Light Response Of Three Water-Soluble Mn-I 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(Me(2)aaz)(CO)(3)]Br (2; where Me(2)aaz = 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 (lambda(385 )and lambda(410)) and thus, act as photoCORMs. The formation of a biscarbonyl intermediate was identified during the photo-release process at lambda(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.