分子印迹聚合物负载Fe(III)催化剂的底物识别性能

分别以o-, m-和p-硝基苯甲醇与FeCl₃的配合物为模板分子,丙烯酰胺为功能单体,二甲基丙烯酸乙二醇酯为交联剂,采用本体聚合法制备了三种Fe(III)含量相同的分子印迹聚合物(MIP)o-Fe(III)-MIP,m-Fe(III)-MIP和p-Fe(III)-MIP.并采用扫描电镜、N₂吸附-脱附及红外光谱等方法对催化剂结构进行了表征.在以水为溶剂,过氧化氢(30%)为氧化剂的苯甲醇衍生物氧化反应中,该类催化剂表现出优异的催化活性和独特的底物识别性能.当以p-Fe(III)-MIP为催化剂时,p-硝基苯甲醇的转化率达到80%,而在其他两个催化剂上均低于58%.这表明Fe(III)-MIP催化剂结构中具有与底物分子匹配的印迹空腔与识别位点,对底物分子表现出专一识别性,因而提高了催化剂对底物的选择性.     

Reactivity of methyl (3,6-dichloropyridazin-4-yl)acetate towards nucleophiles

Methyl (3,6-dichloropyridazin-4-yl)acetate (II), prepared from methyl (3,6-dihydroxypyrid-azin-4-yl)aeetate (1) by chlurination with phosphorus oxychloride, was used for studies of nucleo-philic displacement reactions and it has been found that only the chlorine atom at position 6 was displaced with hydrazine. With diluted hydrochloric acid both chlorine atoms were displaced with the 6-oxo isomer predominating. By turning the aromatic ring of pyridazine into an o-quinoid system, the chlorine atom at position 3 became mobile. Cyelization of (6-hydrazino-s-triazolo-[4,3-b ]pyridazin-7-yl)acetic acid hydrazide (XIX) gave 6-aminopyrrolo[3,2-e ]s-triazlo[ 4,3-b ]-pyridazm-7(8H)one (XXI).     

Tuning the thermochromism of water-soluble poly(3-thiopheneacetic acid) conjugated polymer by complexation with zwitterionic polymer

The spectral properties and phase behavior of the complexes of the water-soluble poly(3-thiopheneacetic acid) (P3TAA) conjugated polymer with zwitterionic 3-dimethyl(methacryloyloxyethyl) ammonium propane sulfone (PDMAPS) polymer were explored. A dramatic change in both electronic spectra and upper critical solution temperature (UCST) of P3TAA-PDMAPS complex solution was observed depending on the molar ratio of P3TAA and PDMAPS, suggesting that a conformational transition due to complexation occurred. The UV–vis λ_max of P3TAA-PDMAPS complex solutions was changed dramatically in a narrow temperature range around a UCST and found to be varied over approximately a 40 nm range by the temperature change of about 20 °C.     

Synthesis of novel nitrogen-containing polymers by Pd(0)-catalyzed polycondensation of propargylic carbonates and bifunctional nitrogen nucleophiles

A Pd(0)-catalyzed polycondensation of propargylic carbonates and bifunctional nitrogen nucleophiles was investigated. The polycondensation was carried out in THF at 80 °C for 20 h in the presence of a Pd(0) catalyst. The Pd(0)-catalyzed polycondensation with bifunctional nitrogen nucleophiles proceeded successfully when bis[(2-diphenylphosphino)phenyl]ether (DPEphos) was used as the ligand. N-monoalkylated bifunctional benzenesulfonamides and pyromellitic diimide could be used in the polycondensation. Aliphatic and aromatic amines did not afford the corresponding polymers at all. The molecular weights of the obtained polymers were higher when propargylic carbonates having an aryl group on the acetylenic terminal carbon were used.     

Heterogeneous hydrogenation catalyses over recyclable Pd(0) nanoparticle catalysts stabilized by PAMAM-SBA-15 organic-inorganic hybrid composites

Pd(0) nanoparticle catalysts stabilized by Gn-PAMAM-SBA-15 (n = 1-4) organic-inorganic hybrid composites were successfully prepared. Heterogeneous hydrogenation reaction of allyl alcohol over the Pd(0)-Gn-PAMAM-SBA-15 catalysts showed their high activities with TOFs of 2185, 2266, 711, and 739 and selectivities of 79.0, 82.0, 93.4, and 91.4%, respectively. The activity over the Pd(0)-G4-PAMAM-SBA-15 catalyst was 1.5 times that over the fourth generation PAMAM encapsulated Pd(0) homogeneous catalyst. These catalysts can be easily recovered, reused multiple times, and preserved for one month in the air, maintaining high catalytic efficiencies.     

Studies on the thermotropic liquid-crystalline polymer. IX. Synthesis and properties of crosslinkable copoly(amide-ester)s containing conjugated double bonds

Four series of copoly(amide-ester)s containing conjugated double bonds were prepared by using direct polycondensation in the presence of diphenylchlorophosphate (DPCP) and pyridine. Series I–III were prepared from para, meta-aminophenol, or their mixture with p-phenylene bis(acrylic acid) (PPBA), p-carboxylic cinnamic acid (PCCA), and stilbenedicarboxylic acid (SDBA), respectively. Series IV was prepared from a mixture of aminophenols [2-methyl 4-aminophenol (MePAP) and m-aminophenol (MAP)] with a mixture of diacids (PPBA and SDBA). Thermotropic liquid-crystalline behavior of these polymers was studied by differential scanning calorimetry (DSC), and optical polarizing microscopy equipped with a heating stage. Series I , series II , and P40–P100 of series IV could undergo crosslinking reaction by heating. However, series III could undergo crosslinking reaction only by photoirradiation upon heating. After crosslinking reaction occurred, the properties of these polymers were also examined by DSC, TGA, WAXD, and IR. The synthesized polymers could be crosslinked in the liquid-crystalline phase with retention of the order in the final crosslinked solid. © 1993 John Wiley & Sons, Inc.     

Cyclization of azines with bifunctional nucleophiles — a one-step route to condensed heterocycles (review)

Nucleophilic diaddition and disubstitution in the azine. series with the participation of bifunctional reagents, the result of which is the formation of condensed heterocycles, were examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1026, August, 1985.     

多羟乙基双核大环多胺La(III)配合物对双对硝基苯酚磷酸二酯和DNA 催化水解作用研究

合成了一类新型多羟乙基双核大环多胺La(III)配合物, 其结构经1H NMR, MS, 元素分析等表征. 通过紫外分光光谱法和琼脂糖凝胶电泳技术, 研究了双核大环多胺La(III)配合物催化双对硝基苯酚磷酸二酯的水解反应和对质粒DNA(pUC18)的催化水解作用. 结果表明: 双核大环多胺La(III)配合物可以有效催化双对硝基苯酚磷酸二酯水解和促进质粒DNA在生理条件下的水解裂解. 双对硝基苯酚磷酸二酯的水解速率提高了2.36×104倍. 讨论了配合物结构对水解反应的影响.     

Hydrolysis of p-nitrophenyl picolinate catalyzed by metal complexes of N-alkyl-3,5-bis(hydroxymethyl)-1,2,4-triazole in CTAB micelles

Two lipophilic ligands containing triazole and hydroxyl groups, N-alkyl(C(n)H(2n+1))-3,5-bis(hydroxymethyl)-1,2,4-triazole (n=10 and 12), were synthesized. Effects of their Cu(II) and Ni(II) complexes on the hydrolysis of p-nitrophenyl picolinate (PNPP) in cetyltrimethylammonium bromide (CTAB) micelles have been investigated kinetically, and some kinetic parameters of the reactions were obtained by employing the ternary complex kinetic model for metallomicellar catalysis. It was found that Cu(II) complexes of these triazole-based ligands showed more effective catalytic activity on the hydrolysis of PNPP than Ni(II) complexes. Also, the apparent first-order rate constants for product formation in the metallomicellar phase (k(N)(')), the association constants between the substrate and the binary complex (K(T)), and the association constants between the metal ion and the ligand (K(M)) increased with an increase in pH value, which may be attributed to an increase in the nucleophilicity of the hydroxyl groups in the ligand or the electrophilicity of the substrate at higher pH. In addition, at constant pH, k(N)(') and K(T) increased with an increase in the hydrocarbon chain length of the ligand, while K(M) decreased.     

Degradation of polymer mixtures. VIII. Blends of poly(vinyl acetate) with poly(methyl methacrylate)

The degradation of blends of PVA and PMMA in the form of films cast from a common solution of the polymers has been studied by TVA, TG, and EGA (evolved gas analysis) for acetic acid. Volatile degradation products have been characterized by spectroscopic and GLC techniques. Molecular weight, spectral and thermal stability changes in PMMA extracted from partially degraded blends have been examined. These blends behave in a closely analogous manner to PVC-PMMA blends already investigated. The results suggest that the PMMA component of the heterogeneous blends is modified in two ways: (1) in a destabilization reaction series initiated by attack of acetate radicals generated in the PVA phase which migrate into the PMMA phase, and (2) in a stabilization reaction involving conversion of ester side groups to acid and subsequently to anhydride ring structures which act as blocking points for depolymerization. The rate of acetic acid production in the blend is less than in PVA degraded alone. The mechanism of degradation of PVA is reconsidered in the light of these results.     

Study on surface hydrolytic kinetics of poly(vinyl acetate) grafted onto polyurethane film

Alkali catalytic hydrolysis of poly(vinyl acetate) (PVAc) grafting onto polyurethane film surface was a heterogeneous reaction. The hydrolysis was carried on the PVAc particle surface, and the concentration of the alkali in the system was tested by titration method. The kinetics of PVAc surface hydrolytic reaction was studied by simple second-order reaction model. From linear regression analysis of experimental data, we inferred that the activation energy (E _a ) and pre-exponential factor (A) of PVAc surface hydrolytic reaction were 70.7 ± 0.2 kJ mol^?1 and (5.7 ± 0.5) × 10¹² kg mol^?1 s^?1, respectively. The results of transmission electron microscopy stated that the apparent hydrolytic degree was 2.1% when the surface of PVAc particle hydrolyzed absolutely.     

Degradation of polymer mixtures. VII. Blends of poly(vinyl acetate) with polystyrene

The degradation of films containing both PVA and PS has been investigated for comparison with the behavior already reported for PVC/PS blends. The presence of PS had little, if any, effect on the behavior of PVA, but PVA had an effect similar to that of PVC on the degradation of PS. Styrene production was retarded in the blend, compared to PS alone, and an increase in the rate of chain scission was observed for a high molecular weight sample. The molecular weight effect, however, was much smaller than in corresponding experiments with PVC/PS blends. Interference with intermolecular transfer in PS is again advanced as the probable explanation of the stabilization of PS.     

Heterocycles containing a bridge nitrogen atom. 11. Recyclization of 5-methyloxazolo[3,2-apyridinium cation under the action of nucleophiles containing NH2 group. Crystal structure of 3-(p-nitrophenyl)-1,4-dihydropyrido-[2,1-c]-as-triazinium perchlorate

Reactions of 5-methyl-2-(p-nitrophenyl)oxazolo[3,2-a]pyridinium perchlorate with ammonia and hydrazine, in contrast to the reaction with secondary amines, do not produce indolizines. The reaction with ammonia produces 5-methyl-2-(p-nitrophenyl)imidazo[1,2-a]pyridine; with hydrazine, 3-(p-nitrophenyl)-1,4-dihydropyrido[2,1-c]-as-triazinium semiperchlorate (2 moles of base per one mole of acid). The structure of the latter is solved by X-ray structural studies. Dedicated to Professor Henk van der Plas on his 70th birthday. For No. 9, see [1]. M. V. Lomonosov Moscow State University, Moscow 119899, Russia Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 550–556, April, 1999.     

Thermal studies of some biologically active oxovanadium(IV) complexes containing 8-hydroxyquinolinate and hydroxamate ligands

The thermal decomposition behaviours of oxovanadium(IV)hydroxamate complexes of composition [VO(Q)_2?n(HL^1,2)_n]: [VO(C₉H₆ON)(C₆H₄(OH)(CO)NHO)] (I), [VO(C₆H₄(OH)(CO)NHO)₂] (II), [VO(C₉H₆ON)(C₆H₄(OH)(5-Cl)(CO)NHO)] (III), and [VO(C₆H₄(OH)(5-Cl)(CO)NHO)₂] (IV) (where Q?=?C₉H₆NO^? 8-hydroxyquinolinate ion; HL¹?=?[C₆H₄(OH)CONHO]^? salicylhydroxamate ion; HL²?=?[C₆H₃(OH)(5-Cl)CONHO]^? 5-chlorosalicylhydroxamate ion; n?=?1 and 2), which are synthesised by the reactions of [VO(Q)₂] with predetermined molar ratios of potassium salicylhydroxamate and potassium 5-chlorosalicylhydroxamate in THF?+?MeOH solvent medium, have been studied by TG and DTA techniques. Thermograms indicate that complexes (I) and (III) undergo single-step decomposition, while complexes (II) and (IV) decompose in two steps to yield VO(HL^1,2) as the likely intermediate and VO₂ as the ultimate product of decomposition. The formation of VO₂ has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stabilities for the complexes has been inferred as III?>?I > II?>?IV.     

Enhanced cooperativity through design: pendant Co(III)--salen polymer brush catalysts for the hydrolytic kinetic resolution of epichlorohydrin (salen=N,N'-bis(salicylidene)ethylenediamine dianion)

The Co(III)--salen-catalyzed (salen=N,N'-bis(salicylidene)ethylenediamine dianion) hydrolytic kinetic resolution (HKR) of racemic epoxides has emerged as a highly attractive and efficient method of synthesizing chiral C(3) building blocks for intermediates in larger, more complex molecules. HKR reaction rates have displayed a second order dependency on the concentration of active sites, and thus researchers have proposed a bimetallic transition state for the HKR mechanism. Here we report the utilization of pendant Co(III)--salen catalysts on silica supported polymer brushes as a catalyst for the HKR of epichlorohydrin. The novel polymer brush architecture provided a unique framework for promoting site-site interactions as required in the proposed bimetallic transition state of the HKR mechanism. Furthermore, the polymer brushes mimic the environment of soluble polymer-based catalysts, whereas the silica support permitted facile recovery and reuse of the catalyst. The polymer brush catalyst displayed increased activities over the soluble Jacobsen Co--salen catalyst and was observed to retain its high enantioselectivities (>99 %) after each of five reactions despite decreasing activities. Analysis indicated decomposition of the salen ligand as an underlying cause of catalyst deactivation.