Chemistry of molecular and supramolecular structures of vanadium(IV) and dioxygen-bridged V(V) complexes incorporating tridentate hydrazone ligands

Four hydrazone ligands: 2-benzoylpyridine benzoyl hydrazone (HBPB), di-2-pyridyl ketone nicotinoyl hydrazone (HDKN), quinoline-2-carbaldehyde benzoyl hydrazone (HQCB), and quinoline-2-carbaldehyde nicotinoyl hydrazone (HQCN) and four of their complexes with vanadyl salts have been synthesized and characterized. Single crystals of HBPB and complexes [VO(BPB)(μ2-O)]2 (1) and [VO(DKN)(μ2-O)]2·½H2O (2) were isolated and characterized by X-ray crystallography. Each of the complexes exhibits a binuclear structure where two vanadium(V) atoms are bridged by two oxygen atoms to form distorted octahedral structures within cis-N2O4 donor sets. In most complexes, the uninegative anions function as tridentate ligands, coordinating through the pyridyl- and azomethine-nitrogen atoms and enolic oxygen whereas in complex [VO(HQCN)(SO4)]SO4·4H2O (4) the ligand is coordinated in the keto form. Complexes [VO(QCB)(OMe)]·1.5H2O (3) and 4 are found to be EPR active and showed well-resolved axial anisotropy with two sets of eight line pattern.

Four hydrazone ligands HBPB, HDKN, HQCB, HQCN and four vanadium complexes with general formulae [VO(BPB)(μ2-O)]2] (1), [VO(DKN)(μ2-O)]2·2H2O (2), [VO(QCB)(OMe)]·1.5H2O (3) and [VO(HQCN)(SO4)]SO4·4H2O (4) were synthesized and characterized by a variety of physico-chemical techniques. Single crystals of HBPB and complexes 1 and 2 were isolated and characterized by X-ray crystallography. The complexes 3 and 4 are EPR active and showed axial anisotropy with two sets of eight line patterns in DMF at 77 K.Figure optionsDownload as PowerPoint slide