A highly selective fluorescence probe for Co2+ or Cu2+ 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 synthe-sized 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, H-1 NMR,C- 13 NMR, ESI-MS and elemental analysis. Moreover, ion sensing prop-erties 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 Cu(2+ )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 Cu(2+ )and Co2+ ions were estimated to be 0.75 and 0.72 mM, respectively. Besides, stoichiometry, and binding constant in terms of the quenching mechanism were also determined using fluorescence data.(C) 2022 Elsevier Ltd. All rights reserved.