Design and synthesis of bioactive Ru( <scp>ii</scp> ) complexes: antibacterial activity, biocompatibility and biomolecular binding

Ruthenium(ii) complexes with N- and S-donor ligands have emerged as promising alternatives to conventional antibiotics due to their stability, biocompatibility, and ability to interact with biological macromolecules. In this work, a series of four Ru(ii)-thiazolidine complexes, [Ru(ii)(L1-L4)(<i>p</i>-cymene)Cl]PF₆, were synthesized and structurally characterized using spectroscopic techniques and X-ray crystallography. Their interactions with DNA and proteins showed partial groove binding with calf thymus DNA and a static quenching mechanism with bovine serum albumin (BSA). Biological investigations revealed that two of the complexes exhibited strong antioxidant activity and significant antibacterial effects against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) and <i>Klebsiella pneumonia</i> (KP). Moreover, hemolysis assays confirmed their favourable biocompatibility. These results highlight Ru(ii)-thiazolidine frameworks as promising candidates for antimicrobial drug development. This study not only underscores their therapeutic potential but also advances the role of ruthenium-based coordination chemistry in addressing the persistent challenge of antibiotic resistance.