Supramolecular Stereochemistry

Proceedings of the NATO Advanced Research Workshop, Hveragerdi, Iceland, September 14--19, 1994

Supramolecular chemistry deals with the organisation of molecules into defined assemblies using non-covalent interactions, including weaker and reversible interactions such as hydrogen bonds, and metal-ligand interactions. The aspect of stereochemistry within such chemical architectures, and in particular chirality, is of special interest as it impacts on considerations of molecular recognition, the development of functional materials, the vexed question of homochirality, nanoscale effects of interactions at interfaces, biocatalysis and enzymatic catalysis, and applications in organic synthesis. Chirality in Supramolecular Assemblies addresses many of these aspects, presenting a broad overview of this important and rapidly developing interdisciplinary field. Topics covered include: Origins of molecular and topological chirality Homochirogenesis Chirality in crystallinity Host-guest behavior Chiral influences in functional materials Chirality in network solids and coordination solids Aspects of chirality at interfaces Chirality in organic assemblies Chirality related to biocatalysis and enzymes in organic synthesis. This book is a valuable reference for researchers in the molecular sciences, materials science and biological science working with chiral supramolecular systems. It provides summaries and special insights by acknowledged international experts in the various fields.

Topics in Stereochemistry, previously edited by "the father of stereochemistry" Ernest L. Eliel, is a longstanding, successful series covering the most important advances in the field. The much-anticipated Volume 25 includes chapters on the following topics: * Stereochemistry of Molecules in Inclusion Crystals * Torsional Motion of Stilbene-type Molecules in Crystals * Supramolecular Networks of Porphyrins * Homo- and Heterochirality in Crystals * Supramolecular Synthesis of 1D Chains and 2D Layers in Hydrogen Bond Networks of Ureas and 2-D Pyrimidinones * Chiral Auxiliaries Powerful for Both Enantioresolution and Determination of Absolutely Stereochemistry by X-Ray Crystallograph * Engineering Stereospecific Reactoins in Crystals: Synthesis of Compounds with Adjacent Stereogenic Quaternary Centers by Photodecarbonylation of Crystalline Ketones * The CH/ Hydrogen Bond: An Important Molecular Force in Controlling the Crystal Conformation of Organic Compounds and Three-Dimensional Structure of Biopolymers * Stereoselective Thermal Solid-State Reactions * Crystal Structures and Functionalities of Platinum (II) Complexes Controlled by Various Intermolecular Interactions

A summary of all the most important aspects of supramolecular science, from molecular recognition in chemical and biological systems to supramolecular devices, materials and catalysis. The 17 chapters cover calixarenes, catenanes, cavitands, cholophanes, dendrimers, membranes and self-assembly systems, molecular modelling, molecular level devices, organic materials, peptides and protein surfaces, recognition of carbohydrates, rotaxanes, supramolecular catalysis. A forward-looking chapter written by J.-M. Lehn indicated the future prospects for the entire field. Audience: Ph.D. students and young researchers in chemistry, physics and biology.

NMR is better suited than any other experimental technique for the characterization of supramolecular systems in solution. The presentations included here can be broadly divided into three classes. The first class illustrates the state of the art in the design of supramolecular systems and includes examples of different classes of supramolecular complexes: catenanes, rotaxanes, hydrogen-bonded rosettes, tubes, capsules, dendrimers, and metal-containing hosts. The second class comprises contributions to NMR methods that can be applied to address the main structural problems that arise in supramolecular chemistry. The third class includes biological supramolecular systems studied by state-of-the-art NMR techniques.

The objectives of the ARW were: - identifying areas and highlighting approaches by which large Supramolecular (SM) Assemblies can be synthesised - reviewing and combining methods to characterise and analyse such assemblies. The first part of the ARW is devoted to reviewing synthetic achievements in recent years for several families of SM compounds, and to bringing out principles for crystal structure design, including novel quantum mechanical methods. Synthesis pertains both to the chemical synthesis of components for SM assembly, and to the subsequent assembly process based on complementarity and non-covalent interactions. The elaboration of multiple recognition "algorithms" concurrently employed (for instance, 1t-1t and hydrogen bonds) has recently reached a high degree of sophistication in the sequence: Molecules -7 Supermolecule -7 SM array -7 Crystal or Conglomerate Novel Large Assemblies comprise synthetic entities with molecular weight as high as 15000, and hybrid SM assemblies between synthetic molecules and DNA. Further developments are foreseen at a higher level of organisation, such as between supermolecules or with electromagnetic fields in photochemical processes. Creation of 2D Assemblies is now a powerful tool for creation and study of SM interactions. Moreover, much is to be learned in going from 2D to 3D assemblies in crystal growth and other forms of organisation such as micelles or liquid crystals. On the other hand, crystal engineering based on Molecular Recognition in the Crystal State leads to novel 2D assemblies occurring within predesigned crystal structures (hydrophobic organic clays or nanoporous networks).

Molecular magnetism is a new field of research dealing with the synthesis and study of the physical properties of molecular assemblies involving open-shell units. It is essentially interdisciplinary, joining together organic, organometallic and inorganic chemists, as well as theoreticians, physicists and materials scientists. At the core of research into molecular magnetism lie design and synthesis of new molecular assemblies exhibiting bulk properties such as long-range magnetic ordering or bistability with an hysteresis effect, which confers a memory effect on the system. In such terms, magnetism may be considered a supramolecular function. The first eight contributions to this volume present the state of the art in organic supramolecular chemistry, emphasising interlocked systems and molecular trees. The following six articles are devoted to molecular materials constructed from organic radicals and transition metal units. Molecular bistability is then focused on, followed by metal-organic and coordination magnetic materials. A new approach to nano-sized particles closes the work.