Synergistic cation-to-anion and anion-to-cation interactions in the binding of oxoanions: Syntheses, characterizations, and single-crystal structures of [Co(phen)2CO3]ClO3, [Co(phen)2CO3]BrO3·3.5H2O and [Co(phen)2CO3]IO4

The syntheses, physical, spectroscopic characterizations and crystal structures of [Co(phen)2CO3]ClO3, [Co(phen)2CO3]BrO3·3.5H2O and [Co(phen)2CO3]IO4 are described (phen = 1,10-phenanthroline, C12H8N2). The crystal structures feature “synergistic” directional bonding interactions including cation-to-anion C–H⋯O(anion) bonds and anion-to-cation Cl⋯π and I–O⋯π bonds, as well as cation-to-cation C–H⋯O(carbonato) and π – π stacking interactions. The bromate structure also features distinctive O–H⋯O hydrogen bonding networks involving the water molecules. The facile formation of this series of complex salts with relatively small Ksp values suggests that the [Co(phen)2CO3]+ complex ion may be effective as a binding agent for oxo-anions containing halogen atoms(halates) in an aqueous environment.