Nonoxido Vanadium(IV) Compounds Involving Dithiocarbazate-Based Tridentate ONS Ligands: Synthesis, Electronic and Molecular Structure, Spectroscopic and Redox Properties

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• 作者：Sanchita Kundu ; Dhrubajyoti Mondal ; Kisholoy Bhattacharya ; Akira Endo ; Daniele Sanna ; Eugenio Garribba ; Muktimoy Chaudhury
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：July 6, 2015
• 年：2015
• 卷：54
• 期：13
• 页码：6203-6215
• 全文大小：724K
• ISSN：1520-510X

文摘

A new series of nonoxido vanadium(IV) compounds [VL₂] (L = L¹鈥揕³) (1鈥?b>3) have been synthesized using dithiocarbazate-based tridentate Schiff-base ligands H₂L¹鈥揌₂L³, containing an appended phenol ring with a tert-butyl substitution at the 2-position. The compounds are characterized by X-ray diffraction analysis (1, 3), IR, UV-vis, EPR spectroscopy, and electrochemical methods. These are nonoxido V^IV complexes that reveal a rare distorted trigonal prismatic arrangement around the 鈥渂are鈥?vanadium centers. Concerning the ligand isomerism, the structure of 1 and 3 can be described as intermediate between mer and sym-fac isomers. DFT methods were used to predict the geometry, g and ⁵¹V A tensors, electronic structure, and electronic absorption spectrum of compounds 1鈥?b>3. Hyperfine coupling constants measured in the EPR spectra can be reproduced satisfactorily at the level of theory PBE0/VTZ, whereas the wavelength and intensity of the absorptions in the UV-vis spectra at the level CAM-B3LYP/gen, where 鈥済en鈥?is a general basis set obtained using 6-31+g(d) for S and 6-31g for all the other elements. The results suggest that the electronic structure of 1鈥?b>3 can be described in terms of a mixing among V-d_xy, V-d_xz, and V-d_yz orbitals in the singly occupied molecular orbital (SOMO), which causes a significant lowering of the absolute value of the ⁵¹V hyperfine coupling constant along the x-axis. The cyclic voltammograms of these compounds in dichloroethane solution display three one-electron processes, two in the cathodic and one in the anodic potential range. Process A (E_1/2 = +1.06 V) is due to the quasi-reversible V(IV/V) oxidation while process B at E_1/2 = 鈭?.085 V is due to the quasi-reversible V(IV/III) reduction, and the third one (process C) at a more negative potential E_1/2 = 鈭?.66 V is due to a ligand centered reduction, all potentials being measured vs Ag/AgCl reference.