Qingwen Liu’s research while affiliated with Jilin University and other places

Four new D–π–A‐type difluoroboron β‐carbonyl cyclic ketonate complexes that contain carbazole units (TCCH, TCCP, CCH, and CCP) have been synthesized that exhibited reversible mechanofluorochromic (MFC) behaviors. Interestingly, TCCH and TCCP, which contained a tert‐butyl carbazole group, exhibited high‐contrast mechanofluorochromism compared with CCH and CCP, which just contained a carbazole group. For example, shifts of Δδ=49 and 20 nm were detected during the mechanofluorochromism of TCCH and CCH, respectively. We found that tert‐butyl carbazole derivatives existed as isolated molecules in the as‐synthesized crystals, on account of the steric hindrance of the tert‐butyl groups, and that J‐aggregates were formed upon grinding. Transformation between the isolated and aggregated molecules, which was stimulated by mechanical force, led to clear changes in the emission properties. However, J‐aggregates were formed in the as‐synthesized crystals of carbazole derivatives, and grinding only weakened the strength of the π–π interactions, thereby resulting in low‐contrast mechanofluorochromism. Therefore, this approach provides a useful strategy for the design of MFC dyes with high performance.

Amidoxime-modified polyacrylonitrile nanofibrous films (AOPAN NFs) were prepared via an electrospinning technique. The traditional preparation methods for amidoximated polyacrylonitrile (AOPAN) solution were changed and improved. First, the PAN solution was modified by hydroxylamine hydrochloride to produce an AOPAN solution, and then, a small amount of inhibitor was added to the AOPAN solution for electrospinning. We found that the crosslinking of the AOPAN solution was inhibited by the addition of a small amount of inhibitor; at the same time, the storage time of the AOPAN solution was prolonged. In addition, the prepared AOPAN solution was electrospun into nanofibrous films, which could be used as excellent adsorption materials for Cu(II), Pb(II), and methyl orange (MO) after drying. The maximal adsorption capacities for Cu(II), Pb(II), and MO were 143.47, 178.57, and 68.07 mg/g, respectively. The adsorption capacities of the nanofibrous films were more than 50% that of the first adsorption after four recycling runs; this indicated the reusability of the nanofibrous films for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45697.

Palladium-catalyzed C-H direct arylation generally occurs on the ortho-position of directing groups. By comparing meta-arylated products of 2-naphthyl urea to ortho-arylated products of phenyl urea, the ortho- and meta-regioselectivity of aryl ureas were found to depend on the aromaticity of the corresponding aryl substituents. Thus, aromaticity is a new factor which can affect the regioselectivity in C-H direct arylation. The finding was further confirmed by regioselective direct arylation of indole and pyrrole derivatives.

Several novel chiral bifunctional L-thiazoline-thiourea derivatives were easily synthesized from commercially available L-cysteine in high yield. These catalysts were subsequently applied to the enantioselective Michael addition of acetylacetone to β-nitrostyrenes. The products with S configuration were obtained in 98% enantiomeric excess (ee) when the L-thiazoline-thiourea derivatives were used. A plausible transition state model is proposed to explain the observed enantioselectivities. Chirality 00:000-000, 2015. © 2015 Wiley Periodicals, Inc.

In this study, we synthesized a series of 3-triazolo-coumarins and evaluated their antioxidant activities respectively by two methods: trapping 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical(ABTS+·) and oxidation of DNA which was induced by Cu2+/glutathione(GSH), ·OH and 2,2′-azobis(2-amidinopropane hydrochloride)(AAPH). Among the nine 3-triazolo-coumarins, compounds 6c and 6f-6i were synthesized for the first time, which exhibited the capability of terminating radical propagation-chains in oxidation of DNA induced by AAPH. In this study, we found that phenethylamine moiety, hydroxyl and ortho-methoxy are the key groups to enhance the antioxidant activities of compounds. © 2015, Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbH.

Selective meta-arylation of O-β-naphthyl carbamate has been accomplished using Pd(OAc)2 as a catalyst precursor and K2S2O8 with AgOAc as the oxidant. A range of aryl boronic acids could be introduced in moderate to good yields. Mechanistic investigation shows that the carbamate substituent has a unique effect and the reaction undergoes an ortho-carbometallation/meta-direct arylation process.

The insoluble β-cyclodextrin/glutaraldehyde crosslinked polyvinylpyrrolidone nanofibrous membranes were prepared by electrospinning technique. The membranes were extensively characterized by various techniques including attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR), X-ray diffraction(XRD), scanning electron microscopy(SEM) and UV-visible absorption to correlate membrane characteristics with their performance. The adsorption ability of the nanofibrous membranes was tested by performing extraction of Methyl orange(MO) dye in water. It was observed that β-cyclodextrin incorporated in polyvinylpyrrolidone provided the characteristics of high adsorption capacity of polyvinylpyrrolidone. Results of sorption experiments show that the nanofibrous membranes exhibited an adsorption rate of more than 95% for MO and the MO absorbent was 39.82 mg to per gram of β-cyclodextrin glutaraldehyde(β-CDXFM) crosslinked PVP under the optimized experimental conditions.

A multifunctional material with superhydrophobicity, superparamagnetism, mechanical stability and acids–bases resistance was developed from the bead-on-string PVDF and Fe3O4@SiO2@POTS nanoparticles by electrospinning in this work. The Fe3O4@SiO2@POTS nanoparticles which have excellent superparamagnetism were successfully prepared and subsequently introduced into PVDF precursor solution. Through electrospinning, Fe3O4@SiO2@POTS nanoparticles irregularly distributed in the membrane to not only make a dual-scale roughness which is beneficial to obtain a superhydrophobic surface but also stimulate the material turns to superparamagnetic for wider use in different fields. More importantly, the film shows stable superhydrophobicity even for many corrosive solutions, such as acidic or basic solutions over a wide pH range and remarkable mechanical stability. The composition and surface structure of the film are the two critical factors that induce such unusual properties. The weight ratio of Fe3O4@SiO2@POTS/PVDF can strongly influence the superhydrophobicity and mechanical properties of the composite films.

Chiral 1-benzoyl-2-(α-N-substituted aminoethyl)benzimidazoles are successfully applied as nonenzymatic acylating agents for the kinetic resolution of racemic α-amino esters with high enantioselectivity under mild reaction conditions.

Several novel chiral thiazoline primary and tertiary alcohols were easily synthesized from commercially available l‐cysteine in three steps and with high yield. These ligands were subsequently applied to the asymmetric addition of diethylzinc (Et2Zn) to various aldehydes. Products with S configuration were obtained when thiazoline‐containing tertiary alcohol ligands were used as catalysts. The primary alcohol induced corresponding products with R configuration in 68% enantiomeric excess, which was a higher value relative to other N―O ligands possessing a primary alcohol unit in the literature. Furthermore, a plausible transition state model was proposed to explain the observed enantioselectivities. Copyright © 2012 John Wiley & Sons, Ltd.