Electrochemical analysis of the coordination sphere of ruthenium(ii) as electron transfer mediator in glucose oxidase catalysis in aqueous solutions

The redox potentials of the cis-Ru(LL)₂XY]ⁿ⁺ complexes (LL = 2,2"-bipyridyl (bpy), 1,10-phenanthroline (phen), and 4,4"-dimethyl-2,2"-bipyridyl (Me₂bpy); X, Y = Cl^–, Br^–, CO₃ ^2–, NO₂ ^–, SCN^–, N₃ ^–, H₂O, and DMSO) in aqueous buffer solutions were measured and analyzed in the framework of the Lever theory on the additivity of contributions of ligands (E _L) to the apparent redox potential of the complex (E ^o"). The complexes manifest the properties of reversible or quasireversible redox systems, whose formal redox potentials lie in the 0.2—0.5 V range. The complexes are efficient electron transfer mediators between the active center of glucose oxidase (GO) from Aspergillus niger and an electrode.