Electrochemistry of a Double-Decker Lutetium(III) Phthalocyanine in Aqueous Media. The First Evidence for Five Reductions

Abstract

The double-decker lutetium(III) phthalocyanine, Lu[(RS)4Pc]2, where R = C12H25, was synthesized and electrochemically characterized under several solution conditions. The neutral complex undergoes a single reversible one-electron oxidation and up to four reversible one-electron reductions in nonaqueous solutions of CH2Cl2 or benzonitrile containing 0.1 M tetra-n-butylammonium perchlorate (TBAP), while one oxidation and five reductions are seen in aqueous 0.5 M KCl for a gel-like cast film membrane of Lu[(RS)4Pc]2 in a tetraoctylphosphonium bromide (4C8P+Br-) matrix at a basal plane pyrolytic graphite electrode. The half-wave potentials for reduction of Lu[(RS)4Pc]2 in CH2Cl2, 0.1 M TBAP are located at E1/2 = 0.04, −1.03, −1.36 and −1.73 V, while the single oxidation is located at E1/2 = 0.43 V vs SCE. These potentials, when measured vs Fc/Fc+, are negatively shifted by 0.20−0.46 V from the E1/2 values obtained in the 0.5 M KCl solution where the electrogenerated anions of the double-decker complex are sta...