Versatile Reactivity and Theoretical Evaluation of Mono- and Dinuclear Oxidovanadium(V) Compounds of Aroylazines: Electrogeneration of Mixed-Valence Divanadium(IV,V) Complexes

Dash, Subhashree P and Roy, Satabdi and Mohanty, Monalisa and Carvalho, M Fernanda NN and Kuznetsov, Maxim L and Pessoa, Joao Costa and Kumar, Amit and Patil, Yogesh P and Crochet, Aurelien and Dinda, Rupam (2016) Versatile Reactivity and Theoretical Evaluation of Mono- and Dinuclear Oxidovanadium(V) Compounds of Aroylazines: Electrogeneration of Mixed-Valence Divanadium(IV,V) Complexes. In: INORGANIC CHEMISTRY, 55 (17). pp. 8407-8421.

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Abstract

The substituted hydrazones H2L1-4 (L1-4 = dibasic tridentate ONO2(-) donor ligands) obtained by the condensation of 2-hydroxy-1-naphthaldehyde and 2-aminobenzoylhydrazine (H(2)hnal-abhz) (H2L1) , 2-hydroxy-1-naphthaldehyde and 2-hydroxybenzoylhydrazine (H(2)hnal-hbhz) (H2L2), 2-hydroxy-1-acetonaphthone and benzoylhydrazine (H(2)han-bhz) (H2L3), or 2-hydroxy-1-acetonaphthone and 2-aminobenzoylhydrazine (H(2)han-abhz) (H2L4) are prepared and characterized. Reaction of ammonium vanadate with the appropriate H2L1-4 results in the formation of oxidoethoxidovanadium(V) (VO)-O-V(OEt)(L1-4)] (1-4) complexes. All compounds are characterized in the solid state and in solution by spectroscopic techniques (IR, UV-vis, H-1, C-13, and V-51 NMR, and electrospray ionization mass spectrometry). Single-crystal X-ray diffraction analysis of 1, 3, and 4 confirms the coordination of the corresponding ligands in the dianionic (ONO2-) enolate tautomeric form. In solution, the structurally characterized (VO)-O-V(OEt)(L)] compounds transform into the monooxido-bridged divanadium(V,V) ((VOL)-O-V)(2)-mu-O] complexes, with the processes being studied by IR and H-1, C-13, and V-51 NMR. The density functional theory (DFT) calculated Gibbs free energy of reaction 2(VO)-O-V(OEt)(L-4)] + H2O reversible arrow ((VOL4)-O-V)(2)-mu-O] + 2EtOH is only 2-3 kcal mol(-1), indicating that the dinuclear complexes may form in a significant amount. The electrochemical behavior of the complexes is investigated by cyclic voltammetry, with the V-V-V-IV E-1/2(red) values being in the range 0.27-0.44 V (vs SCE). Upon controlled potential electrolysis, the corresponding (L)(O)V-IV-O-V-V(O)(L) mixed-valence species are obtained upon partial reduction of the ((VOL)-O-V)(2)-mu-O] complexes formed in solution, and some spectroscopic characteristics of these dinuclear mixed-valence complexes are investigated using DFT calculations and by electron paramagnetic resonance (EPR), with the formation of V-IV-O-V-V species being confirmed by the observation of a 15-line pattern in the EPR spectra at room temperature.

Item Type:	Journal Article
Publication:	INORGANIC CHEMISTRY
Additional Information:	Copy right for this article belongs to the AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	28 Oct 2016 07:18
Last Modified:	28 Oct 2016 07:18
URI:	http://eprints.iisc.ac.in/id/eprint/55150

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