Supramolecular association of water molecules forming discrete clusters in the voids of coordination polymers

The fundamental importance of water in many biological, chemical and physical processes has prompted enormous curiosity for this liquid from theoreticians and experimentalists alike. However, water is not a simple liquid and many of its properties are considered anomalous. Hydrogen bonding interactions, their fluctuations and rearrangement dynamics determine the properties of liquid water. A major obstacle to understand this liquid is a correct description of the cooperative nature of H-bonding among a collection of water molecules. The key here is precise structural data of various hydrogen-bonded networks of water clusters in different restricted environments. How discrete water clusters assume structures that are different from the gas phase structures based on theoretical studies can throw light on the effect of environments on the H-bonded networks of this liquid. Besides, the degree of structuring of a water cluster that can be imposed by its environments and vice versa, can be of importance in the self-assembly of metal-organic frameworks. This review deals with the study of discrete water clusters present in metal-organic framework structures. (C) 2009 Elsevier Ltd. All rights reserved.