Ruthenium Materials: Synthesis, Characterization, Optical, Antioxidant, and Anticancer Applications

The technological promise of nonlinear optical (NLO) compounds has stimulated intense interest in optoelectronic devices, data storage, photonics, and anticancer therapy. Thiosemicarbazone ruthenium materials are of growing interest because of their tunable ligand framework and coordination sphere, allowing fine control over geometry, electronics, and functional properties. Here, we report an N-substituted salicylaldehyde thiosemicarbazone ligand and a series of octahedral Ru(III) complexes bearing triphenylphosphine or triphenylarsine and halide (Cl, Br) co-ligands. The complexes were characterized by elemental analysis, FT-IR, UV–Vis, EPR, mass spectrometry, and magnetic susceptibility measurements, which together confirm NS-chelation to a low-spin Ru(III) center in a distorted octahedral environment. Their photophysical and NLO responses were assessed by UV–Vis spectroscopy and powder second-harmonic generation measurements (Kurtz–Perry method), revealing promising NLO behavior. In parallel, antioxidant activity and in vitro anticancer effects against HeLa cells were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assays. These results provide insight into ligand-controlled structure–activity relationships, in which the halide (Cl/Br) and ancillary triarylphosphine co-ligands regulate electronic interactions and lipophilicity and ultimately increase biological performance, underscoring the dual materials and medicinal potential of these Ru(III) complexes.