Chemical assembly of an antiferromagnetic macrocyclic molecule containing two inner CoII centers from polymeric cobalt pivalate

Molecular structures of M(II) chelates with compartmental (N,N)-, (N,O)- and (N,S)-donor ligands and articulated metal chelate cycles

Molecular structures of variousd-element M(II) ion chelates with compartmental (N,N)-, (N,O)-, and (N,S)-donor atomic ligands forming as a result of complexing with M(II) three or four articulated metal chelate cycles have been systematized and discussed in detail. It has been shown that, on the whole, such metalmacrocyclic compounds, as a rule, have molecular structures with non-coplanar chelate nodes and non-coplanar macrocycles. The review covers the period 2000–2017.

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.

Charge neutrality of the [V₁₅Sb₆O₄₂(H₂O)]⁶⁻ cluster anion is achieved by simultaneous Sb−N and V−O−Co bond formation. The Sb−N bond has an electron density similar to that of a Sb−O bond. Weak antiferromagnetic exchange interactions are observed between the V^IV and Co^II spin centers.