Calix[4]arenes-based fluorescent chemosensors containing thiosemicarbazone as a binding site and naphthalene as a fluorogenic unit in a 1,3-alternate (L1 ) and cone (L2 ) conformation, were synthesized and examined for their binding abilities towards anions and cations using different spectroscopic techniques. Both receptors L1 and L2 , exhibited an off/on fluorescence behaviour due to complex formation with Cu(II). They showed selective recognition of Cu(II) in presence of other cations and anions detecting up to 4.25 mu g/I. for L1 and 1.58 mu g/I. for L2 , both in acetonitrile. The complexation behaviour was studied by H-1 NMR and FT-IR spectral analysis, indicating that copper interacts with sulphur and with imine nitrogen of the thiosemicarbazone. No major differences in the selectivity and sensitivity were found between calix[4]arene receptors in 1,3-alternate and cone conformation. The H-1 NMR spectra indicates that receptor L2 changed its conformation from cone to pinched cone , stiffening the conformation due to interaction of the thiosemicarbazone moiety with copper. (C) 2020 Elsevier B.V. All rights reserved.