Fluorescent Chemosensor for Cu2+ based on Schiff base-naphthalene-2-ol

Schiff base-naphthalene-2-ol (L), a novel fluorescent chemosensor, was designed and synthesized. The molecule contains both the Schiff base and hydroxyl as the metal binding sites, and 6-nitronaphthalene moiety as a signaling unit. The binding properties for various cations (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+) of L were examined by using UV-Vis spectrophotometry and Fluorescence spectroscopy. UV-Vis absorption of L selectively bound with Cu2+ at 419 nm was decreased and the absorption at 303 nm was increased after binding, whereas the change of UV-Vis spectra of L in the presence of other cations was not observed. The stoichiometry of the complex was found to be 1: 1 based on the Job plot, and the association constant for L-Cu2+ was determined to be 1.4 x 105 M-1. The quantum mechanical calculations using B3LYP/6-311G(d, p) supported the complexation between L and Cu2+. Addition of Cu2+ showed selective fluorescence quenching of the receptor L in DMSO with the detection limit of 0.65 mu M. The Fluorescence intensity was linearly related with Cu2+ concentration ranging from 0.64-8.57 mu M (r(2) = 0.9941). (C) 2017 Elsevier Ltd. All rights reserved.