A highly selective fluorescence probe for Co 2+ or Cu 2+ detection based on a new tetraquinoline-substituted calix[4]arene derivative

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, 1 H NMR, 13 C NMR, ESI-MS and elemental analysis. Moreover, ion sensing properties of AlQuin-Calix and TetQuin-Calix against different cations such as Co 2+, Cu 2+, Ni 2+, Zn 2+ and Ba 2+ were evaluated. It was found that the calixarene-based chemosensor ( TetQuin-Calix ) exhibits remarkable affinity and high selectivity for Cu 2+ and Co 2+ in 50% water-CH 3 CN, while AlQuin-Calix provides an efficient chemosensor property towards only Co 2+ ion among others. The fluorescence of TetQuin-Calix, with excitation/emission peaks at 268/397 nm, is quenched by Cu 2+ or Co 2+ ions. The limits of detection of TetQuin-Calix for Cu 2+ and Co 2+ 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.