SYNTHESIS, CHARACTERIZATION AND CATALYTIC STUDIES OF SOME OXOVANADIUM(IV) COMPLEXES OF TETRADENTATE SCHIFF BASE LIGANDS

Oxovanadium(IV) complexes of the type [VO(L-1)]center dot H2O and [VO(L-2)]center dot H2O [where L-1 = N,N'-(+/-)-trans-bis(2,4-dihydroxybenzophenone)-1,2-cyclohexanediamine and L-2 = N,N'-(+/-)-trans-bis(2,4-dihydroxy-5-nitrobenzophenone)-1,2-cyclohexanediamine respectively] have synthesized and characterized by elemental analyses, magnetic susceptibility measurements, electronic, IR, ESR spectra and X-ray diffraction studies. The thermal behavior of ligands and their complexes have been studied using TG-DTG technique. The IR spectral data reveal that the ligands behave as dibasic tetradentate nature coordinating through azomethine nitrogen and phenolic oxygen atoms. The magnetic susceptibility measurements, electronic and ESR spectral data of complexes indicate a mononuclear square pyramidal geometry around VO(IV) ion. The solid state electrical conductivity of these complexes was measured by two probe method and compounds showed semiconducting behavior as their conductivity increases with increase in temperature. Both the complexes [VO(L-1)center dot H2O and [VO(L-2)]center dot H2O were also tested for their catalytic epoxidation of styrene utilizing hydrogen peroxide as an oxidant.