Photoactivatable properties of water-soluble fac-Mn(CO)3 bearing N∧O bidentate pyridine ligands

Abstract

Two water-soluble fac-Mn(CO)3 based complexes of the general formula fac-[MnBr(CO)3(N∧O)] (N∧O = pyridine-2-carboxaldehyde (A), and 2-acetylpyridine (B)) were described for their potential CO releasing properties upon illumination at 468 nm, solvatochromism features and cytotoxicity against different malignant cell lines in both the dark and upon the exposure to light source. Negative solvatochromism may be responsible for the red shift of the metal-to-ligand charge transfer band in increasingly less polar solvents. Compound B, which had been functionalized with 2-acetylpyridine, released CO in water faster than complex A, suggesting the role of the methyl group in regulating the CO release kinetics. According to myoglobin assay, the CO release pathway in water is slower than in DMSO revealing to the role of the solvent in controlling the CO release kinetics of Mn(I) carbon monoxide releasing molecules.