| The preparation and characterization of the thiosemicarbazones (TSC) of three classes of ortho-quinone ligands, viz. 1,2-naphthoquinone, 4-substituted 1,2-naphthaquinone and 9,10-phenanthraquinone are reported. The X-ray crystal structure of the TSCs, viz. 1,2-naphthoquinone thiosemicarbazone (NQTS), 4-Pyrrolidine-1-yl-[1, 2]naphthoquinone 1-thiosemicarbazone (L1TSC), and 9,10-phenanthraquinone (PQTSC) confirms the presence of the E tautomeric arrangement in these compounds. The complexes of synthesized TSCs with the divalent transition metals (Cu, Ni, Pd, and Pt) were prepared. The X-ray crystal structure of the complexes, viz. [Ni(NQTSC)2], [Pd(NQTSC)Cl], [Ni(PQTSC)2], and [Pd(PQTSC)Cl] reveals that the TSC ligands behave as a monoanionic terdentate ligand coordination through carbonyl oxygen, imine nitrogen and thiolato sulfur atoms to the central metal ions. The nickel complexes, viz. [Ni(NQTSC)2] and [Ni(PQTSC)2], are distorted octahedrals and show 1:2 stoichiometry. Copper, palladium, and platinum complexes of the NQTS and PQTSC ligands possess square planar geometry with 1:1 metal to ligand ratio. The copper complexes of L1TSC-L5TSC are square pyramidal dimeric molecules with the sulfur atoms of the TSC ligands acting as a bridge between the copper ions.; All the synthesized compounds were evaluated for their antiproliferation activities against human breast cancer cell lines. The growth of the estrogen-dependent and estrogen-independent cell lines was inhibited in a dose dependent manner and complexes are more effective in inhibiting the growth of multi-drug resistant cells than the sensitive ones. Flow cytometry shows accumulation in the sub-G1 phase of the cell cycle which is a good indication of apoptosis. |
