A Study of Some Primary Processes in Electropolymerization by Cyclic Voltammetry of Phenyl-Substituted Ethylenes

Abstract

transparent and viscous in contrast with the opaque and solid nature of the amorphous oxide film.The formation of the viscous film, which occurs only in the presence of adequate sulfate concentration, inhibits the evolution of hydrogen and the progress of other reactions that contribute to the formation of the amorphous oxide film. ABSTRACTTetraphenylethylene, triphenylethylene, stilbene, I,I diphenylethylene, and styrene were utilized as model compounds. Cyclic voltammetry in tetrahydrofuran, NBu4C]O4, showed that the radical anions of these compounds were protonated in this medium and are therefore stronger nucleophiles than polycyclic aromatic hydrocarbons for which similar protonation does not occur. The stability of the initial ionic species produced increased with the number of phenyl substituents in this series of substituted ethylenes. The cyclic voltammetric data was examined critically to determine the reversibility of the electron transfer steps, the number of electrons added per step, and the stability or lifetime of transient substances formed. Reaction mechanisms are proposed and the relevance of the findings to electropolymerization processes is indicated.The passage of an electrolytic current through a nonaqueous organic solution can produce a wide variety of reduction products at the cathode. These may include radicals, radical anions, carbanions, and other related intermediates (1).In our previous work, we had shown that in the presence of a suitable monomer, polymerization could take place (2). The rate of polymerization was, in ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.226.37.5 Downloaded on 2015-03-08 to IP 1 0 2 1 PO2 --[3] K 9 acu 4 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.226.37.5 Downloaded on 2015-03-08 to IP

Merostabilization in radical ions, triplets, and biradicals. 6. The excited state behaviour of para-substituted tetraphenylethylenes

“…The electrochemical behaviour of tetraphenylethylene (TPE) has been reasonably well studied with respect to both its oxidation (13) and reduction (14) processes. The oxidative cyclic voltammqgram of TPE in acetonitrile solution exhibits twg closely-spaced separate anodic waves, each corresponding to irreversible one-electron transfer.…”

The electrochemical reduction of triphenylethylene in DMSO: a mechanistic study using mercury hemispherical microelectrodes

“…Reaction schemes corresponding to the proton abstraction of the radical anion [10,11,15,16] and di-anion [11,17] in the presence of proton sources have also been proposed and may operate depending on the degree of basicity of the anion/di-anion species. Other competing pathways have also been proposed including the regeneration mechanism [18] but no clear evidence of their operation has been observed [8,18].…”

“…Of the most relevance to the current study are those literature reports on the electrochemical reduction of tetraphenylethylene (TPE) and triphenylethylene (TriPE) [8,9,11,14,[17][18][19]. The electrochemical reduction of TPE has been studied in dimethylformamide (DMF) [8,14,19], hexamethylphosphoric acid triamide (HMPA) [8] and acetonitrile (MeCN) [11].…”

“…Previous voltammetric studies on the reduction of TriPE have been carried out in aprotic solvents including dimethylformamide (DMF) [8,9,14,18], hexamethylphosphoric acid triamide (HMPA) [8], acetonitrile (MeCN) [11], and tetrahydrofuran (THF) [17]. Voltammetries in DMF and HMPA reveal two successive reduction waves corresponding to separate one electron transfers at the electrode, with reversibility observable only for the first wave.…”

“…It is also generally accepted that the radical anion TriPE ÅÀ is a weak base which is stable towards proton abstraction reactions [8,14,18], therefore, the protonation reaction of TriPE ÅÀ is widely disregarded. The irreversible nature of the second reductive wave has been attributed to rapid protonation of the dianion in the presence of proton sources such as trace water [8,14,17,18].…”