The CO release properties of κ²: N ¹, N ² Mn(i) tricarbonyl photoCORMs with tridentate benzimidazole coligands

Fac-[MnBr(L^1,2-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 L^1,2 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.