Supramolecular chemistry, Israel

The 12th Int’l Symposium on Supramolecular Chemistry (ISSC-XII) was held in October, 2002 in the resort city of Eilat, Israel. The unique sights of the Red Sea, the surrounding desert and the red-colored ore-rich mountains, enhanced a romantic welcome reception by the swimming pool of the Magic Palace Hotel (the Symposium venue). ISSC-XII was attended by senior and junior scientists from Asia (Japan, South Korea, India, China & Hong Kong), Europe (Moldova, Russia, Poland, Czech Republic, Germany, The Netherlands, Switzerland, France, Italy, UK), Africa (Ghana) and North America (Canada, US), as well as from Israel. A number of travel grants sponsored by the Vigevani Foundation and the IUCr, were awarded to young participants. The Symposium focused on recent advances in both basic as well as applied research of supramolecular chemistry and materials, encompassing a wide spectrum of subjects from nano-science, through structural and functional chemistry, to biomaterials.

The session on the self-assembly and function of nano-structures. Its highlights included lectures by J. Sagiv (Israel) on a hierarchical fabrication of organic-inorganic nano-composite architectures in thin films, as a potentially useful technology for the construction of functional nano-devices, and by S. Stupp (USA) on the self-assembly of organic nano-fibers with interesting mechanical properties which could be used in bone repair in medicine. M. Rampi (Italy) showed self-assembled monolayers with transistor-type functionality in the context of molecular electronics, while E. Joselevich (Israel) focused on carbon nanotubes as building blocks. Very colorful presentations on supramolecular materials with unique optical properties were delivered by M. Hollingsworth (USA) on ferroelastic and ferroelectric domain switching in solid inclusion complexes of urea and calixarenes, and by P. de Silva (Northern Ireland) on the application of luminescent compounds as information processors and their utility in medical treatment. De Silva and S. Speiser (Israel) showed how binary logic operations could be implemented at the molecular scale.

Advances in the syntheses and characterization of new supramolecularly ordered compounds, which can be used in electronic devices, were highlighted by P. Bäuerle (Germany) and M. Drain (USA) who referred to conjugated macrocyclic oligothiophene oligomers and porphyrin-array-based functional photonic materials, respectively. I. Willner (Israel) explored nanoparticle architectures, composed of organic moieties and either gold or cadmium sulfide nanoparticles, which have photonic, electronic and sensoric functionalities. J. Fuhrhop (Germany) described controlled synthesis of porphyrin-based nano-assemblies on gold and silicate substrates/particles. D. Schlüter (Germany) described the elegant synthesis of fourth and fifth generation dendronized polymers and their behavior on solid interfaces. These polymers, when positively charged on their surface, can be wrapped by DNA strands to yield poly-electrolyte aggregates. T. Aida (Japan) reported the beautiful design of light-harvesting dendritic macromolecules and their application to materials science. His systems consist of gigantic porphyrin dendrimers that can effectively capture visible photons. Design of smaller multiporphyrin assemblies for artificial photosynthesis was presented by Y. Kobuke (Japan). J. Miller (USA) added an enlightening review of supramolecular organometallic materials exhibiting the technological important property of bulk magnetism.

S. Zimmerman (USA) led the discussion on molecular recognition, illustrating the construction of supramolecular polymers from 'sticky' monomeric entities that associate strongly in a predictable manner. Molecular tectonics, which relates to the design by self-assembly of molecular networks with pre-programmed structures, was further dealt with by W. Hosseini (France). He showed that the formation of molecular networks may be achieved through an iterative self-assembling process by using programmed building blocks which contain both recognition and iteration information. Related presentations by N. Kobayashi (Japan), I. Williams (Hong Kong) and D. Soldatov (Canada), focused on the designed construction of new hybrid organic-inorganic supramolecular complexes and coordination polymers. Structure, properties and functionality studies of inclusion host-guest chemistry based on a wide variety of organic and inorganic host systems were then addressed by K. Komatsu (Japan) - fullerene-based nanomaterials, R. Ungaro (Italy) - multivalent calixarene ligands as specific molecular delivery systems potentially useful in environmental chemistry, P. Lhoták (Czech Republic), K. Suwinska (Poland), Y. Inoue (Osaka, Japan), W. Saenger (Germany), J. Lipkowski (Poland), H. Gies (Germany) - zeolites, and T. Iwamoto (Japan).

J. Sessler (USA) discussed a large variety of polypyrrole-based anion binding agents. Stereoid-based receptors for inorganic anions as well as for carboxylates were presented by A. Davis (UK) and B. Smith (USA). These and related receptors were found effective in transport experiments through the interior of non-polar membranes. Anion-controlled assembling of porphyrin-guanidine-, porphyrin-alkaloid- and porphyrin-guanosine-conjugates were described by V. Kral (Czech Republic). U. Maitra (India) spoke on self-assembled fibrillar networks formed from bile acid analogs.

J. Sanders (UK), envisaged new opportunities for molecular recognition and catalysis by applying the methodology of dynamic combinatorial chemistry. Z. Gross (Israel) highlighted the unique catalytic properties of the corrole macrocycles. L. Mandolini (Italy) described new organometallic ditopic catalysts based on various functionalized platforms (calixarenes, pyridines and azacrownethers) with high substrate selectivity features. Dendrimer-based reaction catalysts were also discussed by M. Portnoy (Israel). In the biological area, F. Diederich (Switzerland) evaluated on molecular recognition features at enzyme active sites, highlighting the successful design of de novo nonpeptidic enzyme inhibitors. These studies were based on detailed crystallographic characterization of the enzyme structures.

The Symposium was concluded by sessions devoted to biological systems. R. Nolte (The Netherlands) described methodologies to construct supramolecular assemblages from building blocks which contain the desired information encoded within them for a stepwise, hierarchical assembly process. G. von Kiedrowski (Germany) discussed design principles used to generate noncovalent 3D-nanoobjects in which both the topology and the geometry is well defined by complementary molecular recognition algorithms. Turning oligopeptides into molecular machines (receptors and catalysts) was also the theme of P. Scrimin’s (Italy) lecture. G. Gokel (USA) described a synthetic heptapeptide system as an effective transporting agent of chloride ions through membranes. New artificial receptors based on aminopyrazole nuclei for protein recognition were designed by T. Schrader (Germany). A. Coleman (France) described the construction of organized and active assemblies based on protein (Bovine Serum Albumin or Fibrin)/salt mixtures prepared in the form of thin film gels, which exhibit electrical conductivity, frequency dependent switching capacity and differential conductivity paths along and across the dendritic architectures.

Poster contributions were displayed throughout the Symposium, their themes paralleling the range of topics encompassed by the oral program.

Israel Goldberg