Electrochemical oxidation of a hexasulfonated calix[6]arene

The water-soluble calixarene p-hexasulfonato-calix[6]arene 1 was subjected to voltammetric studies of its oxidation. At glassy carbon or platinum electrodes in aqueous electrolyte solutions, oxidation was observed at E > 0.7 V versus SCE in pH 2 solution. On glassy carbon, a stable derivatisation of the electrode surface was inferred from the perturbation in the electrochemistry of the anionic probe species Fe(CN)(6)(3-/4-) while the electrochemistry of the cationic probe Ru(NH3)(6)(3+ 2+) was unchanged. Investigation 6 of the electrochemistry of 1 as a function of pH (2 < pH < 10) showed the expected dependence on the acid -base chemistry of 1 for the derivatisation of the electrode surface. On platinum electrodes, the electrochemical derivatisation was less stable and less obvious than on carbon, indicating a weakly adsorbed modifying layer. (C) 2001 Elsevier Science B.V. All rights reserved.