Ferrocene/phenylboronic acid-bearing benzoic acids were prepared to study their electrochemical redox properties in the presence of D-fructose and D-glucose. 4-[N-(2-boronobenzyl)-N-(ferrocenylmethyl)aminomethyl] -benzoic acid (1) exhibited reversible redox response originating from the ferrocene moiety in aqueous solutions containing methanol at pH 7.0, 8.0 and 9.0. The oxidation current of 1 in differential pulse voltammetry (DPV) decreased in the presence of D-fructose and D-glucose, depending on the concentration, owing to the binding of the sugars to phenylboronic acid moiety in 1. The decreased oxidation current may be ascribable to changes in the intra-molecular interaction between the boron and nitrogen atoms in 1. The response of 1 to D-fructose was higher than that to D-glucose because of the higher affinity of D-fructose. The changes in the oxidation current in DPV were observed in the concentration ranges of 1 × 10−3 mol L−1—5 × 10−3 mol L−1 or 1 × 10−3 mol L−1—1 × 10−2 mol L−1 for D-fructose and 1 × 10−3 mol L−1—2 × 10−2 mol L−1 mM for D-glucose. In contrast, 4-[N-(3-boronobenzyl)-N-(ferrocenylmethyl)aminomethyl] benzoic acid (2) showed a negligible response to the sugars, probably due to a lack of intra-molecular interactions between boron atom and nitrogen atom in 2. It may be possible to immobilize 1 on the surface of electrodes because 1 contains the carboxylic acid moiety. Thus, a potential use of 1 in the construction of glucose sensors is suggested.
