Design and synthesis of new thiobarbituric acid metal complexes as potent protease inhibitors: spectral characterization, thermal analysis and DFT calculations

Abstract

Five novel metal complexes of thiobarbituric acid (TBAH) have been prepared with the general formulae: [Ti(TBA)2(H2O)2]Cl2·2H2O, [Pd(TBA)2]·4H2O, Na[Ag(TBA)2(H2O)2]·4H2O, [Hg(TBA)2(H2O)2] and [Ce(TBA)2(H2O)3]SO4·H2O. The complexes have been fully characterized employing physicochemical and diverse spectroscopic techniques (IR, UV–Vis, mass and 1H NMR) as well as thermal analysis. Elemental analyses and spectroscopic data have showed that the stoichiometries of all complexes were 1:2. Thermal analysis measurements indicated that the complexes have good thermal stability. Density functional theory calculations were carried out at the B3LYP levels of theory with a double basis set, LANL2DZ basis set for titanium, palladium, cerium atoms, or LANL2MB basis set for silver, mercury atoms and 6-31+G(d,p) basis set for the other atoms. The optimized geometry of the ligand and its complexes was obtained based on the optimized structures. The ligand and its metal complexes act as protease inhibitors and repressed their enzymatic activity significantly.