Synthesis and characterization of new neutral Mn(I) tricarbonyl complexes with 8-hydroxyquinoline and imidazole ligands as CO releasing molecules

A series of manganese(I) tricarbonyl complexes formulated as [Mn(8-HQ)(CO)(3)Imd] (HQ = hydroxyquinoline and Imd = imidazole derivatives) was synthesized and fully characterized. These structures could be easily accessed from a common dimeric edifice formulated as [Mn-2(8-HQ)(2)(CO)(6)]. The structure of this complex has been confirmed by X-ray diffraction studies. Its reaction with a range of imidazole derivatives (Imd) yielded the monomeric complexes [Mn(8-hydroxyquinoline)(CO)(3)Imd] with various functional groups as an anchoring point for a vector. Photoactivation of all these complexes by blue-light irradiation led to the liberation of 3 mol of CO per mol of complex as determined experimentally. Spectroscopic and computational methods were employed to explore the mechanism of CO release. Finally, a manganese complex including the more elaborate imidazole ligand N- and C-di-protected histidine was successfully synthesized, opening the way to its direct incorporation in peptides.