New Cobalt Complex with Dihydroxycoumarin: Synthesis and Kinetics of Its Redox-Activated Dissociation

A new redox-active cobalt(III) complex containing the 2-oxo-2Н-chromene-6,7-diolate dianion and 4,4'-dimethoxy-2,2'-bipyridine as ligands is synthesized. The reduction of the synthesized complex with ascorbic acid in an inert atmosphere is studied in situ by NMR spectroscopy. The reduction is shown to result in the release of 6,7-dihydrocycoumarin acting as a model drug. This process has the first order with respect to the initial complex.