Electrochemically Induced Reversible and Irreversible Coupling of Triarylamines

Abstract

The electrochemical coupling and dimerization behavior of the low molecular compounds triphenylamine (TPA) and 9-phenylcarbazole (PHC) in comparison to tri-p-tolylamine (p-TTA) with para-blocked methyl groups has been investigated in detail. In contrast to the unsubstituted radical cations of TPA and PHC, the radical cations of p-TTA are stable in the radical cation state and do not undergo any further coupling reactions. However, we found that the dicationic state of p-TTA does undergo two different competitive reaction pathways: (1) an irreversible intramolecular coupling reaction which leads to phenylcarbazole moieties and (2) a reversible intermolecular dimerization leading to charged σ-dimers. The σ-dimers become decomposed upon discharging at low potentials (E(pc) = -0.97 V vs Fc/Fc(+)) so that the starting monomer p-TTA is partially regenerated. In particular, the reversible dimerization reaction has not been described in literature so far. Polymeric systems containing para-methyl blocked triarylamines in the side chain exhibit similar coupling behavior upon electrochemical doping.

Electronic descriptors for analytical use of the benzidine‐based compounds and the mechanism of oxidative coupling of anilines

“…[1][2][3][4][5] One of the most studied applications is based on usage of the hole-transport materials in thin-layer optoelectronic devices such as xerography, organic light emitting diodes, organic solar cells, and electrochromic devices due to their easy oxidizability and holes transport mobilities up to 10 2 cm 2 V À1 s…”

“…[1][2][3] Basic chemistry of these practical applications is related to the red-ox reactions of N-perarylated aromatic amines, diamines, and triamines. [1,2] After cooling their melts, they generally form amorphous glasses in which charged species, generated by their oxidation, exhibit high stability and high mobility.…”

“…[1][2][3] Basic chemistry of these practical applications is related to the red-ox reactions of N-perarylated aromatic amines, diamines, and triamines. [1,2] After cooling their melts, they generally form amorphous glasses in which charged species, generated by their oxidation, exhibit high stability and high mobility. [4] Meanwhile, N-alkylated amines and diamines, such as N,Ndiethylaniline or N,N,N′,N′-tetraethylbenzidine (Teb), have been recently reported to be effective reagents for colorimetric and visual determination of the ClO À , BrO 3 À , and IO 3 À ions in wastewater.…”

“…[4] Meanwhile, N-alkylated amines and diamines, such as N,Ndiethylaniline or N,N,N′,N′-tetraethylbenzidine (Teb), have been recently reported to be effective reagents for colorimetric and visual determination of the ClO À , BrO 3 À , and IO 3 À ions in wastewater. [5] This method is based on the well-known reaction of electrochemical [1][2][3][4]6] or chemical oxidation of the amines with different oxidants. Among them, the naphthalene-1,8-diylbis (diphenylmethylium) ion, [7] atomic chlorine, [8] and such ions as ClO 4 À , [9,10] Cu 2+ , [9,11] Cr 2 O 7 2À , [10,12] S 2 O 8 2À , [12][13][14] Ti 3+ , [15] Ce 4+ , MnO 4 À -anion [12] were effectively utilized to obtain singly and doubly ionized forms of the aforementioned amines.…”

“…Overall, the latter dications are rather stable-colored species that were comprehensively studied by UV-Vis spectroscopic techniques. [1,2,5,[8][9][10][11][12][15][16][17][18][19][20] In contrast to the vibrational spectra of benzidine (Bzd) and its derivatives, [21] however, any papers containing complete assignment of the absorption spectra of benzidine-based compounds (BBCs) or their singly and doubly ionized forms were appeared in the literature so far. On the other hand, the computational analysis of the absorption spectra will help one to better understand the exceptional stability of these organic dications and to design new reactants for the aforementioned practical applications.…”