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

► Synthesis of three Co(III) complexes, [Co(phen)2CO3]ClO3, [Co(phen)2CO3] BrO3·3.5H2O and [Co(phen)2CO3]IO4. ► Synergistic cation-to-anion and anion-to-cation interactions. ► Non-covalent interactions C-H⋯O, O-H⋯O, I-O⋯π, Cl⋯π, π-π are playing crucial role in binding of anions.