Spectrophotometric kinetic study and analytical implications of the glucose oxidase-catalyzed reduction of [M-III(LL)(2)Cl-2](+) complexes by D-glucose (M = Os and Ru, LL = 2,2 '-bipyridine and 1,10-phenanthroline type ligands)

Glucose oxidase-catalyzed reduction of cis[M-III(LL)(2)Cl-2](+) (M = Os and Ru) complexes to cis[M-II(LL)(2)Cl-2] (LL=2,2'-bipyTidine and 1,10-phenant hroline type ligands) by D-glucose is a first-order process in the complex and the enzyme in aqueous buffered solution. The reaction follows Michaelis -Menten kinetics in D-glucose and the rate is independent of D-glucose conc entration above 0.03 M. The reactivity decreases in the series [Ru(bpy)(2)C l-2](+) > [Os(phen)(2)Cl-2](+) > [Os(4,4'-Me(2)bpy)(2)Cl-2](+) > [Os(4,7-Me (2)phen)(2)Cl-2](+). The measured second-order rate constant for the oxidat ion of reduced glucose oxidase by [Os(phen)(2)Cl-2](+) in air equals 1.2 x 10(5) M-1 s(-1) at pH 6.7, [D-glucose] 0.05 M, and 25 degrees C, which is c a. 20% less than that when the reaction solutions are purged with argon. In the case of [Ru(bpy)(2)Cl-2](+) the rate constant equals 1.8 x 10(5) M-1 s (-1) under similar conditions in air, showing higher reactivity of Ru compl exes compared with Os ones. The reduction is pH-dependent with a maximum ar ound 7. Added for solubilization of poorly soluble metal complexes, surfact ants decrease the rates of the enzymatic reaction. The retardation effect i ncreases in the series: cetyltrimethylammonium bromide < Triton X-100 much less than sodium dodecyl sulfate, i.e. on going from positively charged to neutral and then to negatively charged surfactants. The behavior of the Os- III and Ru-III complexes toward reduced glucose oxidase contrasts to that o f recently studied ferricenium cations. As opposed to the latter, the forme r do not show kinetically meaningful binding with the enzyme, and the Micha elis kinetics typical of the ferricenium case is not realized for the Os-II I, and Ru-III species. The systems Os-III- or Ru-III-glucose oxidase are co nvenient for routine "one pot" spectrophotometric monitoring of the D-gluco se content in samples, since the metal reduction to M-II is accompanied by a strong increase in absorbance in the visible spectral region.