Electrochemical sensing of fluoride and sugars with a boronic acid-substituted bipyridine Fe(II) complex in solution and attached onto an electrode surface

The electrochemical behaviour of a boronic acid-substituted 2,2 ' -bipyridine 1 Fe(II) complex ([Fe(II)1(3)](2+)) has been investigated in aqueous buffered solutions, in the absence and in the presence of F(-) or various sugars as guest species. The binding of the halide to the boron atom led to a shift of the Fe(II)/Fe(III) oxidation peak towards less positive potentials whereas the sugars, and particularly D-fructose, had an opposite effect. With the aim of developing electrochemical sensors, the immobilization of this redox-active receptor onto an electrode surface has been successfully achieved from an electropolymerizable organometallic assembly consisting of the ligand 1 and a N-substituted pyrrole derivative. Its anodic oxidation yielded polymer films which exhibited stable electroactive properties in CH,CN. Owing to the total loss of their electroactivity in aqueous media, only the effect of F(-) on the response of the immobilized Fe(II)/Fe(III) system has been examined in CH,CN. An unusual complexation-induced catalytic phenomenon was evidenced in the presence of this guest anion. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.