Synthesis of mixed-ligand complexes of VO2+ and VO3+ incorporating hydrazone, 1,10-phenanthroline and 8-hydroxyquinoline |
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Authors: | Nirmalendu Biswas Debashis Patra Bipul Mondal Michael GB Drew |
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Institution: | 1. Department of Chemistry, Ramakrishna Mission Vivekananda Centenary College, Kolkata, India;2. Department of Chemistry, The University of Reading, Reading, UK |
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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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Keywords: | V(IV) and V(V) complexes hydrazone complexes X-ray structure electrochemistry EPR spectra DFT study |
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