Calcium Ion−Calixquinone Complexes Adsorbed on a Silver Electrode

The structures and redox-switching behavior of Ca2+/calix[4]quinone complexes on a Ag surface were investigated by reflection−absorption infrared spectroscopy (RAIRS), Monte Carlo simulation, and voltammetry. RAIRS and Monte Carlo simulation show that the carboxylate groups of calix[4]arene-triacid-monoquinone (CTAQ) and calix[4]arene-diacid-diquinone (CDAQ) are involved in not only binding with the Ca2+ ions but also spontaneous adsorption of their complexes onto the Ag surface. According to the RAIRS results, the Ca2+ ions in the complexes lie in vicinity to the quinone moieties. Monte Carlo simulation provides more detailed information about the probable conformations of the Ca2+/calix[4]quinone complexes adsorbed on the Ag surface. Voltammetric behavior is consistent with the RAIRS and Monte Carlo simulation results and shows the effect of Ca2+ ions to the redox processes of the CTAQ- or CDAQ-modified Ag electrodes.