Abstract
The synthesis of four symmetrical compounds containing urea/thiourea and anthracene/nitrobenzene groups was optimized. N,N’-Di((anthracen-9-yl)-methylene)thio-carbonohydrazide showed sensitive and selective binding ability for acetate ion among the studied anions. The presence of other competitive anions including F−, H2PO4−, Cl−, Br− and I− did not interfere with the strong binding ability. The mechanism of the host-guest interaction was through multiple hydrogen bonds due to the conformational complementarity and higher basicity. A theoretical investigation explained that intra-molecular hydrogen bonds existed in the compound which could strengthen the anion binding ability. In addition, molecular frontier orbitals in molecular interplay were introduced in order to explain the red-shift phenomenon in the host-guest interaction process. Compounds based on thiourea and anthracene derivatives can thus be used as a chemosensor for detecting acetate ion in environmental and pharmaceutical samples.
Highlights
The artificial design and synthesis of biologically important anion chemosensors has been attracting considerable attention in the field of supramolecular chemistry because of the important roles of various anions in biological, chemical and environmental systems [1,2,3,4,5,6,7,8,9,10,11,12]
Bearing in mind the above considerations, we report in this paper the synthesis of some symmetrical chemosensors based on thiourea derivatives (Scheme 1) and their anion binding ability
The absorption spectra of free 1 displayed an absorption peak centered at 325 nm with a weak shoulder peak at 400 nm, which could be assigned to the intramolecular charge-transfer transitions (ICT) of the thiourea moiety and the excitation of π electrons in the aromatic system, respectively [27,28]
Summary
The artificial design and synthesis of biologically important anion chemosensors has been attracting considerable attention in the field of supramolecular chemistry because of the important roles of various anions in biological, chemical and environmental systems [1,2,3,4,5,6,7,8,9,10,11,12]. The acetate ion and the carboxylate biomolecules may be more important than other biological functions anions. The focus has been mainly on the design a chemosensor which has the ability to bind the biologically important anions. The binding sites in artificial chemosensors are significant and often include amide [17], urea [18], hydroxyl [19,20] and pyrrole [21] moieties due to the strong binding ability to act as hydrogen-bond donors. Anthracene and nitrobenzene were chosen as the fluorogen and chromophore [25,26] because they can act as an optically sensitive indicator for anion binding ability especially for the detection of acetate anion. Bearing in mind the above considerations, we report in this paper the synthesis of some symmetrical chemosensors based on thiourea derivatives (Scheme 1) and their anion binding ability.
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