Synthesis, structural analysis, DFT study, antioxidant activity of metal complexes of N-substituted thiourea

Abstract

In this work, N-substituted thiourea and its metal complexes were synthesized and characterized by Nuclear magnetic resonance (NMR), Infrared (IR) spectroscopy and X-ray phase analysis. DFT/B3LYP level of theory with 6–31++G(d,p) basis set have been used to determine the geometry, energy and electronic parameters, characterized the stable structures of these compounds. Frontier molecular orbitals energies, energy gap, chemical reactivity descriptors, atomic charges, dipole moment and polarizability have been calculated, the sites of electrophilic and nucleophilic regions where the molecular interactions likely to happen are identified for reagent and complex. The electron density transfer and hyper conjugative interactions are elucidated. The data obtained allowed us to predict the reactivity CuCl2 substituent. It was revealed that the nature of the mentioned substituent favors the formation of a stable five-membered ring via coordinate bonding N6-Cu25 and N17-Cu25. In addition, the thiocarbonyl and methyl groups form a pseudo six-membered ring via the C10H13…S5 hydrogen bond in this complex. It was found that the experimentally and theoretically obtained parameters of the proposed models of thiourea and its complex with CuCl2 have match well. The antioxidant properties of the synthesized compounds were studied in model reactions. Since the study of the mechanism of the antioxidant action of oxidation inhibitors under real conditions of oxidation of lubricating oils is very difficult, the antioxidant effect of the compounds synthesized by us was studied in the oxidation reaction of a model hydrocarbon-cumene, the oxidation mechanism of which was studied in detail. The study of cumene autoxidation in the presence of these compounds showed that they effectively inhibit the autoxidation process.