ELECTROCHEMICAL RECOGNITION OF ALKALI-METAL CATIONS BY ELECTRODES MODIFIED WITH POLY[TRIS-(2,2'-BIPYRIDINE) RUTHENIUM(II)] FILMS

The electrochemical behavior of tris-substituted bipyridine ruthenium (II) complexes containing the aza-crown-substituted 2,2'-bipyridine li gands L-2 and L-3 (L-2 is 4,4'-disubstituted by 1-aza-18-crown-6 moiet ies; L-3 is bridged at its 4,4'-positions by a 4,13-diaza-18-crown-6 g roup), has been studied by cyclic voltammetry in acetonitrile electrol yte, and in the presence of alkali metal cations (Li+, Na+, K+). Cycli c voltammetry curves show that these complexes are able to recognize p otentiometrically a metal cation. The L-2-based complex is sensitive t o Li+ and Na+ cations, while the L-3-based complex is only sensitive t o the presence of potassium ions. Glassy carbon electrodes have been m odified by electropolymerization of the related complexes containing p yrrole-substituted bipyridine ligands. The electrochemical behavior of the resulting redox-active films in the presence of the surveyed alka li metal cations shows that the electrochemical recognition properties of these complexes are mainly retained after their immobilization ont o an electrode surface, which is a prerequisite to the construction of new prototypes of electrochemical sensor. (C) 1998 Elsevier Science L td. All rights reserved.