ic5b00359_si_002.cif (1.34 MB)
Download fileNonoxido Vanadium(IV) Compounds Involving Dithiocarbazate-Based Tridentate ONS Ligands: Synthesis, Electronic and Molecular Structure, Spectroscopic and Redox Properties
dataset
posted on 06.07.2015, 00:00 authored by Sanchita Kundu, Dhrubajyoti Mondal, Kisholoy Bhattacharya, Akira Endo, Daniele Sanna, Eugenio Garribba, Muktimoy ChaudhuryA new series of nonoxido vanadium(IV)
compounds [VL2] (L = L1–L3) (1–3) have been synthesized using
dithiocarbazate-based tridentate
Schiff-base ligands H2L1–H2L3, 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 VIV complexes that reveal a rare distorted
trigonal prismatic arrangement around the “bare” 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 1–3. 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 “gen” 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 1–3 can
be described in terms of a mixing among V-dxy, V-dxz, and V-dyz 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 (E1/2 = +1.06 V) is due to the
quasi-reversible V(IV/V) oxidation while process B at E1/2 = −0.085 V is due to the quasi-reversible V(IV/III)
reduction, and the third one (process C) at a more negative potential E1/2 = −1.66 V is due to a ligand centered
reduction, all potentials being measured vs Ag/AgCl reference.