A novel sensing capabilities and structural modification from thiourea to urea derivative by Hg(ClO<sub>4</sub>)<sub>2</sub>: Selective dual chemodosimeter for Hg<SUP>2+</SUP> and F<SUP>-</SUP> ions

Abstract

A new rhodamine-6G phenylthiourea derivative (L1) condensed product was developed as a fluorescent and colorimetric dual chemosensor in acetonitrile with more selective towards Hg2+ and F- ions. Hg2+-promoted spirolactam ring opening of the rhodamine moiety induced urea formation through the diphenylcarbodiimide intermediate from the thiourea moiety. It demonstrates high selectivity for sensing Hg2+ with about 700-fold enhancement in fluorescence emission intensity and micromolar sensitivity (limit of detection 4.52 x 10(-7)M) in comparison with other various metal ions. Hg2+ ions coordinated reversibly to Ll, forming a 1:2 metal-ligand complex. The thiourea moiety provided an anion binding site, and the rhodamine system was responsible for fluorescence. In turn, the chemosensor Ll acted as a selective chemosensor toward F- among various anions. Thus, L1 associated with F- with 1:1 stoichiometry. A recognition mechanism based on the binding modes of Hg-2(+) and F- ions were proved by the analytical techniques like UV-vis, changes in fluorescence, H-1 NMR, FT-IR, ESI-mass and HRMS. In addition, this chemosensor exhibited highly selective and sensitive recognition of azide (N-3(-)) anions upon the addition of Hg2+ with a color change back to colorless in the same solution. (C) 2015 Elsevier B.V. All rights reserved.