Synthesis, electrochemical, and spectroelectrochemical properties of tetrakis(13,17-dioxa nonacosane-15-sulphanyl) phthalocyaninato zinc(II)

Abstract

Tetrakis(13,17-dioxa nonacosane-15-sulphanyl) phthalocyaninato zinc(II), ZnPc(SCH(CH 2OR) 2) 4, where R = C 12H 25, was synthesised and its electrochemical and spectroelectrochemical properties were investigated in dichloromethane. The neutral complex undergoes two quasi-reversible one-electron oxidations and two quasi-reversible one-electron reductions in CH 2Cl 2 containing 0.1 M tetra- n-butylammonium perchlorate (TBAP). The half-wave potentials for oxidation of the complex are located at E 1/2 = 0.61 and 1.38 V, while the two reductions are located at E 1/2 = −0.87 and −1.11 V versus SCE. These potentials show little or no difference compared to those of unsubstituted ZnPc and other SR substituted phthalocyanines under the same experimental conditions, thus suggesting weak electron-donating effects of the peripheral alkylthio substituents on the phthalocyanine rings. The well-defined UV–Vis spectra of electro-reduced and electro-oxidised species, [ZnPc(-3)(SCH(CH 2OR) 2) 4] −, [ZnPc(-4)(SCH(CH 2OR) 2) 4] 2− and [ZnPc(-1)(SCH(CH 2OR) 2) 4] +, were obtained by applied potentials ( E app = −1.04 V, E app = −1.62 V, and E app = 1.20 V, respectively) in a thin-layer cell. The first and second reduction products showed characteristic spectral changes corresponding to mono- and di-anionic species of zinc phthalocyanines, and the first oxidation showed spectral changes corresponding to the formation of a mono-cationic dimer.