Design of organometallic molecular and ionic materials

Organometallic crystal engineering is the modeling, synthesis, characterization and evaluation of crystalline materials constituted by organometallic molecules and ions. The properties of solids containing transition metal complexes are distinct and diverse from those of purely organic systems as well as from those of inorganic materials. In particular, while the periphery of (most) organometallic molecules are 'organic' in nature, since the outer atoms are usually those of the ligands, the 'cores' are formed by transition metal atoms in their (often variable) spin and charge states. These characteristics can be exploited to make crystalline materials with predefined physical properties as well as to organize organometallic molecules in complex supramolecular structures for absorption and desorption of solvent molecules, The possibility of utilizing the same building blocks in different ionic conditions (including neutral, e.g. in molecular crystals) permits tuning of the intermolecular bonding capacity via acid-base reactions. Organometallic polymorphism is discussed as a possibility for preparing and interconverting crystalline isomers. Pseudo-polymorphism is shown to be advantageous for the preparation of elusive crystal forms. (C) 2001 Elsevier Science B.V. All rights reserved.