Role of the axial ligand in determining the cytotoxicity and CO releasing properties of light-mediated tricarbonyl Mn(I) complexes containing benzimidazole ligand

In this contribution, we synthesized and characterized three Mn(I) carbon monoxide releasing molecules with a general formula of [MnX(CO) 3 L] (X = Br − , Cl − and NCS − ; L = 1 H -benzimidazol-2-ylmethyl-( N- phenyl)amine)) using a variety of analytical and spectroscopic tools. Next, we examined how various axial ligands affected the dark stability and photoactivatable carbon monoxide-releasing properties under 468 nm light exposure, both with and without hen white egg lysozyme (HEWL), histidine as well as calf-thymus DNA. Depending on the nature of the biomolecule, one or two isosbestic points emerged during the illumination, indicating the biomolecule's function in regulating the CO-depleted species' characteristics. When the myoglobin solutions of the chloride and isothiocyanate complexes were illuminated at 395 nm for 22 minutes, about 1.22−1.45 CO equivalents were released. The three complexes demonstrated significant cytotoxicity against leukaemia cells in both dark and light environments, with IC 50 values ranging from 9.75 to 19.8 μM. Only the chloride-containing CORM, was toxic against the normal Vero cells. Light exposure at 468 nm boosted the complexes’ oxidizing power by generating more ROS than in the dark especially in the case of the bromide complex.