The electrochemical behaviour of Para-Sulfonatocalix[4]arene ions in the presence of ionic liquids as supporting electrolyte

Abstract

The electrochemical behaviour of sodium p-sulfonatocalix[4]arene (s-psc4) was studied. In this study ionic liquid/water mixtures were used as electrolyte, namely, [BMIM][BF4]/water mixture and [BMIM][OTf]/water mixture ([BMIM] = 1-butyl 3-methyl imidazolium, BF4 = tetrafluoroborate, OTf = trifluoromethanesulfonate). Spsc4 can be oxidised at 0.84 V and 0.83 V in [BMIM][BF4]/water and [BMIM][OTf]/water respectively. The reaction is an irreversible process for both systems. The number of electron transferred in this electrochemical process is one electron and the diffusion coefficient, (D) for both systems was 1.15 x 10-8 cm2 s-1 and 1.67 x 10-8 cm2 s-1 respectively. The anodic potentials were affected by temperature and the activation energy, (Ed) was 18.18 kJ mol-1 and 18.78 kJ mol-1 in [BMIM][BF4]/water mixture and [BMIM][OTf]/water mixture respectively. Sodium ion, (Na+) on s-psc4 has been replaced with bigger ion, N1444 + (tributyl ammonium ion) in order to fully dissolve it in pure ionic liquid. The electrochemisty of the prepared calixarene namely, (N1444)SO3calix[4]arene, was done in pure ionic liquid, [BMIM][BF4]. Two oxidation peaks were observed at 0.20 V and 1.20 V and were assigned as the oxidation of phenolate and phenol ion.