Carbon monoxide (CO) is a poisonous gas. But like NO, it has important physiological roles to play. Metallocarbonyl complexes decompose under appropriate conditions to release CO and therefore, represent a promising class of future pharmaceuticals as CO-releasing molecules (CORMs). Among the reported methods for triggering CO-release, photo-activation is particularly favoured due to its easy controllability of timing and location. For most photoCORMs, high energy, short wavelength light is usually needed to trigger the dissociation of CO. Such wavelengths do not penetrate deeply into tissue and are potentially harmful, so systems responsive to longer wavelength visible / near-infrared (NIR) light are needed to activate the CO release. One of the strategy is to use heterogenic dinuclear metal complexes. These complexes can exhibit additional metal-metal-bond to ligand charge transfer band (MMLCT) in additional to the MLCT band (metal to ligand charge transfer), which can absorb longer wavelength photons to result in long wavelength absorbance. In this work, some manganese complexes have been synthesized by the reaction of Mn(CO)5Br with phenanthroline derivatives, which can further react with Na[Re(CO)5] to afford corresponding binuclear complexes (CO)5ReMn(CO)3L (L = 5-aldehyde phenanthroline or 5-carboxylic phenanthroline) (Scheme 1). As expected, such binuclear complexes can exhibit broad MMLCT band centered at much longer wavelength (~600 nm) than the MLCT band of the mononuclear manganese complex at 440 nm. In aerobic solution, these binuclear rhenium-manganese complex releases CO under LED excitation at 659 nm. So this type of binuclear complex can be good candidate serving as photoCORMs. This presentation will discuss these and similar binuclear photoCORMs developed in our laboratory.

Long wavelength light induced CO-release from binuclear rhenium−manganese carbonyl complex

2019 Fall National Meeting

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