The CO release properties of κ2N1,N2 Mn(I) tricarbonyl photoCORMs with tridentate benzimidazole coligands

Fac-[MnBr(L1,2-κ2N1,N2)(CO)3] and fac-[MnBr(L3)(CO)3] (1–3) (2,6-bis(benzimidazole-2′-yl)pyridine (L1), 2,6-bis(1-ethyl-benzimidazol-2′-yl)pyridine (L2) and 2-(2-pyridyl)benzimidazole (L3)), capable of CO release upon illumination at 468 nm, were synthesized and fully characterized, including the single crystal X-ray analysis of 1 and 2. The photoCORMs are stable in the dark in DMSO and aqueous buffer under the reducing properties of the myoglobin assay. The κ2N1,N2 bidentate mode of L1,2 ligands changes into meridional, tridentate mode upon illumination as illustrated via solution NMR studies. The influence of the alkylation of benzimidazole ligand on the electronic structure was studied using time dependent density functional theory calculations.