Synthesis of new chromogenic sensors containing thiourea and selective detection for F^–, H₂PO₄^–, and Ac^– anions

Abstract

Two new chromogenic sensors 1-(2-hydroxyphenyl)-3-(4-nitrophenyl)thiourea 1 and 1-(3-hydroxypyridin-2-yl)-3-(4-nitrophenyl)thiourea 2 bearing nitrophenyl and thiourea groups were designed and synthesized by one-step procedure and characterized through 1 H NMR, 13 C NMR, FTIR, and MS. The anion recognition property of the receptors was studied via naked-eye detection, UV–vis, and 1 H NMR. Based on the existence of amino gen and hydroxyl moieties in receptors, receptors 1 and 2 exhibit obvious selectivity by the redshift of UV–vis signals, colour changes through naked-eye detection, and binding effects for F – , H 2 PO 4 – , and Ac – . Surprisingly, the detection limits of receptor 1 for F – and Ac – were calculated to be 5.45 × 10 −7 and 2.11 × 10 −7 (mol/L) −1 , respectively, which indicated that F – and Ac – can be identified with high sensitivity by receptor 1. Besides, simple “test strips” were developed and were used as sensors for recognition of F – , H 2 PO 4 – , or Ac – in DMSO solution. Lastly, the mechanisms of the recognition process were studied through DFT calculation and 1 H NMR titration.