ELECTROCATALYTIC ACTIVITY OF [(BPY)2(H2O)RUIIIORUIII(H2O) (BPY)2]4+ TOWARDS SUGAR OXIDATION

The oxo-bridged dinuclear cation [(bpy)2(H2O)Ru(III)ORu(III)(H2O)(bpy) 2]4+ (1) (bpy = bipyridine), when oxidized to the Ru(IV)Ru(V) oxidatio n state, is an effective catalyst for the oxidation of a series of sug ars with acetalic structure, like methyl-alpha-D-glucopyranoside (MGP) , methyl-alpha-mannopyranoside (MMP), phenyl-beta-D-glucopyranoside (P GP) and octyl-alpha-D-glucopyranoside (OGP). Cyclic voltammetry was ap plied to study the reactivity of 1 in basic solution towards oxidation of MGP, MMP and PGP. The electrogenerated Ru(IV)Ru(V) form of 1 oxidi zes MGP, MMP, PGP, ethanol and 2-propanol in reactions that are first- order both in catalyst and in substrate. The second-order rate constan t, K(cat) for the oxidation of MGP, MMP, PGP, ethanol and 2-propanol i n 1 M NaOH, are 16.1 +/- 0.4, 35.0 +/- 1.0, 26.8 +/- 0.4, 16.0 +/- 1.0 , and 6.6 +/- 0.7 M-1 . s-1, respectively, Bulk electrolysis of 1 in 0 .1 M NaOH in presence of MGP, or OGP, was carried out with the purpose of identifying the carbohydrate oxidized products. HPLC analyses of t he MGP and OGP oxidation mixtures after electrolysis revealed that in both cases the only oxidized products are the corresponding alkyl gluc uronides.