New thiosemicarbazone Schiff base ligands: Synthesis, characterization, catecholase study and hemolytic activity

Two novel thiosemicarbazones ligands have been synthesized and characterized by FT-IR, ESI-MS, H-1 NMR, and also by single-crystal X-ray diffraction for L1. The crystal structure shows that L1 molecules are planar and are connected via N-H--S and O-H--S interactions. The catecholase activity of is situ copper and cobalt complexes of this ligands has been investigated against 3,5-di-tert-butylcatechol. The progress of the oxidation reactions was closely monitored over time following the strong peak of 3,5-DTBC using UV-Vis. Oxidation rates were determined from the initial slope of absorbance vs. time plots, then analyzed by Michaelis-Menten equations. Catechol oxidation reactions were realized using different concentrations of copper and cobalt acetate and ligands (L/Cu: 1/1, 1/2, 2/1). The results show that all complexes were able to catalyze the oxidation of 3,5-DTBC. Acetate complexes have the highest activity. CuL1 and CoL1 complexes act as a catalyst and inhibitor. While copper and cobalt complexes obtained from ligand L2 illustrate concentration-independent oxidation activation. The hemolysis study performed by L1 increases as a function of its concentration. However, ligand L2 has no hemolytic effect. (C) 2019 Elsevier B.V. All rights reserved.