Yunpu Wang

Amino acid Schiff base complex catalyst for effective oxidation of olefins with molecular oxygen

Abstract The amino acid Schiff base manganese complex (Sal–Phe–Mn) was prepared with l -phenylalanine, salicylaldehyde and Mn(OAc) 2 ·4H 2 O. The ligand and the complex were characterized by the infrared spectra, small area X-ray photoelectron spectroscopy, and ICP-AES. In the presence of the manganese complex, cyclohexene was effectively oxidized by molecular oxygen without reductant. The major products of the reaction were 2-cyclohexen-1-ol (–OH), 2-cyclohexen-1-one (CO) and 2-cyclohexen-1-hydroperoxide (–OOH), which was different with typical oxidation of cyclohexene. The influence of reaction temperature and additive for oxidation had been studied. The selectivity of 2-cyclohexen-1-hydroperoxide varied with reaction time and different additives. The mechanism of cyclohexene oxidation had also been discussed.

Structure-antioxidant relationships of sulfated galactomannan from guar gum.

Sulfated polysaccharides exerted potential biological property which was relative to degree of sulfation (DS), M(w), substitution position and chain conformation. In the present study, commercial guar gum was purified and its sulfated derivates with different DS and M(w) were synthesized. FT-IR and 13C NMR analysis indicated that C-6 substitution was predominant in sulfated samples compared with other positions. In the sulfation reaction, a sharp decrease in M(w) was observed. The d(f) values from 1.92 to 2.85 indicated that the -SO3H groups led to the relatively expanded conformation of sulfated polysaccharides. Antioxidant assays showed that sulfated polysaccharides had better antioxidant activities. The data obtained in in vitro models indicated that high DS and low M(w) showed the best antioxidant capacities.

Fluorescence properties of ternary complexes of polymer-bond triphenylphosphine, triphenylarsine, triphenylstibine, and triphenylbismuthine, rare earth metal ions, and thenoyltrifluoroacetone

Rare earth metal ions containing polymer ternary complexes were synthesized and characterized. The functional polymers investigated were polymer-bond triphenylphosphine (PBDP), polymer-bond triphenylarsine (PBDAs), polymer-bond triphenylstibine (PBDSb), and polymer-bond triphenylbismuthine (PBDBi) as polymer ligands. Several substances, such as thenoyltrifluoroacetone (TTA), and 8-hydroxyquinoline (oxin), phenanthroline (phen) were used as low molecular weight ligands. The results show that TTA is the best low molecular weight ligand among them. The fluorescence properties of synthesized complexes were investigated; PBDAs is a better polymer ternary complex that possesses stronger fluorescence intensity coordinated with any low molecular weight ligand. The fluorescence lifetimes of Eu3+-containing polymer ternary complexes are between 0.350 and 0.469 MS. The reaction conditions of the formation and stability of rare earth metal ions–polymer–TTA ternary complexes are discussed.

Preparation and PH Responsive Behavior of Poly(Vinyl Alcohol)— Chitosan—Poly(Acrylic acid) Full-IPN Hydrogels

A full-interpenetrating polymer network (Full-IPN) hydrogel based on poly(vinyl alcohol)/chitosan/poly(acrylic acid) by the simultaneous-IPN method was synthesized and characterized by FT-IR and scanning electron microscopy. By varying the composition, different gels with different swelling dynamics, pH behavior and shrinking behavior of the gels were obtained. All the hydrogels swelled and reached equilibrium within five hours, indicating that the hydrogels have fast swelling properties and a relatively high swelling ratio (SR). Increasing the hydrophilic PAA in the full-IPN hydrogels increased the SR. The introduction of PVA and CTS to the full-IPN enhanced the hydrogels biocompatibility. The poly(vinyl alcohol)/chitosan/poly(acrylic acid) full-IPN hydrogels exhibited a swelling change in response to pH of the swelling medium, and could be useful a potential modulation systems in biomedical fields.

Graft copolymerization of artemisia seed gum with acrylic acid under microwave and its water absorbency

A super‐absorbent polymer was prepared by grafting copolymerization of acrylic acid onto Artemisia seed gum, using microwave irradiation and ammonium persulfate as an initiator. The effect of various preparation conditions on its water absorbency, such as the ratio of acrylic acid to Artemisia seed gum, degree of acrylic acid neutralization, amount of initiator and microwave irradiation time, was investigated by orthogonal tests. The optimal reaction conditions were 3 min (irradiation time), 70% neutralization degree of acrylic acid and 2% initiator on the basis of the mass of acrylic acid used. When the mass ratio of acrylic acid to Artemisia seed gum is 5:0.5, the product has a water absorbency close to 400 times at room temperature in distilled water, this indicated that is has a high water absorbency. The structure of the graft copolymer was confirmed by Fourier transform infrared spectrometer (FT‐IR) and thermogravimetric analysis (TGA). Further more, this microwave irradiation processing method to prepare water absorbent materials has no industrial cast off produced, that is to say, this method is environmentally friendly.

Preparation and catalysis of porous silica supported metal Schiff-base complex

A series of porous silica support metal Schiff-base complexes was synthesized with amino porous silica, salicylaldehyde and metal ion, which characterized by IR spectra, elemental analysis, and SEM. The catalytic property for oxidation of olefins in the presence of molecular oxygen has been investigated. The major product of the aerobic oxidation without reductant was the epoxy. The influence of reaction temperature and additive for epoxidation had been studied. The selectivity and the conversion of epoxidation varied with reaction time, different additives and different catalysts.

Synthesis and characterisation of seleno-Cynomorium songaricum Rupr. polysaccharide

In this article, the structural properties of Cynomorium songaricum Rupr. polysaccharide (CSP) after selenylation were investigated. The crude polysaccharide was obtained from C. songaricum Rupr. by water extraction followed by ethanol precipitation and freeze vacuum drying. Then selenylation of CSP has been accomplished by employing sodium selenite to modify the polysaccharide under the catalysis of nitric acid–barium chloride. After selenylation, the sugar content and the molecular weight increased but the protein content reduced. The maximum selenic content determined by ICP-AES was 2925 µg g−1. The selenide CSP (Se-CSP) was characterised by the methods of UV spectra, FT-IR, Raman spectra and X-ray photoelectron spectroscopy. The results showed that the hydroxyl hydrogen of the sugar moieties was substituted by Se=O. Thermal stability of Se-CSP was also measured by TG-DTA.

Oxidation of Styrene with Molecular Oxygen Catalyzed by Polymer‐Supported O‐Aminobenzoic Acid Salicylaldehyde Schiff‐Base Copper(II) Complex

Schiff‐base complexes of copper supported on chloromethylated polystyrene as a catalyst have been studied in the oxidation of styrene with molecular oxygen. The main products are benzaldehyde and the epoxide of styrene. Compared with the unsupported copper complex, the polymer supported complex has more effective catalytic activity, and could be easily separated and reused. The influences of reaction temperature and the amount of catalyst have also been investigated.

Preparation and catalytic oxidation by polymer supported 4-(2-pyridylazo) rosorcinol–metal complexes

Abstract Polymer-supported 4-(2-pyridylazo) rosorcinol–metal complexes (PS-PAR-M, M=Cu, Co, Ni, Fe) were prepared and characterized by IR, ICP, XPS, and used in the oxidation of ethylbenzene as catalyst. In comparison with their catalytic activities, PS-PAR-Cu was a more effective catalyst for the oxidation of ethylbenzene without solvent. The influences of reaction temperature, the amount of catalyst and substrate concentration, as well as reaction time on the oxidation of ethylbenzene have been investigated. The reaction optimum conditions have been obtained.

Polymer-bound schiff-base complex catalyst for effective oxidation of olefins with molecular oxygen

Polymer-bound Schiff-base ligand (PS–SalPhe) was prepared from polystyrene-bound salicylaldehyde and phenylalanine, and its complex (PS–SalPhe–M) (M = Co, Mn) was also synthesized. The polymer ligand and its complex were characterized by infrared spectra, small area X-ray photoelectron spectroscopy, and ICP–AES. In the presence of the complex, cyclohexene can be effectively oxidized by molecular oxygen without a reductant. The major products of the reaction are 2-cyclohexen-1-ol (—OH), 2-cyclohexen-1-one (CO), and 2-cyclohexen-1-hydroperoxide (—OOH ), which is different from the typical oxidation of cyclohexene. The mechanism of cyclohexene oxidation is also discussed. Long-chain linear aliphatic olefins, such as 1-octene, 1-decene, 1-dodecene, and 1-tetradecene, can be directly oxidized by molecular oxygen catalyzed by PS–SalPhe–M (M = Mn, Co), which yields the 1,2-epoxy alkane.