Jian-Xin Zhang

Host–guest interactions of thiabendazole with normal and modified cucurbituril: 1H NMR, phase solubility and antifungal activity studies

Guest–host inclusion complexes between thiabendazole (TBZ) and cucurbit[7]uril (Q[7]), symmetrical tetra-methylcucurbit[6]uril (TMeQ[6]) and meta-hexamethyl-substituted cucurbit[6]uril (HMeQ[6]) in aqueous solution were investigated by 1H NMR spectroscopy and phase solubility studies. The antifungal activities of the inclusion complexes were also determined. Analysis of the 1H NMR spectra revealed that the host Q[7] selectively binds the benzimidazole ring moiety of the guest molecule and that the thiazole ring is encapsulated into the cavities of TMeQ[6] and HMeQ[6]. Phase solubility diagrams were analysed using rigorous procedures to obtain estimates of the complex formation constants for Q[n]-TBZ complexation. The phase solubility studies showed that TBZ solubility increased as a function of Q[7], TMeQ[6] and HMeQ[6] concentrations. We found that complexation of TBZ with Q[n] increased the inhibitory effect of TBZ on the growth of Fusarium graminearum. Our results thus demonstrate that complexation of TBZ with Q[n] could be used to improve the solubility and antifungal activity of TBZ.

A host–guest complexation based fluorescent probe for the detection of paraquat and diquat herbicides in aqueous solutions

The supramolecular interactions among thioflavin T (ThT), two herbicides paraquat (PQ) and diquat (DQ), and macrocyclic cucurbit[8]uril (Q[8]), were studied using spectrofluorimetry, ultraviolet-visible absorbance spectrometry, 1H nuclear magnetic resonance spectroscopy, and isothermal titration calorimetry. A new method based on fluorescence quenching of the fluorescent host–guest complexes of Q[8]–ThT (the probe) upon cooperative binding with PQ or DQ to form a ternary complex, was proposed for the analytical determination of the two herbicides in aqueous solutions. Detection limits of 7.95 × 10−9 mol L−1 and 8.07 × 10−9 mol L−1 were obtained for PQ and DQ, respectively. Recoveries obtained by the proposed method in real-world examples such as river water and cabbage extracts were 104–108%. Interestingly, this method demonstrated high selectivity towards PQ and DQ in the presence of various metal ions and quaternary ammonium substances. Such a method provides a rapid, selective, sensitive and facile strategy for herbicides detection and quantification.

Synthesis and fluorescence properties of a 1,3-disubstituted thiacalix[4]arene crown-5 armed with phenothiazine moieties

A new thiacalix[4]arene phenothiazine derivative (2) based on a thiacalix[4]crown with a 1,3-alternate conformation has been synthesized and characterized. In THF-water mixture, Compound 2 exhibits a strong fluorescence emission, with a large Stokes shift (λex/em = 357 nm/505 nm, Δλ = 148 nm), which helps to avoid interference in excitation and emission. For the metal ions tested, the fluorescence of Compound 2 was quenched only by Fe3+ and Cr3+ ions. Evidence for the hydrolysis reaction promoted by the metal ions is given by X-ray crystallography, mass spectra (MS), infrared (IR) spectra, and fluorescence spectroscopy data.

Direct synthesis of cucurbit[5]uril-anchored polyacrylic acid microspheres and potential applications in selective sorption

A one-pot strategy was employed to synthesize a series of cucurbit[5]uril-anchored (Q[5]-anchored) polymers with high yields. The acrylic acid (AA) monomer, an ammonium persulfate salt (APS) initiator, and an oxidant were used in the polymerization. The Q[5]-anchored polyacrylic acid aggregates (Q[5]-PAA) have been characterized by 1H NMR, 13C NMR, 2D NMR, FTIR, TGA, GPC, TEM and SEM measurements. The experimental results confirm that PAA chains can be grafted to Q[5] in a controlled manner through an in situ radical polymerization approach. The effects of acrylic acid and Q[5] feed mass and APS concentration on the formation of polymer nanocapsules have been investigated. The experiments reveal that the feed mass of acrylic acid greatly influences the properties of Q[5]-PAA when the ratio of Q[5]/APS is fixed at 0.5. In particular, when APS/Q[5] = 46 and 72, vesicle structures are observed in the Q[5]-anchored polymers. Moreover, such polymer nanocapsules show selective absorption of some volatile compounds, particularly methanol.

Direct syntheses of cucurbit[7]uril-anchored polyacrylic acid microspheres and adsorption of basic dyes by the derivative

A one-pot strategy was employed to synthesize a series of water-soluble cucurbit[7]uril-anchored polyacrylic acids (Q[7]-anchored PAAs) with high yields in the presence of an ammonium persulfate salt as both an initiator and an oxidant. The effects of acrylic acid, Q[7] feed mass and APS concentration on the formation of polymer nanocapsules have been investigated. The Q[7]-anchored PAAs can be further esterified with 2-naphthol to yield water-insoluble derivatives, which are characteristic of the stationary phase for absorption of basic dyes, especially neutral red.