Polarographische Untersuchungen an symmetrischen Triazacarbocyaninen in Acetonitril

Abstract

The reduction behaviour of thirteen symmetrical triazacarbocyanine dyes with different heterocycles in acetonitrile solution has been investigated by means of dcand ac-polarography, cyclic oscillopolarography and coulometry.The reduction mechanism has been found to be of the type eec with the first step being reversible and the second step being reversible to irreversible. Reduction potentials, transfer coefficients and specific currents of both steps have been measured (Ell2: -0,110 to -1.025 V vs. Ag/AgCl for the first step) and compared with known properties of carbocyanines and triazenium salts and to HMO calculations.The effect of substituents X has been studied on the compounds 1,3-diethyl-2-[( 1,3-diethyl-5 -Xbenzimidazolin-2-yliden)triazenyl] -5 -Xbenzimidazoliumtetrafluoroborate (1 a (X)) and 3 -ethyl-2 -[(3 -ethyl-5 -X-d4-1,3-triazolin -2 -y1iden)triazenyll-5-X-1,3-thiazolium-tetrafluoroborate (1 g (X)), and p-values of 0,36 and 0,72 V, respectively, have been found.Einleitung. -In den letzten 20 Jahren sind zahlreiche Arbeiten iiber das elektro-