Synthesis, structure, and electrochemistry of trans-[Co^III{(BA) ₂pn}(L)₂]ClO₄ complexes

The structure, spectroscopic, and electrochemical properties of [Co{(BA)₂pn}(L)₂]ClO₄ complexes, where (BA)₂pn = N,N'-bis(benzoylacetone)-1,3-propylenediimine dianion and the two ancillary ligands (L) are pyridine, py (1), and 4-methylpyridine, 4-Mepy (2), have been investigated. These complexes have been characterized by elemental analyses, IR, UV-Vis and ¹H-NMR spectroscopy. The crystal structure of [Co{(BA)₂pn}(py)₂]ClO₄ (1) has been determined by X-ray diffraction. The coordination geometry around cobalt(III) is best described as a distorted octahedron. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co ^III-Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial N(py)-cobalt bonds. This process becomes quasi-reversible upon the addition of excess py ligands. The second reduction step of Co^II/I shows reversible behavior and is not influenced by the nature of the axial ligands.