Lan-Hua Wei

Calix[4]arenes containing thiourea and amide moieties: neutral receptors towards α,ω-dicarboxylate anions

Two-armed neutral anion receptors (4, 5), were prepared and examined for their anion-binding ability using UV-vis, fluorescence and 1H NMR spectra in DMSO. The results of non-linear curve fitting indicate that 4 or 5 form 1 : 1 stoichiometric complexes with dicarboxylate anions by multiple hydrogen bonding interactions and the sensitivity for recognition of dicarboxylate depends on the chain length of these dicarboxylate anions. Receptors 4 and 5 have no binding ability with acetate, dihydrogen phosphate and the halogen (Cl−, Br−, I−) anions. This demonstrates that receptors 4 or 5 could be used as chemical sensors for some special dicarboxylate anions.

Two Thiourea-based Colorimetric Sensors for Anions: Structure and Binding Study

Two colorimetric thiourea-based chemsensors with two relatively rigid arms, 2A and 2B, were synthesized. Their binding abilities with halide anions, AcO−, [Formula: See Text] were studied by UV-Vis spectroscopy in DMSO. The two sensors showed a notable selective color response to F− anion from colorless to green-yellow in recognition. The structures of the two sensors and their binding behaviors are discussed. The association constants were calculated by nonlinear fittings of 1:1, 1:2 or 1:1 to 1:2.

Anionic Fluororeceptors based on Thiourea and Hydrazide: Synthesis and Recognition Properties

Two new neutral receptors (1 and 2) containing thiourea and hydrazide groups were synthesized by simple steps in high yields. The binding properties of 1 and 2 for various anions were characterized by UV–Vis and fluorescence spectra. Receptor 1 had a good selectivity for AcO- in comparison with other anions. The association constants of 1·AcO- and 2·p-NO2PhO- were greater than those of other anions ( Cl-, Br- and I-). In particular, an obvious color change from light yellow to orange–red was observed upon addition of AcO- to the solution of 1 in DMSO. The results of nonlinear curve fitting by fluorescence spectral data indicate that a complex of 1:1 stoichiometry is formed between compound 1 or 2 and the anions through hydrogen-bonding interaction.

A Multi-armed Neutral Receptor for α,ω-Dicarboxylate Anions

A multi-armed neutral anion receptor (1) bearing multiple amide and thiourea binding sites was synthesized. Receptor 1 forms 1:2 complexes with dicarboxylate anions, and the sensitivity for recognition of dicarboxylate depends strongly on the chain length of these dicarboxylate anions. Addition of the anions caused a considerable change in the absorbance and fluorescent intensity of the host solution and a consequent visible color change.

A New Two-Armed Colorimetric Chemosensor for Fluoride

The neutral anion receptor 1 was synthesized by an easy method with high yield. The binding properties of anions with 1 were examined by UV-vis and 1H NMR spectroscopy. Receptor 1 can form a 1 : 2 complex with F−, and 1 : 1 complexes with AcO− and H2PO4− anions, respectively, by multiple hydrogen-bonding interactions. There is an observable colour change for the complex formed by 1 and F−.