Design of organometallic molecular and ionic materials

Organometallic crystal engineering is the modeling, synthesis, characteriza tion and evaluation of crystalline materials constituted by organometallic molecules and ions. The properties of solids containing transition metal co mplexes are distinct and diverse from those of purely organic systems as we ll as from those of inorganic materials. In particular, while the periphery of (most) organometallic molecules are 'organic' in nature, since the oute r atoms are usually those of the ligands, the 'cores' are formed by transit ion metal atoms in their (often variable) spin and charge states. These cha racteristics can be exploited to make crystalline materials with predefined physical properties as well as to organize organometallic molecules in com plex supramolecular structures for absorption and desorption of solvent mol ecules, The possibility of utilizing the same building blocks in different ionic conditions (including neutral, e.g. in molecular crystals) permits tu ning of the intermolecular bonding capacity via acid-base reactions. Organo metallic polymorphism is discussed as a possibility for preparing and inter converting crystalline isomers. Pseudo-polymorphism is shown to be advantag eous for the preparation of elusive crystal forms. (C) 2001 Elsevier Scienc e B.V. All rights reserved.