FROM MOLECULES TO MATERIALS - CURRENT TRENDS AND FUTURE-DIRECTIONS

The development, characterization, and exploitation of novel materials based on the assembly of molecular components is an exceptionally act ive and rapidly expanding field. For this reason, the topic of molecul e-based materials (MBMs) was chosen as the subject of a workshop spons ored by the Chemical Sciences Division of the United States Department of Energy. The purpose of the workshop was to review and discuss the diverse research trajectories in the field from a chemical perspective , and to focus on the critical elements that are likely to be essentia l for rapid progress. The MBMs discussed encompass a diverse set of co mpositions and structures, including clusters, supramolecular assembli es, and assemblies incorporating biomolecule-based components. A full range of potentially interesting materials properties, including elect ronic, magnetic, optical, structural, mechanical, and chemical charact eristics were considered. Key themes of the workshop included synthesi s of novel components, structural control, characterization of structu re and properties, and the development of underlying principles and mo dels. MBMs, defined as ''useful substances prepared from molecules or molecular ions that maintain aspects of the parent molecular framework '' are of special significance because of the capacity for diversity i n composition, structure, and properties, both chemical and physical. Key attributes are the ability in MBMs to access the additional dimens ion of multiple length scales and available structural complexity via organic chemistry synthetic methodologies and the innovative assembly of such diverse components. The interaction among the assembled compon ents can thus lead to unique behavior. A consequence of the complexity is the need for a multiplicity of both existing and new tools for mat erials synthesis, assembly, characterization, and theoretical analysis . For some technologically useful properties, e.g., ferro- or ferrimag netism and superconductivity, the property is not a property of a mole cule or ion; it is a cooperative solid-state (bulk) property-a propert y of the entire solid. Hence, the desired properties are a consequence of the interactions between the molecules or ions, and understanding the solid-state structure as well as methods to predict, control, and modulate the structure are essential to understanding and manipulating such behaviors. As challenging as this is, molecules enable a substan tially greater ability of control than atoms as building blocks for ne w materials and thus are well positioned to contribute significantly t o new materials. The diversity of components and processes leads to th e recognition of the critical role of cross-disciplinary research, inc luding not only that between traditionally different areas within chem istry, but also between chemistry and biochemistry, physics, and a num ber of engineering disciplines. Enhancing communication and active col laboration between these groups was seen as a critical goal for the re search area.