Novel OsII-arene Complexes Based on Bipyridyl Derivative Ligands : Synthesis, Crystal Structure, Anticancer Activity and Interaction with DNA/BSA

Five Os-II-arene complexes( 1-5) with bipyridyl derivative ligands were synthesized, where complexes 1-4 were obtained directly from the corresponding precursors, complex 5, however, was received through the anion-exchange experiment from complex 3, with CV being replaced by PF6-. Single crystal structure analyses of complexes 1 and 5 revealed that both complexes adopted typical "piano-stool" conformations, where the "piano stool" consisted of the pi-bond to the arene group, the Os-Cl and two Os-N bonds. The anticancer activities of the complexes towards variable cancer cells were determined by MTT assay. Complexes 1 and 3 exhibited moderate cytotoxicity towards human lung cancer cells ( A549) than complexes 2 and 4. The interactions between the complexes with DNA/BSA were studied by utilization of UV-Vis, fluorescence and CD spectroscopy, and agarose gel electrophoresis. The results indicated that the synthesized complexes except complex 2 could effectively bind to DNA via intercalation. The fluorescence quenching was observed as complexes 1-4 were added into the BSA solution. The quenching constants (K-sv) of complexes 1-4 were larger than 10(4) L/mol, suggesting that the quenching mechanism was static quenching. CD spectra illuminated that the complexes could induce intrinsic conformational changes in DNA. The mobility changes of the form I band were clearly observed in the presence of complexes 1 and 3 by gel electrophoresis assays.