Light Response of Three Water-Soluble MnI PhotoCORMs: Spectroscopic Features and CO Release Investigation

Currently, there is great interest in the study of water-soluble metal compounds capable of releasing carbon monoxide, due to their potential therapeutic use. This paper reports the synthesis, spectroscopic characteristics and CO release properties of three water-soluble manganese(I) carbonyl compounds [Mn(aaz)(CO)3]Br (1; where aaz = 6-amino-6-methylperhydro-1,4-diazepine), [Mn(Me2aaz)(CO)3]Br (2; where Me2aaz = 6-amino-1,4,6-trimethyl-1,4-diazacycloheptane) and [Mn(tacn)(CO)3]Br (3; where tacn = 1,4,7-triazacyclononane), that can act as photoCORMs (where CORM is carbon monoxide-releasing molecule). The main aim was to propose a mechanism for the CO release. Compounds 1-3 are capable of releasing carbon monoxide when exposed to light ( λ 385 and λ 410) and thus, act as photoCORMs. The formation of a biscarbonyl intermediate was identified during the photo-release process at λ 385 and the quantum yields and rates of CO release were determined. The proposed CO release mechanisms involve two steps, where photo and redox processes take place, and compounds 1 and 2 exhibit a slightly different mechanism from compound 3. A good understanding of the CO photo-release mechanism is very important with regard to the development of more efficient compounds, particularly those intended for medical applications.
Source: Journal of the Brazilian Chemical Society - Category: Chemistry Source Type: research