Synthesis and biological activity of binuclear platinum complexes containing two monofunctional cis-[Pt(NH3)2Cl]+ units bridged by 4,4′-dipyridyl selenides or sulfides

The synthesis of four binuclear platinum complexes of general formula {cis-[Pt(NH3)(2)Cl](2)(L)} (NO3)(2) [L is 4,4'-dipyridyl sulfide (compound I), 4,4'-dipyridyl selenide (compound II), bis(3-methyl-4-pyridyl) sulfide (compound III) or bis(3-methyl-4-pyridyl) selenide (compound IV)] has been achieved. These compounds have been characterized by elemental analysis, IR, H-1-NMR, C-13-NMR and Pt-195-NMR spectroscopy. The above dinuclear platinum complexes have been assayed for antitumor activity in vitro against the cisplatin-sensitive L1210 (the mice leukemia) and cisplatin-insensitive HCT8 (the human coloadenocarcinoma) cell lines. The compounds show IC50 values comparable to or higher than cisplatin against L1210 cell line; however, they have lower IC50 values than cisplatin against the cisplatin-insensitive HCT8 cell line. The complexes containing S exhibit a cytotoxicity against the two cancer cell lines superior to the Se analogues. DNA binding studies indicate the compound I possibly interacts with DNA nonintercalatively. The mode of DNA binding of the dinuclear Pt(II) complexes bridged by 4,4'-dipyridyl selenides or sulfides may be different to that of the aliphatic diamine-bridged dinuclear Pt(II) complexes reported previously.