Electrochemical study of tris(4-bromophenyl)amine and 2,2,6,6-tetramethylpiperidine-1-oxyl in room-temperature ionic liquids

The electrochemical behavior of tris(4-bromophenyl)amine (TBPA) and 2 2 6 6-tetramethylpiperidine-1-oxyl (TEMPO) was comparatively studied in room temperature ionic liquids (RTILs) containing 1-butyl-3-methylimidazolium cation [BMIm](+) and the anions BF4- PF6- and CF3SO3- TEMPO showed a well-defined electrochemical reversibility with anodic to cathodic peak current ratio (I-a/I-c) equals to unity in all RTILs at a glassy carbon electrode In contrast I-a/I-c ratio greater than unity was observed at all scan rates employed (10-1000 mVs(-1)) in cyclic voltammograms (CV) of TBPA in RTILs Controlled-potential bulk electrolysis of TBPA in RTILs yielded a dark blue colored solution of monocation TBPA (+) which is stable under nitrogen Diffusion coefficient of TBPA cation was determined in all three ILs by chronoamperometry and found to be at least one order of magnitude less than the calculated value of TBPA This effect in conjunction with the deviation of the I-a/I-c ratio from unity could be ascribed to ion-pairing interaction between the TBPA (+) cation and the anion of the RTILs (C) 2010 Elsevier Ltd All rights reserved