New mono and dinuclear half-sandwiched organoruthenium(II) complexes: Effect of dinuclearity on the biomolecular interaction and cytotoxicity

The present work describes the syntheses and structural characterization of new half sandwiched mono (complex 1) and dinuclear (complex 2) organoruthenium complexes derived from thiosemicarbazone ligand (L1). The molecular structures of compounds were characterized by analytical and multispectroscopic methods which corroborate well with single crystal XRD studies. DFT and TD-DFT studies of compounds revealed that HOMO electron density in L1 is localised on the thiosemicarbazide moiety while the LUMO electron density is evenly distributed over the ligand. However, in complex 1, the HOMO and LUMO is localised on the arene moiety and partially distributed over metal ion while HOMO and LUMO in complex 2 is equally delocalised throughout the complex. The collaborative preliminary DNA binding studies revealed that complexes 1 and 2 exhibited intercalative mode of interaction. The magnitude of DNA binding strength was determined by calculating Kb, K and Ksv values which demonstrated higher DNA binding propensity of complex 2. Furthermore, HSA binding studies of complexes also revealed better binding efficiency of dinuclear complex in contrast to mononuclear complex. The cytotoxic potential of dinuclear complex 2 was examined against triple negative breast cancer cell lines (MDA-MB-468 and MDA-MB-231) via MTT assay.