Synthesis, characterisation and evaluation of molecular-orbital parameters, spin-orbit, dipolar and fermi-contact terms of VO2+ ion in thiosemicarbazone complexes

Abstract

Oxovanadium (IV) complexes, [(VO)2L′(acac)] (where L′H3=thiosemicarbazones derived from 2,6-diformyl-p-cresol with thiosemicarbazides) have been synthesised and characterised using physico-chemical techniques. The complexes have a stoichiometry of 2:1 (M/L) wherein phenolic oxygen is coordinated to two metal atoms to form M–O–M bridge. Each metal atom exhibits a coordination number of five. The transition energies ΔE1 and ΔE2 obtained from the electronic absorption spectra of the VO2+-complex in conjunction with the spin-Hamiltonian parameters obtained from EPR data are used to evaluate the spin-orbit coupling constant, the dipolar and the Fermi-contact terms. The bonding coefficients α2 and β2 are evaluated from the available molecular-orbital theories and the experimental data. The various terms evaluated are correlated and the general behaviour of the VO2+ ion in various ligand fields is discussed.