Environment-controlled switching between cyclic hexamer and helical conformations of a water chloride cluster An old compound viewed in a new perspective.pdfVIP

Inorganic Chemistry Communications 8 (2005) 871–873 /locate/inoche Environment-controlled switching between cyclic hexamer and helical conformations of a water chloride cluster: An old compound viewed in a new perspective Manas K. Saha, Ivan Bernal * Department of Chemistry, University of Houston, TX 77204-5003, USA Received 10 May 2005; accepted 20 June 2005 Available online 8 August 2005 Abstract On extrusion of a water molecule from the nano-channels created by the packing of [cis-a-(trien)CoCl2]Cl ? 3H2O, an unprecedented dehydration transition occurs that cause the guest water–chloride hexameric clusters to rearrange into a helical modi?cation. The reverse process is achieved by the introduction of an additional water molecule. ó 2005 Elsevier B.V. All rights reserved. Keywords: Cobalt complex; Water–chloride cluster; Hexamer and helical form The behavior of halogen anions in various aqueous environments has attracted considerable attention [1]. For lack of experimental examples, chloride–water assemblies have, primarily, been studied theoretically [1,2]. The formation of such clustered subunits, and their ultimate supramolecular architecture are principally controlled by hydrogen bonding. In nature, self-assembly is generally dynamic and depends upon the cooperation of various non-covalent interactions. Moreover, con?nement of matter on the nano-meter scale can induce phase transitions not seen in bulk systems [3]. Interestingly, the issues involved are also of direct relevance to atmospheric research. Indeed, it has been discovered recently that airborne aqueous sea-salt aerosols serve as a global source of molecular chlorine, both in the polluted nature environment and in the remote lower marine troposphere [4]. The ClC chloride channels catalyze the selective ?ow of Cl-ions across cell membranes, thereby regulating * Corresponding author. E-mail address: ibernal@ (I. Bernal). electrical excitation in skeletal muscle and the ?ow of salt and water across epit