Oxidovanadium Catechol Complexes: Radical versus Non-Radical States and Redox Series
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- 作者：Suman Kundu ; Suvendu Maity ; Thomas Weyherm眉ller ; Prasanta Ghosh
- 刊名：Inorganic Chemistry
- 出版年：2013
- 出版时间：July 1, 2013
- 年：2013
- 卷：52
- 期：13
- 页码：7417-7430
- 全文大小：547K
- 年卷期：v.52,no.13(July 1, 2013)
- ISSN：1520-510X
文摘
A new family of oxidovanadium complexes, [(L1R)(VO)(LR鈥?/sup>)] (R = H, R鈥?= H, 1; R = H, R鈥?= -CMe3, 2; R = H, R鈥?= Me, 3; R = -CMe3, R鈥?= H, 4 and R = -CMe3, R鈥?= -CMe3, 5), incorporating tridentate L1RH ligands (L1RH = 2,4-di-R-6-{(2-(pyridin-2-yl)hydrazono)methyl}phenol) and substituted catechols (LR鈥?/sup>H2) was substantiated. The V鈥揙phenolato (cis to V鈺怬), V鈥揙CAT (cis to V鈺怬) and V鈥揙CAT (trans to V鈺怬) lengths span the ranges, 1.894(2)鈥?.910(2), 1.868(2)鈥?.887(2), and 2.120(2)鈥?.180(2) 脜. The metrical oxidation states (MOS) of the catechols in 1鈥?b>5 are fractional and vary from 鈭?.43 to 鈭?.60. The 51V isotropic chemical shifts of solids and solutions of 1鈥?b>5 are deshielded (51V CP MAS: 鈭?9.8 to +248.6; DMSO-d6: +173.9 to +414.55 ppm). The closed shell singlet (CSS) solutions of 1鈥?b>5 are unstable due to open shell singlet (OSS) perturbations. The ground electronic states of 1鈥?b>5 are defined by the resonance contribution of the catecholates (LR鈥?/sup>CAT2鈥?/sup>) and LR鈥?/sup>SQ鈥撯€?/sup> coordinated to the [VO]3+ and [VO]2+ ions. 1鈥?b>5 are reversibly reducible by one electron at 鈭?0.58鈥?.87) V, referenced vs ferrocenium/ferrocene, to VO2+ complexes, [(L1R鈥?/sup>)(VO2+)(LR鈥?/sup>CAT2鈥?/sup>)]鈭?/sup> [1鈥?b>5]鈭?/sup>. 1鈥?b>5 display another quasi-reversible or irreversible reduction wave at 鈭?0.80鈥?.32) V due to the formation of hydrazone anion radical (L1R2鈥撯€?/sup>) complexes, [(L1R2鈥撯€?/sup>)(VO2+)(LR鈥?/sup>CAT2鈥?/sup>)]2鈥?/sup>, [1鈥?b>5]2鈥?/sup>, with S = 1 authenticated by the unrestricted density functional theory (DFT) calculations on 12鈥?/sup> and 32鈥?/sup> ions. Frozen glasses electron paramagnetic resonance (EPR) spectra of [1鈥?b>5]鈭?/sup> ions [e.g., for 2, g|| = 1.948, g = 1.979, A|| = 164, A = 60] affirmed that [1鈥?b>5]鈭?/sup> ions are the [VO]2+ complexes of LR鈥?/sup>CAT2鈥?/sup>. Spectro-electrochemical measurements and time-dependent DFT (TD DFT) calculations on 1, 3, 1鈥?/sup>, 3鈥?/sup>, and 12鈥?/sup> disclosed that the near infrared (NIR) absorption bands of 1鈥?b>5 at 800 nm are due to the CSS-OSS metal to ligand charge transfer which are red-shifted in the solid state and disappear in [1鈥?b>5]鈭?/sup> and [1鈥?b>5]2鈥?/sup> ions.
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