Experimental and theoretical study of urea and thiourea based new colorimetric chemosensor for fluoride and acetate ions

Two new anion receptors 1,1-(4-nitro-1,2-phenylene) bis(3-phenylurea) (1) and 1,1-(4-nitro-1, 2-phenylene) bis(3-phenylthiourea) (2) have been reported here. The binding and colorimetric sensing properties of receptors I and 2 with different anions were investigated by naked-eye, H-1-NMR and UV-Vis spectroscopy. They showed effective and selective binding with two biologically important anions r and CH3COO-, in presence of other anions, such as Cl-, Br-, I-, NO2-, ClO4-, HSO4-, H2PO4-, CN- in acetonitrile. The relative binding mode of fluoride and acetate anions towards receptors 1 and 2 were studied using density functional theory (OFT), in gas phase and in acetonitrile solvent. Computational studies revealed that receptor 1 formed complexes by two intermolecular hydrogen bonds while receptor 2 by three intermolecular hydrogen bonds. In addition, time dependent DFT (TD-DFT) calculations qualitatively match the experimental UV-Vis spectra. (C) 2015 Elsevier B.V. All rights reserved.