Functionalization of calix[4]arene with amidofluorene moieties at the lower rim led to formation of the 1,3-diconjugate of calix[4]arene L as a novel fluorescent chemosensor for Cu2+. The receptor molecule L exhibited a pronounced selectivity towards Cu2+ over other mono and divalent ions. The formation of the complex between L and Cu2+ was evaluated by absorption, fluorescence and 1H NMR spectroscopy. The sensor L showed a remarkable color change from colorless to purple and a fluorescence quenching only upon interaction with Cu2+. The 1:1 stoichiometry of the obtained complex has been determined by Job’s plot. The association constant determined by fluorescence titration was found to be 1.8 × 106 M−1. The sensor showed a linear response toward Cu2+ in the concentration range from 1 to 10 μM with a detection limit of 9.6 × 10−8 M.
