Ru^II–Carbonyl photoCORMs with N,N-Benzimidazole Bidentate Ligands: Spectroscopic, Lysozyme Binding Affinity, and Biological Activity Evaluation

The photoinduced carbon monoxide releasing properties of pyridylbenzimidazole-based Ru^II–carbonyl complexes functionalized with alkylated sulfonate (L^SO3H), phthalimide (L^Phth), and morpholine (L^morph) moieties, [RuCl(CO)₃L^SO3H]Cl (1) and [RuCl₂(CO)₂L] {where L = L^Phth (2) and L^morph (3)}, are reported. The geometrical stereochemistry and electronic transitions are assigned with the aid of DFT and TDDFT calculations. The compounds are evaluated for potential antimicrobial and cytotoxic active properties [against noncancerous human embryonic kidney cells (HEK293)]. Complex 2 shows interesting antifungal activity towards Candida albicans and Cryptococcus neoformans, with a similar MIC value of 24 nm. Metalation of hen egg-white lysozyme (HEWL), as a biocompatible carrier, is studied in the dark and upon exposure to light. Stable protein adducts, capable of release CO upon illumination, are formed.