A highly selective fluorescence probe for Co2+ or Cu2+ detection based on a new tetraquinoline-substituted calix[4]arene derivative

Abstract

A new calixarene derivative (AlQuin-Calix) bearing two quinoline groups at its lower rim was synthesized at cone conformation. Then, upon functionalization of AlQuin-Calix with two more quinoline groups resulted with a novel calixarene-based fluorescent chemosensor (TetQuin-Calix) at partial cone conformation. The structures of all calixarene derivatives were duly characterized by spectroscopic methods such as FTIR, 1H NMR, 13C NMR, ESI-MS and elemental analysis. Moreover, ion sensing properties of AlQuin-Calix and TetQuin-Calix against different cations such as Co2+, Cu2+, Ni2+, Zn2+ and Ba2+ were evaluated. It was found that the calixarene-based chemosensor (TetQuin-Calix) exhibits remarkable affinity and high selectivity for Cu2+ and Co2+ in 50% water-CH3CN, while AlQuin-Calix provides an efficient chemosensor property towards only Co2+ ion among others. The fluorescence of TetQuin-Calix, with excitation/emission peaks at 268/397 nm, is quenched by Cu2+ or Co2+ ions. The limits of detection of TetQuin-Calix for Cu2+ and Co2+ ions were estimated to be 0.75 and 0.72 μM, respectively. Besides, stoichiometry, and binding constant in terms of the quenching mechanism were also determined using fluorescence data.