A structural and biological study on the new 3,5-diacetyl-1,2,4-triazol bis(p-chlorophenyl-thiosemicarbazone) ligand and its bimetallic complexes

Preparation and characterization of the new ligand 3,5-diacetyl-1,2,4-triazol bis(N-4-p-chlorophenylthio-semicarbazone), H5L1, and its bimetallic complexes [Pd(mu-H3L1)](2) and [Pt(mu-H3L1)](2), are described. The molecular structure of the complexes, determined by single crystal X-ray crystallography, reveals that each ligand coordinates, in an asymmetric dideprotonated form, to the metal ions in a square planar geometry. The new compounds synthesized have been evaluated for antiproliferative activity in vitro against NCI-H460, T-47D, A2780 and A2780cisR human cancer cell lines. The cytotoxicity data suggest that these compounds may be endowed with important antitumor properties, especially H5L1, since they exhibit excellent antiproliferative activity surpassing the activity of cisplatin against three of the four tumor cell lines studied. The DNA binding ability of H5L1 and [Pt(mu-H3L1)](2) with calf thymus DNA in Tris-HCl buffer solution (pH = 7.2) was explored by UV-Vis absorption spectroscopy and viscosity measurements. These data indicated that both compounds bind to DNA by a groove binding mode.