High Cytotoxicity of Ruthenium(II) and Gold(I) Bimetallic Complexes and Its Precursors

A series of Ru(II)-PC_(<i>n</i>)P-Au(I) (<i>n</i> = 1-5) bimetallic complexes were successfully synthesized and characterized with phosphorus (³¹P{H}) and proton (¹H) nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS), supported by crystallographic data. Correlations between resonance shifts and P-Au(I) bond distances provided insight into the electronic environment of the phosphorus centers, while single-crystal X-ray diffraction confirmed the molecular structures. Hirshfeld surface analysis revealed dominant H···H and F···H/H···F interactions, with contact percentages varying systematically with carbon chain length. Biological evaluation showed that the complexes exhibited higher cytotoxicity than cisplatin and melphalan against HeLa and Caco2 cancer cell lines, with pincer ligand carbon chain-length-dependent activity: shorter chains were more potent in HeLa cells, whereas longer chains were more effective in Caco2 cells. Most complexes displayed cytostatic activity, with compound <b>2b</b> demonstrating the best overall performance, combining strong cytostatic properties with high selectivity toward cancerous cells. These findings highlight the structural, electronic, and biological relationships of the complexes, underlining their potential as anticancer agents.