Dipolar ruthenium(II) ammine complexes as electron transfer mediators of amperometric glucose sensors

The mediation of dipolar ruthenium(II) ammine complexes containing pyridinium ions [Ru(NH3)5(L+)]3+(L+: pyridinium ions) in glucose oxidation has been investigated by a voltammetric method. These ruthenium(II) complexes had appropriate redox potentials of 0.10–0.18 V vs. Ag/AgCl and high ks values of 5.7–17 × 106 M− 1 s− 1 which are the second-order rate constants for electron transfer from glucose oxidase in reduced form to [Ru(NH3)5(L+)]4+. In particular, the ks values for [Ru(NH3)5(L+)]3+ were greater than those of osmium(II)–polypyridine complexes possessing similar redox potentials which are most commonly used. All the dipolar ruthenium(II) complexes used in this study are therefore concluded to be useful for the electron transfer mediators of amperometric glucose sensors.