Yong-Bing He

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.

‘Naked‐eye’ enantioselective chemosensors for N‐protected amino acid anions bearing thiourea units

Four linear thiourea anion receptors (1-3) derived from simple amino acid have been synthesized and their bonding properties with various chiral N-protected amino acid anions were examined by using UV-vis and fluorescence titration experiments. Receptors 1a, 2, and 3 exhibit excellent enantioselective recognition abilities towards N-Boc-protected alanine anion in the UV-vis spectra, obvious difference in the color of solution indicate that the enantiomers of N-Boc-alanine anion could be distinguished by naked eye directly. Receptor 1a is also found to carry out enantioselective fluorescent recognition of the N-acetyl-glutamate. (1)H NMR experiments suggest that hydrogen-bonding interaction between the host and guest is the main factor in the recognition process.

Synthesis and Chiral Recognition Properties of Novel Fluorescent Chemosensors for Amino Acid

The charge neutral chiral optical sensors 1a∼d containing thiourea and amide groups were synthesized by simple steps in good yields and their structures were characterized by IR, 1H NMR, 13C NMR, MS spectra and elemental analysis. The enantioselective recognition for α-phenylglycine and phenylglycinol was examined by fluorescence emission and UV-vis spectra. The fluorescence and UV-vis spectra changes of 1a were obvious when the enantiomers of α-phenylglycine anion were added, which exhibited that 1a has good enantioselective recognition ability towards α-phenylglycine.

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.

Chiral Fluorescent Receptors based on Amino Acid Unit: Synthesis and Their Enantioselective Recognition

Three chiral fluorescent receptors (1, 2 and 3) were synthesized and their structures were characterized by IR, 1H NMR, 13C NMR, MS spectra and elemental analysis. The enantioselective recognition of receptors 1, 2 and 3 were studied by fluorescence spectra and 1H NMR spectra. The results demonstrate that receptors 1, 2 and 3 with the N-Boc-protected phenylalanine anion formed a 1:1 complex. The receptor 3 exhibits good enantioselective recognition ability toward the enantiomers of the N-Boc-protected phenylalanine anion.

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.

Synthesis and Chiral Recognition Properties of a Novel Colorimetric Chiral Sensor for Carboxylic Anions

Chiral colorimetric sensor 4 has been synthesized, and the structure characterized by IR and 1H NMR spectroscopy, mass spectrometry, and elemental analysis. The chiral recognition of the receptor was studied by 1H NMR and UV-vis spectroscopy. The results of non-linear curve fitting indicate that the receptor 4 and l- or d-mandelate and alanine anions form a 1:1 stoichiometric complex. The obvious colour change of receptor 4 can be observed by the naked eye when the enantiomers of mandelate and alanine anions are added, which demonstrates that receptor 4 may be used as the colorimetric sensor for the two carboxylic anions.

Enantioselective Fluorescent Recognition of Amino Alcohol Based on Calix[4]arenes Bearing Diphenylethylenediamine Units

Two novel chiral fluorescence calix[4]arenes functionalized at the lower rim with diphenylethylenediamine and thiourea units were synthesized and examined for their enantioselective recognition abilities by the fluorescence and 1H NMR spectra in DMSO. The results indicate that 1 and 2 both formed a 1:1 complex with amino alcohol and exhibit good enantioselective fluorescent responses for phenylglycinol (receptor 1 K L/K D = 4.85, ΔΔG0 = − 3.90 kJ mol− 1).