Carbonyl-Terpyridyl-Manganese Complexes: Syntheses, Crystal Structures, and Photo-Activated Carbon Monoxide Release Properties

A set of tricarbonylmanganese(I) complexes derived from three differently substituted terpyridyl (terpy) ligands has been synthesized and characterized by various spectroscopic methods and single‐crystal X‐ray diffraction. The corresponding MnI dicarbonyl complexes, which are among the few examples of such compounds as yet described, were also prepared. The crystal structure of the Mn dicarbonyl species with the stabilizing p‐tolyl‐terpyridyl ligand was successfully obtained. The photochemical properties of all the tricarbonyl complexes have been investigated by using UV/Vis, IR, and NMR spectroscopy as characterization techniques; this detailed study shows the ability of the tricarbonyl MnI complexes to release one molar equivalent of CO in a perfectly controlled manner, a property useful for potential CO‐releasing molecules (CO‐RMs). The decarbonylation reaction is irreversible, and notably differs from what we had previously observed for the corresponding bipyridyl analogues as far as the products and kinetics are concerned. The comparison of the rate of CO decoordination of the different complexes is discussed. Carbonyl‐MnI complexes of terpyridyl derivatives have been synthesized. The tricarbonyl species can lose CO in a perfectly controlled way by a photoirradiation process. Moreover, the X‐ray structure of a rare example of a MnI dicarbonyl complex is reported.