N2O2 tetradentate Schiff base ligands H2Lx (x=1-20) were prepared by reaction of 1,3-propylenediamine, 1,2-ethylendiamine and 1,2-diaminobenzene with appropriate aldehyde and characterized by IR, 1H and 13C NMR. The novel unsymmetrical and symmetrical vanadyl complexes were synthesized by treating an ethanolic solution of the appropriate ligand and one equivalent of VO (acac)2 to yield VOLx (x=1-20). These oxovanadium (IV) complexes were characterized on the basis of their IR, UV–Vis spectroscopy [1]. The complexes were obtained in both monomeric and polynuclear forms. Electrochemical and spectroscopic data (UV-Vis and IR) are related and suggested that they depends not only on the coordination geometry of the oxo-vanadium complex, but also on the kind of the substiuents on phenyl rings and bridge group [2]. These complexes are used as catalyst for the selective epoxidation of olefins [3, 4]. The catalytic activity increases as the number of electron-donor groups increases, and the catalytic selectivity is varied by changing the substituents on the ligands [5]. The multiwall carbon nanotubes (MWCNTs) were used as an immobilization matrix to incorporate vanadium-Schiff base complexs as electron transfer mediator onto a glassy carbon electrode surface [6]. After immobilization of MWCNTs on the electrode surface, the electrode surface was modified with casting V-complexs solution in ACN. The cyclic voltammograms of the modified electrode in aqueous solution is shown a pair of well defined, stable and nearly reversible redox system of V(IV)/V(V) couple with surface confined characteristics. Combination of unique electronic and electrocatalytic properties of MWCNTs and results in a remarkable synergistic augmentation on the response. The modified electrode with VO [(5-Br-sal)2en] showed best catalytic activity toward reduction of H2O2.
