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Exploring the effect of hydroxylic and non-hydroxylic solvents on the reaction of [VIVO(β-diketonate)2] with 2-Aminobenzoylhydrazide in aerobic and anaerobic conditions. Valence delocalisation in mixed-valence VIV-O-VV species

Abstract

On refluxing [VIVO(β-diketonate)2] namely, [VIVO(acetylacetonate)2] and [VIVO(benzoylacetonate)2] separately with an equivalent or excess amount of 2-aminobenzoylhydrazide (ah) in laboratory grade (LG) CH3OH in aerobic condition afforded non-oxidovanadium(IV) and oxidovanadium(V) complexes of the type [VIV(L1)2] (1), [VVO(L1)(OCH3)]2 (3) and [VIV(L2)2] (2), [VVO(L2)(OCH3)] (4) respectively [where (L1)2- and (L2)2- represent the dianionic forms of 2-aminobenzoylhydrazone of acetylacetone (H2L1) and benzoylacetone (H2L2) respectively (general abbreviation H2L), which formed by the in situ condensation of ah with the respective coordinated β-diketonate] in medium to good yield. The yield of different resulting products depends upon the ratio of ah to [VIVO(β-diketonate)2] e.g., the yield of 1 and 2 complexes increases significantly associated with the decrease in amount of 3 and 4 with the increase of the molar ratio of ah. On replacing CH3OH by a non-hydroxylic solvent, LG CHCl3, the above reaction yielded only oxidovanadium(V) complexes of the type [VVO(L1)(OH)]2 (5), [VVO(L2)(OH)] (6) and [VV2O3(L)2] (7, 8) while, on replacing CHCl3 by another non-hydroxylic solvent, namely LG CH3CN, only the respective [VV2O3(L)2] (7, 8) complex was isolated in 72-78% yield. However, on performing the above reactions in the absence of air using dry CH3OH or dry CHCl3, only the respective [VIV(L)2] complex was obtained suggesting that aerial oxygen is the oxidizing agent and the type of pentavalent product formed depends on the nature of solvent used. Complexes 3 and 4 are converted respectively to 7 and 8 on refluxing in LG CHCl3 via the respective unstable complex 5 and 6. The DFT calculated change in internal energy (∆E) for the reactions: 2[VVO(L2)(OCH3)] + 2H2O → 2[VVO(L2)(OH)] + 2CH3OH and 2[VVO(L2)(OH)] → [VV2O3(L2)2] + H2O is respectively +3.61 and -7.42 kcal/mol suggesting that the [VVO(L2)(OH)] species is unstable and readily transforms to the stable [VV2O3(L2)2] complex. On one-electron reduction at appropriate potential, each of 7 and 8 generated mixed-valence [(L)VVO-(µ-O)-OVIV(L)]- species which showed valence-delocalisation at room temperature and localisation at 77 K. Some of the complexes showed wide range of cytotoxic activity in a dose dependent manner on lung cancer cells comparable to cis-platin.

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Publication details

The article was received on 16 May 2017, accepted on 14 Jul 2017 and first published on 14 Jul 2017


Article type: Paper
DOI: 10.1039/C7DT01776F
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Exploring the effect of hydroxylic and non-hydroxylic solvents on the reaction of [VIVO(β-diketonate)2] with 2-Aminobenzoylhydrazide in aerobic and anaerobic conditions. Valence delocalisation in mixed-valence VIV-O-VV species

    N. Biswas, D. Patra, B. Mondal, S. Bera, S. Acharyya, A. K. Biswas, T. K. Mukhopadhyay, A. Pal, M. G. B. Drew and T. Ghosh, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01776F

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