Monodentate Coordination of N, N′-Disubstituted Thiocarbamide Ligands: Syntheses, Structural Analyses, In Vitro Cytotoxicity and DNA Damage Studies of Cu(I) Complexes

Structural analysis of three novel substituted thiocarbamide ligands N-(naphthyl)-N′-(isobutoxycarbonyl) thiocarbamide (H2L1), N-(4-methoxyphenyl)-N′-(isobutoxycarbonyl) thiocarbamide (H2L2) & N-(2-methoxy-4-nitrophenyl)-N′-(isobutoxycarbonyl) thiocarbamide (H2L3) and their copper(I) complexes [(H2L1)2CuCl] (1), [(H2L2)2CuCl] (2) and [(H2L3)2CuCl] (3) was performed using various spectroscopic techniques (FT−IR, 1H and 13C NMR, UV-Visible),TG analysis and single crystal X-ray studies of (H2L1) and [(H2L1)2CuCl] (1). The copper(I) complexes possess trigonal planar geometry coordinating through two thione sulfur atoms from two ligand molecules and one chloride ion. Two intramolecular hydrogen bonding interactions present between (−N1H) and carbonyl oxygen (−N2H) and coordinated chlorine stabilize the trigonal planar structure of the complexes. Cyclic voltammogram of complexes 1–3 displayed quasireversible redox behaviour corresponding to CuI/CuII couple. Determination of in vitro cytotoxicity of ligands and their complexes using five human carcinoma cell lines 2008, C13* (cervical carcinoma), A2780, A2780/CP and IGROV-1 (ovarian carcinoma) revealed that copper(I) complexes were more potent inhibitors than the ligands against all the cell lines. The most effective were complexes 2 and 3. The comet assay test of complexes 2 and 3 against 2008, C13* and IGROV-1 cell lines indicated significant damage to the DNA structure.