Synthesis of group 6 (chromium, molybdenum, and tungsten) photoCORMs as potential antimicrobial and anticancer agents

Abstract A new ligand 1 (1,10-phenanthrolin-5-amine, N-(2-fluorenylmethylene)) was synthesized and reacted with group 6 metal carbonyls to form UV activable photoCORMs with the formulation of M(1)(CO)4 (M = Cr, Mo, and W, which correspond to 2, 3, and 4, respectively). All synthesized compounds were characterized by FT-IR, 1H NMR, 13C NMR, CHN elemental analysis, and single crystal X-ray diffraction. Compounds 2–4 contain four COs bonded to the metal centre displaying distorted octahedral geometry, and the CO can be released via UV (365 nm) illumination. Compound 2 displayed the shortest half-life and shortest CO-releasing rate when tested using modified three-layered myoglobin solution assay. All compounds generally showed no appreciable antibacterial activities, with or without the illumination of UV light, except for 2 which demonstrated considerable antifungal activity against Candida albicans and C. tropicalis. In contrast, compounds 1–4 exhibited potent cytotoxicity against human colorectal cancer cell lines (HT-29 and HCT 116) and 2–4 displayed strong photo-induced cytotoxicity against the same cell lines with remarkedly high selectivity.