Lingzhi Meng

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.

New type chiral calix[4](aza)crowns: synthesis and chiral recognition

Two new types of chiral calix[4](aza)crowns containing l-valine were synthesized by the reaction of calix[4]arene diacid dichloride with the corresponding chiral diamines derived from C2-symmetric chiral disulfonamides. Preliminary application of one ligand in chiral recognition was studied by 1H and 13C NMR, and UV spectroscopy.

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−.

The Effects of Intramolecular Hydrogen Bonding on the Reaction of Phenols with Epoxide in the Presence of Nano Calcium Carbonate

The reaction of phenols and dihydroxybenzenes with epoxide in the presence of nano CaCO3 was studied. Catechol could react with epoxide and gave monochlorohydrin derivative; other dihydroxybenzenes and monomeric phenols had no reaction under the same conditions. The reaction of catechol with epoxide did not occur when nano CaCO3 was replaced by a normal one. These were attributed to the strong interaction between nano CaCO3 and the substrate as catechol possessed intrahydrogen bond and excess active hydrogen, which can induce the intramolecular proton transfer via the intramolecular hydrogen bond and promote the reaction of hydroxyl and epoxide. This is an example revealing the unique role of the hydrogen bond played in chemical reactions.