Synthesis, structure, and cytotoxicity of complexes of zinc(II), palladium(II), and copper(I) chlorides with (−)-camphor thiosemicarbazone

Complexes [Zn(L2)2Cl2], [Pd2(L2)2Cl4], and CuL2Cl, where L2 is (−)-camphor thiosemicarbazone, were synthesized. The structures of complexes [Zn(L2)2Cl2] and [Pd2(L2)2Cl4] were determined by X-ray diffraction. The crystal structure of complex [Zn(L2)2Cl2] contains mononuclear molecules with distorted tetrahedral {ZnCl2S2} coordination units and monodentate L2 ligands. Complex [Pd2(L2)2Cl4] has binuclear structure with Pd metal centers linked by L2 ligands via μ2-S atoms. Complex CuL2Cl, according to IR and NMR spectra contains S and Cl atoms in the coordination sphere of ion Cu+. Complexes [Pd(tsc)Cl2] and Zn(tsc)2Cl2 (where tsc is thiosemicarbazide) were also obtained to determine the influence of the terpene moiety on cytotoxic properties of these compounds. Mononuclear complex [Pd(tsc)Cl2] contains an NSCl2 planar square coordination polyhedron, and tsc is a bidentate chelate ligand. The effects of tsc, L2, and the complexes with tsc and L2 on viability of the MCF-7 cell line were investigated next. The results showed that tsc and L2 are nontoxic at the tested concentrations (1–50 μM). All the complexes exerted a significant dose-dependent cytotoxic effect, whereas complex CuL2Cl was found to have the lowest half-maximal inhibitory concentration (IC50).