Architecture of multi-channel and easy-to-make sensors for selective and sensitive Hg2+ ion recognition through Hg‒C and Hg‒N bonds of naphthoquinone-aniline/pyrene union

Abstract

The aim of this work is, for the first time, to develop new inexpensive, easy-to-make and multi-channel receptors, naphthoquinone-aniline/pyrene union ((Nq-An) and (Nq-Pyr)) and their Hg2+ complexes [Hg-(Nq-An)2] and [Hg-(Nq-Pyr)2] to supply an efficient solution to critical deficiencies to be encountered for Hg2+ recognition. This study is based on colorimetric, fluorometric, and voltammetric methods for determination of Hg2+ ions through Hg-C and Hg-N binding mode of the naphthoquinone-aniline/pyrene union in aqueous media. The binding mode of the receptors with Hg2+ cation was confirmed by usual characterization techniques for the synthesized Hg2+-complexes [Hg-(Nq-An)2] / [Hg-(Nq-Pyr)2] and voltammetric, 1H NMR titration experiments as well as Job's method, indicating a 2:1 complex between the receptors and Hg2+ cation. The receptors showed a considerable color switching from orange to pink along with a red-shift of absorption wavelength, and fluorescence enhancement via the Chelation Enhanced Fluorescence effect (CHEF), and distinctive changes on the voltammogram of the electroactive naphthoquinone unit with Hg2+ cation. The experiments indicate that the sensors are highly selective and sensitive toward Hg2+ among the studied metal ions in aqueous media compared with other reported Hg2+ sensors.