. Chao, W. Xiangyu, C. Ying, L. Huiling, J. Environ. Sci., 20, 945, (2008).
(2) Neelam, Y. Albo, A. Burg, D. Shamir, P. Subramanian, G. Goobes, D. Meyerstein, J. Coord.
Chem., 69, 3449 (2016).
(3) Neelam, Y. Albo, A. Burg, D. Shamir, D. Meyerstein, Chem. Eng. J. 330, 419, (2017).
P9
Łukasz ORZEŁ,a Dorota RUTKOWSKA-ŻBIK,b Mateusz ŚWIRSKI,a Grażyna STOCHELa
a Faculty of Chemistry, Jagiellonian University, Kraków, Poland
b Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Kraków, Poland
Tuning of the chemical stability of the tetrapyrrolic magnesium
complexes on the biosynthetic pathway The biosynthesis of chlorophylls and bacteriochlorophylls shares the initial stages with
heme and other biologically relevant metalloporphyrins. In each case the metal ion is inserted
into the protoporphyrin IX (PPIX) in the enzymatic step, which in the case of photosynthetic
pigments requires a far more specialized Mg-chelatase. Thus formed Mg(PPIX) undergoes
further modifications within the macrocyclic ligand leading to the formation of, respectively,
20- (chlorin) or 18-electron (bacteriochlorin) system. The photosynthetic activity of
chlorophylls and bacteriochlorophylls, resulting from their photochemical and
electrochemical properties, depends also on the resistance to harmful factors, such as light,
redox-active metal ions, reactive oxygen species and other oxidants, which can cause
degradation of the pigments via demetalation, metal substitution or destruction of the
macrocyclic structure of the ligand. In order to gain a better insight into the chemical stability
of magnesium photosynthetic complexes, spectroscopic and electrochemical studies were
carried out in solution. The experiments performed in the presence of Cu(II) ions revealed a
variety of available reaction pathways. Under such conditions, the presence of Mg ion in the
chlorophyll molecule significantly reduces the risk of oxidative opening of the tetrapyrrolic
ring.1 On the other hand, the stability of Mg(II) complexes decreasing with the number of the
pyrrole rings provided an additional justification of the incorporation of the metal ion into
porphyrin prior to the electronic modifications of the tetrapyrrolic system.2 Further
information on how the dimension of the delocalized electron system influence the stability of
metal bonding in the photosynthetic complexes were obtained from the calculations
performed using the Density Functional Theory. 1 Ł. Orzeł et al. Dalton Trans. 2015, 44, 6012-6022
2 Ł. Orzeł et al. J. Coord. Chem. doi.org/10.1080/00958972.2018.1484915
P10
Amino-Guanidine Functionalized Carbon Quantum Dots for selective bacterial
labeling and anti-bacterial applications
Supervisor: Prof. Raz Jelinek Gil Otis
Department of Chemistry, Ben Gurion University of the Negev
Bacterial infection, and especially multi drug resistant bacteria infection, is one of the biggest
global challenges to human health, [1] a fast diagnosis of infection is vital for clinical treatment
as the number of new patients infected by drug resistant bacteria is rising each year.
Thus, extensive efforts have been devoted to developing new methods for bacterial infection
diagnosis and bacterial detection in general, the standard way for characterizing unknown
bacteria is Gram staining, which differentiates bacterial species into two categories (Gram-
positive and Gram-negative). [2]
However, this method has several disadvantages such as laborious procedures and proneness to
generate false positive results, [3]
Regarding bacterial inhibition, the materials widely investigated these days for antibacterial
purpose includes antibiotics (mostly beta lactam antibiotics), noble metal nanoparticles
(especially silver NPs), and quaternary ammonium compounds, all of which have problems such
as antibiotic resistance, high cost and non-environmental friendly synthesis methods.
On the other hand, carbon dots (CDs), are carbon-based fluorescent nanomaterials that have
received much attention recently due to their outstanding photoluminescence properties, low-
toxicity and their simple and low cost synthesis [5], CD’s normally exhibit good biocompatibility
and their chemical properties are easy to adjust, making them good candidates for acting as
antibacterial NPs.
In this work we presented a facile synthesis of amino-guanidine functionalized carbon quantum
dots for selective Gram negative bacterial inhibition and labelling, bacterial strains that were
investigated are E. coli, P. aeruginosa Seattle and P. aeruginosa PAO1, the carbon quantum dots
were also shown to inhibit formation of P. aeruginosa biofilm with high efficiency.
Antibacterial effect of amino guanidine C-dots – Broth dilution method representing the growth of Pseudomonas aeruginosa Seattle with different concentrations of C-dots (A), Bacterial cell viability of different bacteria as a function of C-dots concentration after incubation for 18 hours’(B), Agar dilution method representing the growth of P. aeruginosa Seattle in different C-dots concentrations I - control, II - 0.0625 mg/mL, III – 0.125 mg/mL, IV – 0.25 mg/mL, V – 0.5 mg/mL) growth in 370C for 8 hours (C).
References-
[1]- Levy, S. B.; Marshall, B. Antibacterial Resistance Worldwide: Causes, Challenges and Responses. Nat. Med. 2004, 10, S122
−S129.
[2]- Nugent, R. P.; Krohn, M. A.; Hillier, S. L. Reliability of Diagnosing Bacterial Vaginosis is Improved by a Standardized
Method of Gram Stain Interpretation. J. Clin. Microbiol. 1991, 29, 297−301.
[3]- Oethinger, M.; Warner, D. K.; Schindler, S. A.; Kobayashi, H.; Bauer, T. W. Diagnosing Periprosthetic Infection: False-
Positive Intraoperative Gram Stains. Clin. Orthop. Relat. Res. 2011, 469, 954−960.
[4]- X. Xu, R. Ray, Y. Gu, H. J. Ploehn, L. Gearheart, K. Raker and W. A. Scrivens, J. Am. Chem. Soc., 2004, 126, 12736–
12737.
[5]- Zhu, Anwei, et al. "Carbon‐dot‐based dual‐emission nanohybrid produces a ratiometric fluorescent sensor for in vivo
imaging of cellular copper ions." Angewandte Chemie 124.29 (2012): 7297-7301.
P11
Coupling of Cold plasma and Pyrolysis Synthetic Route for an Active Non-Precious
catalyst for Oxygen Reduction Electrocatalyst in Acidic Electrolytes
Roopathy Mohan, Alex Schechter
Department of Chemical Sciences, Ariel University, Ariel-40700, Israel
Designing novel electrocatalysts for oxygen reduction reaction (ORR) with high activity
and stability and low cost remains a major challenge for the commercialization of low-temperature
fuel cells. In recent years great efforts are dedicated to finding a substitute to state of art Pt- based
electrocatalysts. Low cost metal-nitrogen-carbon materials (MNC) are currently considered as a
promising active ORR catalyst. In our study, we explored a modified approach to the synthesis of
MNC electrocatalysts by applying cold plasma pretreatment step to improve the conventional
high-temperature pyrolysis synthetic method. Plasma treated carbon support was utilized in the
formation of MNC (“M”-Fe, “N”-Nitrogen from Dimethyl formamide, and “C”-plasma treated
carbon support) catalyst. We have found that the ammonia plasma pretreatment step introduces
larger number of iron coordinated Fe-N4 sites as well as nitrogen pyridinic sites in the carbon
matrix during the course of synthesis which are known to facilitate the ORR. Ammonia plasma
treated carbon supported FeNC and untreated control FeNC were characterized by Fourier
transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron
spectroscopy (XPS), Scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy
(EDX) and Brunauer–Emmett-Teller (BET) gas adsorption studies. The electrochemical
characterization was carried out in acid with the relevant electrochemical techniques.
Electrocatalytic activity obtained from Rotating ring disk electrode (RRDE) measurements
suggests that the ammonia treated catalysts NH3-FeNC exhibit enhanced ORR catalytic activity
and good stability towards the ORR with increase in onset and half-wave potentials (Eonset = 0.80
V vs. RHE and E1/2 = 0.64 V vs RHE) and less peroxide yield of 12.0 % at 0.20 V vs RHE compared
to untreated FeNC (Eonset = 0.75 V vs. RHE, E1/2 = 0.58 V vs RHE and H2O2% of 16.0 % at 0.20
V).
Keyword: Fuel cell, Non Pt, MNC catalyst, Pretreatment step, Cold plasma, ORR activity and
acid.
P12
Ag-Pt Bimetallic Nanoparticles Reduction Catalysts: Effects of their Metal
Alloying Composition and H2 Evolution Studies
Shalaka Varshney,1 Ronen Bar-Ziv,2 Dan Meyerstein1, 3 and Tomer Zidki1
1 Department of Chemical Sciences, Ariel University, Ariel Israel 2 Department of Chemistry, Nuclear Research Center Negev, Beer-Sheva, Israel
3Chemistry Department, Ben-Gurion University, Beer-Sheva, Israel
In the advancing field of nanotechnology, metallic nanoparticles (NPs) have gained a tremendous
interest as heterogeneous catalysts and been well established as the subject of a wide research due
to their promising use in catalysis.1-3 Herein, we present a kinetic study of reduction reactions on
Ag, Au, Pt metallic and Ag-Pt bimetallic alloy NPs that were synthesized in aqueous suspensions
without using any stabilizer. Owing to the synergistic and alloying effects between the metals in
Ag-Pt alloy NPs, those have shown superior catalytic performance in the reduction of 4-
nitrophenol to 4-aminophenol by NaBH4. In the bulk, an alloy of Ag and Pt has not been observed
because of the vast immiscibility of these metals, whereas in the nanosized regime, the prepared
Ag-Pt alloy NPs have not only shown higher catalytic efficiency than their mono-metals but also
eliminated the induction time which was observed in the pure Ag NPs case. Kinetics studies of
hydrogen evolution on all NPs were conducted in order to follow the reduction mechanism of the
fastest Ag-Pt catalyst. High-resolution transmission electron microscopy (HR-TEM) and X-Ray
powder diffraction (XRD) studies show that the silver-rich Ag-Pt alloy NPs have a spherical linked
shape and confirm the structure of an alloy with the size of ~4.0 nm. Ag-Pt alloy NPs are also
relatively low-cost catalysts as their one particular metal ratio composition presented the highest
catalytic activity with a relatively low content of Pt.
REFERENCES
1. Herves, P., Perez-Lorenzo, M., Liz-Marzan, L. M., Dzubiella, J., Lu, Y., & Ballauff, M.
(2012). Catalysis by metallic nanoparticles in aqueous solution: model reactions. Chemical
Society Reviews, 41(17), 5577-5587.
2. Singh, A. K., & Xu, Q. (2013). Synergistic catalysis over bimetallic alloy
nanoparticles. ChemCatChem, 5(3), 652-676.
3. Ferrando, R., Jellinek, J., & Johnston, R. L. (2008). Nanoalloys: from theory to applications
of alloy clusters and nanoparticles. Chemical reviews, 108(3), 845-910.
P13
Effect of ancillary ligand proton on the photophysical properties of
some RuIIN6 cores. A proton valve
Shanti G. Patra,a Ennio Zangrandob and Dipankar Dattaa,*
a Dept. of Inorg. Chemistry, Indian Assoc. for the Cultivation of Science, Calcutta 700 032, India
b Department of Chemical and Pharmaceutical Sciences, 34127 Trieste, Italy
Corresponding author e-mail address: [email protected]
Ruthenium complexes of the type RuII(N-N)2L where N-N represents 2,2-bipyridine and 1,10-
phenanthroline and L an ancillary bidentate N-donor ligand having RuIIN6 chromophore are of
much importantance for the plausible applications of their photophysical properties in various
ways.1 In most of the RuII(N-N)2L complexes, 3MLCT is found to be the lowest excited state.
However by changing the physico-chemical properties of L, the nature of the lowest excited can
be modified and thereby the photophysics.2 Herein we present the same with L = benzil mono-
(2-pyridyl)hydrazone,3 LH where H is the dissociable proton. Four complexes [Ru(N-
N)2(LH)](ClO4)2 (1a and 2a) and [Ru(N-N)2L]ClO4 (1b and 2b) have been synthesized. Weak
emissions at 615 nm with quantum yield of 7 x 10-4 -1 x 10-4 are observed in the fluorescence
spectra 1a and 2a when excited at 430 nm in deaerated CH3CN. But 1b and 2b do not fluoresce.
Such differential photophysical behavior is explained in terms of the fact that while a 3MLCT is the
lowest excited state in 1a and 2a (where the LH proton is present), the reactive 3MC is the lowest
excited state in 1b and 2b (where the LH loses the proton). It is pointed out that the proton acts
as a valve in the conduit for the radiative pathways (Figure 1).
Figure 1 A schematic representation of the effect of a proton on the photophysics.
1 V. Balzani, A. Juris, Coord. Chem. Rev., 2001, 211, 97.
2 N. K. Shee, M. G. B. Drew, D. Datta, New J. Chem., 2016, 40, 5002.
3 N. K. Shee, M. G. B. Drew, D. Datta, New J. Chem., 2017, 41, 10415.
P14
Aqueous Reactions of alkyl thiols and sulfinates with iodine and iodate
David M. Stanbury,* Pradeepa Rajakaruna, Yixuan Yang, and John Gorden
Dept. of Chemistry, Auburn University, Auburn, AL 36849 USA
Alkyl thiols (RSH) and sulfinates (RSO2–) are well known to react with iodine and iodate, but no
satisfactory reports exist on the kinetics and mechanisms of these reactions. Here we report on the
reactions of mercaptoethanesulfonate (MESNA) as an example of a typical thiol and methanesulfinate as
a typical sulfinate.
MESNA (HSCH2CH2SO3–), also known as coenzyme M, is a simple thiol having a sulfonate group
that provides high solubility and low vapor pressure without the complications of weak acidity or
oxidizability. MESNA reacts very rapidly with I3– to form the corresponding disulfide, RSSR. When the
two reactants are mixed in equal concentrations on a stopped-flow instrument the absorbance due to I3–
is depleted very rapidly (a few ms) and then there is a partial recovery of the absorbance (a few s).
These two stages are suggested to correspond to the reaction steps:
RSH + I3– -> RSI + H+ + 2I– k = ~ 3 x 106 M–1 s–1
2RSI -> RSSR + I2 k = ~ 5 x 104 M–1 s–1
With excess RSH the absorbance is consumed within the instrument dead time and there is no
absorbance recovery, consistent with the overall reaction stoichiometry. The reaction of MESNA with
excess iodate (IO3–) shows typical clock-reaction character. There is a short initial phase where I3
–/I2 is
not produced because of its very rapid reaction with MESNA. Once all the MESNA is consumed the
absorbance due to I2 rises, corresponding to the net reaction
10RSH + 2IO3– + 2H+ -> 5RSSR + I2 + 6H2O
Methanesulfinate reacts with I3– instantly (stopped-flow dead time) in an equilibrium reaction to
form methanesulfonyl iodide:
RSO2– + I3
– = RSO2I + 2I– KRSO2I
The equilibrium constant was determined spectrophotometrically from the consumption of I3–:
KRSO2I = 1.01 ± 0.04 M at 25 °C.
On the time scale of several-to-hundreds of seconds the absorbance rises and falls. This process first
leads to a pH increase and then a pH decrease. Ultimately the sulfonyl iodide decomposes to yield the
sulfonate, CH3SO3–. The overall reaction is
RSO2– + I3
– + H2O -> RSO3– + 3I– + 2H+
CH3SO2I was precipitated as (CH3SO2I)2.RbI3, and its crystal structure is the first reported for a sulfonyl
iodide.
P15
Polyoxometalate decorated Pt-Nanoparticles
and their Hydrogen Spillover Studies
Aswin Kottapurath Vijaya, Yael Albob, Haim Cohena and Dan Meyersteina,c
a. Department of Chemical Sciences, Ariel University, Ariel, Israel.
b. Department of Chemical Engineering, Ariel University, Ariel, Israel.
c. Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Abstract:
Monolayer polyoxometalate supported platinum nanoparticles, Pt0-NPs, were synthesized and
characterized. Hydrogen spillover from the Pt°-NPs to the polyoxometalate, POM, shell was studied.
Polyoxometalates is an industrially important and chemically interesting class of inorganic compounds
due to their alterable physical and chemical properties. According to the literature both POM and metal
nanoparticles have their own properties.1 Since POMs are molecular anions, they can stabilize colloidal
metal nanoparticles. The redox, catalytic and the photocatalytic properties of POMs can provide distinct
reactivities to such POM stabilized metal nanoparticles.2 Hydrogen spillover effect of platinum and
palladium nanoparticles has been reported earlier.3 Here, our aim is the synthesis of POM (H3PW12O40)
decorated Pt nanoparticles and their hydrogen spillover studies. The obtained POM stabilized Pt
nanoparticles was analyzed and confirmed using a Cryogenic Transmission Electron Microscopy (Cryo-
TEM). The hydrogen spillover effect was confirmed by kinetics studies using the Stopped-Flow method
and characterized using P31 NMR technique.
References:
1. Mitchell, S. G. & de la Fuente, J. M. J. Mater. Chem. 22, 18091 (2012).
2. Wang, Y. & Weinstock, I. A. Chem. Soc. Rev. 41, 7479–7496 (2012).
3. Conner, W. C. & Falconer, J. L. Chem. Rev. 95, 759–788 (1995).
P16
Tailored Pt-Sn based catalyst for Direct Methanol Fuel Cells - A
Computational Research
Itay Pitussi a, Alex Schechter a, Amir Natanb and Haya Korenwitz a
a Department of Department of Chemical Sciences , Ariel University
b Department of Physical Electronics, Tel-Aviv University
ABSTRACT
Pt is the best catalyst for fuel cells, Never the less, the cost of Pt and its poisoning by CO in the ppm level
prevents their commercialization market. Very thin layers of Pt and PtSn alloys supported on metallic Sn
is suggested as catalyst for fuel cells. This approach may provide high utilization of Pt - catalysis and
removal of adsorbed CO from Pt surface via a well-known Pt-Sn bi-functionality mechanism1,2 as well.
The effect of various numbers of layers of Pt or PtSn alloy supported on a well-defined core of Sn was
studied. The adsorption energy of CO and MeOH was studied in comparison to the adsorption energy of
CO and MeOH over pure Pt.
The calculations have been carried out using the Vienna Ab initio Simulation Program (VASP) using
periodic boundaries, PAW PBE pseudopotentials and cutoff energy of 400 eV was used. According to the
computational result, the adsorption energy of CO over a very thin layer of Pt supported on tin is reduced
(less negative, less favored) while methanol is still adsorbed. The same effect, reducing the adsorption
energy of CO while methanol is still adsorbed, was demonstrated on an alloy of PtSn, and an alloy of PtSn
supported on tin as well.
These results indicate that Pt-Sn based catalyst are expected to be an improved catalyst for Direct Methanol
Fuel Cells.
Reference
(1) Wang, K.; Gasteiger, H. a.; Markovic, N. M.; Ross, P. N. On the Reaction Pathway for
Methanol and Carbon Monoxide Electrooxidation on Pt-Sn Alloy versus Pt-Ru Alloy
Surfaces. Electrochim. Acta 1996, 41 (16), 2587–2593.
(2) Mukerjee, S.; Urian, R. C. Bifunctionality in Pt Alloy Nanocluster Electrocatalysts for
Enhanced Methanol Oxidation and CO Tolerance in PEM Fuel Cells: Electrochemical and
in Situ Synchrotron Spectroscopy. Electrochim. Acta 2002, 47 (19), 3219–3231.
P17
The type II Weyl semimetals at low temperatures: chiral anomaly,
elastic deformations, zero sound
Mikhail Zubkov, Meir Lewkowicz
Ariel University, Ariel, Israel
Annals of Physics, in press
Abstract:
We consider the properties of type II Weyl semimetals at low temperatures based on a tight - binding
model. In the presence of an electric field directed along the line connecting the two Weyl points of
opposite chirality the occupied states flow along this axis giving rise to the creation of electron - hole
pairs. The electrons belong to the vicinity of one of the two type II Weyl points while the holes belong
to the vicinity of the other one. This process may be considered as the manifestation of the chiral
anomaly that exists without any external magnetic field. It may be observed experimentally through
the measurement of conductivity.
Next, we consider the modification of the theory in the presence of elastic deformations. In the
domain of the considered model, when it describes type I Weyl semimetals, elastic deformations lead
to the appearance of emergent gravity. In the domain of the type II Weyl semimetals the shape of the
Fermi surface is changed due to the elastic deformations, and its fluctuations represent the special
modes of the zero sound. We find that there exists a one - to - one correspondence between the zero-
sound modes and the elastic waves. Subsequently, we discuss the influence of elastic deformations on
the electrical conductivity. The particularly interesting case is when our model describes the
intermediate state between the type I and the type II Weyl semimetal. In this state, without elastic
deformations, there are Fermi lines instead of Fermi points (type I) /Fermi surface (type II), while the
DC conductivity vanishes. However, even small elastic deformations may lead to the appearance of a
large conductivity.
P18
Stable radicals formation in coals undergoing oxidative weathering
Tze'ela Taub1, Sharon Ruthstein2 and Haim Cohen1, 3
1Dept. of Chemical Sciences, Ariel University, Ariel, Israel, 2Chemistry Dept., Faculty of Exact Science, Bar
Ilan University, Ramat Gan, Israel 3Chemistry Dept., Ben-Gurion University, Be’er Sheva, Israel
Abstract Coals stored under open air, undergoes gas/solid surface reactions defined as Low Temperature
Oxidation (LTO). These weathering processes decrease the calorific value of the coal and different gasses such as carbon oxides (CO, CO2), water, hydrogen (H2) and also some low molecular weight organic gases (C1–5) are released as products.
The mechanism by which the molecular oxygen interacts with the coal macromolecule is suggested to occur in several steps. The main concept is that a chain of radical reactions is taking place, but the exact mechanism is not clear yet. We have succeeded to identify various radical species resulting from these LTO processes which are involved in these reactions.
P19
P20
Sodium Borohydride Reduction Mechanisms Catalyzed by Nobel Metal-
Nanoparticles: silver, gold and platinum
Alina Sermiagin, Dan Meyerstein and Tomer Zidki
Department of Chemical Sciences, Ariel University, Israel
Nowadays, metals are integral part of the chemical industry. In particular, noble metals are
extensively employed in industry, agriculture, jewelry and in the medicinal world. A variety of
industrial catalytic reactions involve extensive usage of metals especially in solid state catalysis.
Often, poisoning of metal surfaces occurs during catalytic reactions under extreme conditions
results in a widespread impact on the environmental pollution.1
One of the most studied resolutions for this environmental problem is catalysis based on
nanoparticles (NPs) and in particular on metal NPs in aqueous solutions. NPs are known for their
high catalytic efficiency in mild conditions and they are extensively investigated due to their
surface to volume ratio properties2. The nature of H-atoms adsorbed on M°-nanoparticles is of
major importance in many catalyzed reduction processes.
Thus, we have chosen to study reduction reactions and in particular water reduction. There are
many studies engaged in catalytic water reduction by sodium borohydride but the mechanism of
these reactions is still obscure.
We are investigating the catalytic reduction by borohydride on metal NPs catalysts (silver, gold
and platinum NPs) using sodium borodeuteride (NaBD4) as an isotopic marker. We are using MS
and TEM to analyze to reactions' products and the catalysts properties. The data obtained
especially by the MS, will give an insight on the reduction mechanisms and the kinetics of the
system investigated.
P21
Electrochemical Ammonia Synthesis using Ruthenium Platinum Alloy at
Ambient Pressure and Low Temperature
Revanasiddappa Manjunatha, Aleksandar Karajic, Alex Schechter*
Department of Chemical Sciences, Ariel University
Ariel Research Park, Ariel, Israel 40700
Abstract
Ammonia was electrochemically produced from nitrogen and water using a ruthenium-
platinum (RuPt) alloy catalyst cathode and a nickel anode under ambient pressure and room
temperature. The rate of ammonia formation was 5.1×10-9 gNH3 s-1cm-2 with a 13.2% faradaic
efficiency at an applied potential of 0.123 V vs. RHE; it reached 1.08×10-8 gNH3 s-1cm-2 at 0.023
V. Ammonia production was investigated under selected potentials and temperatures and analyzed.
Real-time direct electrochemical mass spectrometry (DEMS) analysis of the evolved gases was
measured at various applied potentials. Mainly, the mass-to-charge ratio signals of hydrogen and
ammonia were detected, and their intensities increased with increasing potentials; however, there
was no trace of a hydrazine signal. Compared to metallic ruthenium and platinum catalysts, RuPt
showed a synergistic effect toward electrochemical formation of ammonia due to co-catalysis.
Contact Details of presenting author
Dr. R. Manjunatha,
Prof. Alex Schechter's group,
Department of chemical sciences,
Ariel University,
Ariel
Email: [email protected]
