Covalent Co-O-V and Sb-N Bonds Enable Polyoxovanadate Charge Control

The formation of [{Co^II(teta)₂}{Co^II₂(tren)(teta)₂}V^IV₁₅Sb^III₆O₄₂(H₂O)]·ca.9H₂O [teta = triethylenetetraamine; tren = tris(2-aminoethyl)amine] illustrates a strategy toward reducing the molecular charge of polyoxovanadates, a key challenge in their use as components in single-molecule electronics. Here, a V-O-Co bond to a binuclear Co²⁺-centered complex and a Sb-N bond to the terminal N atom of a teta ligand of a mononuclear Co²⁺ complex allow for full charge compensation of the archetypal molecular magnet [V₁₅Sb₆O₄₂(H₂O)]^6-. Density functional theory based electron localization function analysis demonstrates that the Sb-N bond has an electron density similar to that of a Sb-O bond. Magnetic exchange coupling between the V^IV and Co^II spin centers mediated via the Sb-N bridge is comparably weakly antiferromagnetic.