Abstract
2-Aminobenzoylhydrazide (abh) reacts with equimolar amounts of either [VIVO(acac)2] or [VIVO(bzac)2] (where acac− and bzac− are the monoanionic forms of acetylacetone (Hacac) and benzoylacetone (Hbzac), respectively) in the presence of equimolar amounts of 1,10-phenanthroline (phen) to form the octahedral mixed-ligand complexes [VIVO(L1)(phen)] (1) and [VIVO(L2)(phen)] (2), where (L1)2− and (L2)2− are the dianionic forms of the 2-aminobenzoylhydrazone of acetylacetone (H2L1) and benzoylacetone (H2L2). Upon substituting phen by 8-hydroxyquinoline (Hhq), pentavalent [VVO(L1)(hq)] (3) and [VVO(L2)(hq)] (4) complexes were instead obtained. In the crystal structures of 3 and 4, the hydrazone ligands coordinate to the vanadium center through the enolic-O, one imine-N and amide-O in a mer geometry. The amine and the second imine nitrogen form intramolecular hydrogen bonds. Complexes 1 and 2 display quasi-reversible one-electron oxidation peaks near +0.60 V, while the pentavalent 3 and 4 exhibit quasi-reversible one-electron reduction peaks near −0.18 V versus Ag/AgCl in CH2Cl2 solution. EPR spectroscopic studies on 1 and 2 suggest that the unpaired electron is present in the dxy orbital. DFT studies for 3 indicate that the dxy orbital of vanadium is the main contributor to the LUMO.
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Acknowledgments
We thank University Grants Commission (New Delhi, India) for financial assistance. We are thankful to Dr P. Ghosh, Department of Chemistry, R.K. Mission Residential College, Narendrapur, India, for electrochemical measurements and to our College authority for providing research facilities. We are grateful to the learned reviewer 1 for his valuable suggestions. We gratefully acknowledge DST-FIST for instrumental help at R.K. Mission V.C. College, Rahara.
Disclosure statement
No potential conflict of interest was reported by the authors.