Highly selective and sensitive fluorescent sensor: Thiacalix[4]arene-1-naphthalene carboxylate for Zn2+ ions

Abstract

Thiacalix[4]arene based fluorescent sensor bearing two naphthoyl groups, thiacalix-1-naphthalene carboxylate (TCNC) has been synthesized and characterized by 1H NMR, 13C NMR, FTIR, ESI-MS spectroscopic techniques. The interaction behavior of TCNC with various metal ions like Fe3+, Hg2+, Co2+, Ni2+, Cu2+, Cd2+, Pb2+, Mg2+, K+, Na+, and Zn2+ was studied by UV-visible and emission spectrophotometry. It was observed that TCNC recognizes Zn2+ ions with high selectivity and sensitivity. The enhancement of fluorescence intensity due to presence of Zn2+ ions was not perturbed in the presence of high concentration of other associated metal ions. The 1:1 stoichiometry of TCNC:Zn2+ complex was confirmed by job's plot, ESI-MS study and 1H NMR titration. The binding constant and quantum yield were also calculated by using spectrofluorimetric titration data. Linear detection range of zinc ions was found to be 1 nM–740 nM. Furthermore, molecular docking study was performed to evaluate the binding affinity and possible interactions between TCNC and Zn2+ depicting that TCNC interact with Zn2+ via weak intramolecular forces. In addition to that molecular dynamics has also been performed to evaluate the conformational changes and it's structural stability in the particular environment.