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.