Synergistic cation-to-anion and anion-to-cation interactions in the binding of oxoanions: syntheses, characterizations, and single-crystal structures of [Co(phen)(2)CO3]ClO3, [Co(phen)(2)CO3]BrO3 center dot 3.5H(2)O and [Co(phen)(2)CO3]IO4

The syntheses, physical, spectroscopic characterizations and crystal structures of [Co(phen)(2)CO3]ClO3, [Co(phen)(2)CO3]BrO3 center dot 3.5H(2)O and [Co(phen)(2)CO3]IO4 are described (phen = 1,10-phenanthroline, C12H8N2). The crystal structures feature "synergistic" directional bonding interactions including cation-to-anion C-H center dot center dot center dot O(anion) bonds and anion-to-cation Cl center dot center dot center dot pi and I-O center dot center dot center dot pi bonds, as well as cation-to-cation C-H center dot center dot center dot O(carbonato) and pi - pi stacking interactions. The bromate structure also features distinctive O-H center dot center dot center dot O hydrogen bonding networks involving the water molecules. The facile formation of this series of complex salts with relatively small K-sp values suggests that the [Co(phen)(2)CO3](+) complex ion may be effective as a binding agent for oxo-anions containing halogen atoms(halates) in an aqueous environment. (C) 2011 Elsevier B.V. All rights reserved.