Synthesis, characterization, thermal stability, electrochemical behavior, and antioxidant activity of new oxovanadium(iv) and iron(ii) tetradentate Schiff base complexes

Abstract

Two new tetradentate oxovanadium(IV) and iron(II) Schiff base complexes have been prepared by the interaction of vanadyl(IV) and iron(III) acetylacetonate with the ligand obtained from the reaction of ethylenediamine and 5′-(N-methyl-N-phenylaminomethyl)-2′-hydroxyacetophenone in methanol. These complexes have been characterized by means of different spectroscopic techniques such as UV–visible, FT-IR, mass spectrometry, and elemental analysis. In addition, thermogravimetric (TG) and differential thermogavemetric analysis (DTG) have been utilized to investigate the thermal stability of these complexes. Results showed that both Schiff base complexes decompose in five consecutive stages, and a mechanism has been proposed for each stage of thermal decomposition. Thermogravimetric analysis has been carried out using four different heating rates of 5, 10, 15, and 20 °C min, and the kinetic parameters of these complexes have been calculated using the Kissinger method. Cyclic voltammetry has been employed to examine the electrochemical behavior of the two synthesized complexes in dimethyl sulfoxide (DMSO) at a glassy carbon electrode. Each of these complexes displayed one quasi-reversible single electron transfer peak near 0.255 V vs. saturated calomel electrode (SCE) for the V(V)–V(IV) couple and near −0.690 V vs. SCE for the Fe(III)–Fe(II) redox couples, respectively. Finally, the antioxidant activity of the newly prepared complexes has been investigated using the 2,2-diphenyl-1-picrylhydrazyle (DPPH) free radical scavenging assay. Results revealed that the oxovanadium Schiff base complex exhibits good antioxidant activity.