Synthesis, characterization and photoinduced CO-release by manganese(i) complexes†
Herein, we report the CO-releasing activity of three new photoCORMs, two with nonbonding pyridine moieties and one with a benzyl group. Compounds [MnBr(CO)3(bpa-κ2)] (2, where bpa = N-benzyl(2-pyridylmethyl)amine); [MnBr(CO)3(pmpea-κ2)] (3, where pmpea = N-(2-pyridylmethyl)-N′-(2-pyridylethyl)amine) and [MnBr(CO)3(bpea-κ2)] (4, where bpea = N-bis(2-pyridylethyl)amine) were synthesized and characterized by common spectroscopic techniques (UV-Vis and IR). Density functional theory studies were also performed to provide new insights into the M–C bond and to assume the orbitals involved in the absorption transitions. Their CO-releasing activities were measured both in organic and in physiological media and compared to that of a previously published compound [Mn(CO)3(dpa-κ3)]Br (1, where dpa = N-bis(2-pyridylmethyl)amine). An increase in the number of members of the chelate from five to six influenced the release of CO, affecting both the binding mode of the ligand and the CO-release process and affecting their potential use as CO-release carriers and therapeutic agents.