SO_4^(2-)/TiO_(2)-WO_(3)was prepared and its catalytic activity under differentsynthetic conditions was discussed with esterification of n-butanoic acid and n-butyl alcohol asprobing reaction.The optimum conditions ar...SO_4^(2-)/TiO_(2)-WO_(3)was prepared and its catalytic activity under differentsynthetic conditions was discussed with esterification of n-butanoic acid and n-butyl alcohol asprobing reaction.The optimum conditions are found that the mass fraction of H_2WO_4 used in thecompound is 12.5 percent,the calcination temperature is 580 deg C,the calcination time is 3 h,andthe soaked consistency of H_2SO_4 is 1.0 mol centre dot L^(-1).Then SO_4^(2-)/TiO_(2)-WO_(3)wasapplied as the catalyst in the catalytic synthesis of eight similar important ketals and acetalsunder the optimum conditions and revealed high catalytic activity.On condition that the molar ratioof aldehyde/ketone to glycol is 1:1.5,the mass fraction of the catalyst used in the reactants is0.5 percent,and the reaction time is 1.0 h,the yields of ketals and acetals can reach 64.2percent-95.1 percent.Moreover,it can be easily recovered and reused.展开更多
The double perovskite oxides Sr2Mg1-xF exMoO6-δ were investigated as catalysts for the methane oxidation.The structural properties of catalysts were characterized in detail by X-ray diffraction,X-ray photoelectron sp...The double perovskite oxides Sr2Mg1-xF exMoO6-δ were investigated as catalysts for the methane oxidation.The structural properties of catalysts were characterized in detail by X-ray diffraction,X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.The catalytic property was strongly influenced by the Fe substitution.The relation between catalytic performance and the degree of Fe substitution was examined with regard to the structure and surface characteristics of the mixed oxides.The Fe-containing catalysts exhibited higher activity attributable to the possible（Fe2＋,Mo6＋） and （Fe3＋,Mo5＋）valency pairs,and the highest activity was observed for Sr2Mg0.2Fe0.8MoO6-δ.The enhancement of the catalytic activity may be correlated with the Fe-relating surface lattice oxygen species and was discussed in view of the presence of oxygen vacancies.展开更多
Since the relationship between angiogenesis and tumor growth was established by Folkman in 1971, scientists have made efforts exploring the possibilities in treating cancer by targeting angiogenesis. Inhibition of ang...Since the relationship between angiogenesis and tumor growth was established by Folkman in 1971, scientists have made efforts exploring the possibilities in treating cancer by targeting angiogenesis. Inhibition of angiogenesis growth factors and administration of angiogenesis inhibitors are the basics of anti- angiogenesis therapy. Transfer of anti-angiogenesis genes has received attention recently not only because of the advancement of recombinant vectors, but also because of the localized and sustained expression of therapeutic gene product inside the tumor after gene transfer. This review provides the up-to-date information about the strategies and the vectors studied in the field of anti-angiogenesis cancer gene therapy.展开更多
catalyst for the synthesis of 14-aryl- 14-H-dibenzo[aj]xanthenes Silica supported ammonium dihydrogen phosphate （NH4H2PO4/SiO2） is found to be a recyclable heterogeneous catalyst for a rapid and efficient synthesis ...catalyst for the synthesis of 14-aryl- 14-H-dibenzo[aj]xanthenes Silica supported ammonium dihydrogen phosphate （NH4H2PO4/SiO2） is found to be a recyclable heterogeneous catalyst for a rapid and efficient synthesis of various aryl-14-H-dibenzo[a,j]xanthenes with excellent yields under solvent-free conditions. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times and milder conditions. 2009 Shahnaz Rostamizadeh. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
Six new thermally stable polyesters （4a-f） were synthesized through the solution polycondensation reaction of 2,5-pyridine dicarbonyldichloride （2） with six aromatic diols in N,N＇-dimethyl acetamide （DMAc） solu...Six new thermally stable polyesters （4a-f） were synthesized through the solution polycondensation reaction of 2,5-pyridine dicarbonyldichloride （2） with six aromatic diols in N,N＇-dimethyl acetamide （DMAc） solution and in the presence of pyridine as a base. The polycondensation reactions produce a series of new polyesters （4a-f） in high yields, and inherent viscosity between 0.30 and 0.55 dL/g. The resulting polyesters were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis （TGA and DTG）, solubility test, Fourier transform infrared （FT-IR） spectroscopy and gel permeation chromatography （GPC）. C 2009 Khalil Faghihi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
An efficient synthesis of thiazines from the three component reactions between dialkyl acetylenedicarboxylates, arylisothio- cyanates and N-nucleophiles at room temperature in water as the solvent is described.
The sorption behavior and mechanism of a novel chelate resin, diglycolamidic acid resin (DAAR), for Sm(III) were investigated. The optimal sorption condition of DAAR for Sm(III) is pH=6.0 in HAc-NaAc medium. The stati...The sorption behavior and mechanism of a novel chelate resin, diglycolamidic acid resin (DAAR), for Sm(III) were investigated. The optimal sorption condition of DAAR for Sm(III) is pH=6.0 in HAc-NaAc medium. The statically saturated sorption capacity is 190mg/g resin at 298K. The Sm(III) adsorbed on DAAR can be eluted reaching 100% by 0.5~2.0mol/L HCl used as eluant. The resin can be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant is k298= 1.96×10-5s-1. The apparent activation energy is 26kJ/mol. The sorption behavior of DAAR for Sm(III) obeys the Freundlich isotherm. The thermodynamic sorption parameters, enthalpy change 腍 of DAAR for Sm(III) is 16.9kJ/mol. The molar coordination ratio of the functional group of DAAR to Sm (III) is 3. The sorption mechanism of DAAR for Sm(III) was examined by using chemical method and IR spectrometry. The coordination bond was formed between oxygen atoms in the functional group of DAAR and Sm(III).展开更多
Two hydrogen-bonding adsorbents-macroporous crosslinked poly(p-nitrostyrene) and poly(p-vinylbenzyl amide)--were synthesized, and the absorption property of phenol from cyclohexane solution onto the adsorbents was stu...Two hydrogen-bonding adsorbents-macroporous crosslinked poly(p-nitrostyrene) and poly(p-vinylbenzyl amide)--were synthesized, and the absorption property of phenol from cyclohexane solution onto the adsorbents was studied. The differential adsorption heats for varied adsorption capacities calculated from the adsorption isotherms according to the Clapeyron-Clausius equation lay in the range of hydrogen bond energy (8-50kJ/mol). The adsorption capacity of o-nitrophenol in cyclohexane was much less than that of phenol under the same condition. The adsorption capacity of phenol from cyclohexane onto polyacrylonitile was much less than that onto poly(p-nitrostyrene) or poly(p-vinylbenzyl amide). All these results revealed that adsorption of phenol from cyclohexane by poly(p-nitrostyrene) or poly(p-vinylbenzyl amide) is based on hydrogen-bonding.展开更多
The luminescent nanosized Eu-MCM （1：10） was synthesized by means of sol-gel-assisted self-assembly under basic conditions at room temperature. The results of ^29Si-MAS NMR show that the peaks are Q^4, Q^3, Q^2[ （...The luminescent nanosized Eu-MCM （1：10） was synthesized by means of sol-gel-assisted self-assembly under basic conditions at room temperature. The results of ^29Si-MAS NMR show that the peaks are Q^4, Q^3, Q^2[ （SiO）4-mSi - （OH）m（m=0, 1, 2）, at -δ111, -δ103, -δ90], and q^3, q^2, q^1, q^0[（SiO）4-nSi-（O-Eu）n（n=1, 2, 3, 4）, at - δ83, - δ72, - δ55, - δ47]. The result proves Eu^3＋ doped Si - O framework. The HRTEM image shows that the regular uniform nanoparticles with a diameter of 15 nm possess large pore with Ф8 nm, which is consistent with the result of N2 adsorption. The patterns of selected-area electron diffraction, XRD, and pore-size distribution plot of Eu-MCM （ 1 ： 10） show that the sample of Eu-MCM （ 1 ： 10） possesses the both of crystal and amorphous phases. The FT IR results indicate that the peaks near 970 cm^-1 are assigned to the deformation vibration of silanol group. The as-product was calcined at 800 ℃ and the mesoporous material possesses enormous specific areas and large pores, which shows that the mesoporous material is ultrastable.展开更多
The overall reaction was determined on the basis of the dissociation constant of TBA and the ratio of the ligand to the rare earth ion in the complex.The rate law,rate constants and acitivition energies for the reacti...The overall reaction was determined on the basis of the dissociation constant of TBA and the ratio of the ligand to the rare earth ion in the complex.The rate law,rate constants and acitivition energies for the reaction of La^(3+),Gd^(3+)and Ho^(3+)with TBA were studied.It is shown in the study that prerequisites for performing differential rate analysis for binary rare earths with TBA are that the pseudo-first-order parallel reaction mechanism should be conformed with,no multinuclear complex would be formed and the co-coloration effects could be neglected.展开更多
A novel ternary solid complex, Yb （C5H8NS2）3 （C12H8N2）, was obtained from treating hydrous ytterbium chloride, ammonium pyrrolidin- edithiocarbamate （ APDC ） and 1, 10-phenanthroline （o-phen· H2O） in abso...A novel ternary solid complex, Yb （C5H8NS2）3 （C12H8N2）, was obtained from treating hydrous ytterbium chloride, ammonium pyrrolidin- edithiocarbamate （ APDC ） and 1, 10-phenanthroline （o-phen· H2O） in absolute ethanol, and characterized by elemental analysis. The enthalpies of solution of hydrous ytterbium chloride, APDC, o-phen·H2O, the mixture of APDC with o-phen· H2O in absolute ethanol at 298. 15 K, and the enthalpy changes of liquid- phase reaction of formation for Yb （ C5H8NS2 ）3 （ C12H8N2） at different temperatures were measured by using a RD496-Ⅲ microcalorimeter. Fundamental paconduction microcalorimeter, determining the specific heat a calculation model for capacity of solid subrameters, the activation enthalpy （ΔH≠^θ）, the activation entropy （ΔS≠^θ）, the activation free energy （ΔG≠^θ）, the apparent reaction rate constant （k）, the apparent activation energy （ E ）, the pre-exponential constant （A） and the reaction order （n）, were obtained by the combination of the thermochemical data of the reaction and kinetic equations with the data of thermokinetic experiments. The enthalpy change of complex formation from the reaction of the regents in solid phase, ΔrH≠^θ（s）, was calculated on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. Based on a RD496-Ⅲ heat stance was developed, and the title complex, c m, were accordingly determined.展开更多
A novel morphine alkaloid, named gindarudine 1 has been isolated from ethanol extract of Stephania glabra tubers, together with four known alkaloids, palmatine, dehydrocorydalmine, stepharanine, and 8-（4＇-methoxyben...A novel morphine alkaloid, named gindarudine 1 has been isolated from ethanol extract of Stephania glabra tubers, together with four known alkaloids, palmatine, dehydrocorydalmine, stepharanine, and 8-（4＇-methoxybenzyl）-xylopinine. Compound 1 was elucidated as 3,6-O,N-detrimethyl-10-hydroxy-l-methoxy-thebaine by means of spectroscopic data including 2D NMR studies. C 2009 Deepak Kumar Semwal. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
Li0.24＋2xLa0.59-xMxTiO3-LaPO4（M = K, Na） fast ionic conductor was synthesized by high temperature solid state reaction. A.C. Impedance measurements show that the compositions of system have better conductivities in...Li0.24＋2xLa0.59-xMxTiO3-LaPO4（M = K, Na） fast ionic conductor was synthesized by high temperature solid state reaction. A.C. Impedance measurements show that the compositions of system have better conductivities in low doping content of Na^＋ and K^＋ , as the doping content increases, the conductivity goes down in Na^＋ doping system. But in doping K^＋ system, the conductivity goes down and then goes up with the increasing content of K^＋. The activation energies of different doped ions are about 20 kJ·mol^-1 in the temperature range of 25 - 400℃. X-ray powder diffraction shows that the doped Na^＋ and K^＋ would not affect the structure of compositions in the system. The main phase is Li0.24＋2xLa0.59-x MxTiO3 perovskite solid solution, LaPO4 as a second phase also can be found. With increasing the content of M （x 〉 0.04）, unknown phase appears. IR measurement also indicates that the structure of compositions in the system would not be affected by doping alkali ion.展开更多
Rare earth complex Tb（BA）3phen was synthesized, which is first used as an emitting material in electroluminescence. The properties of monolayer device with the swing film rote of 1000 r·min^-1（70 nm） and the ...Rare earth complex Tb（BA）3phen was synthesized, which is first used as an emitting material in electroluminescence. The properties of monolayer device with the swing film rote of 1000 r·min^-1（70 nm） and the weight ratio of 1：5 （PVK：Tb（BA）3phen） are the best. And the highest brightness of this device reached 26.8 cd·cm^-2 at a fixed bias of 21 V. Bright green emission could be obtained from the optimized double-layer device and the highest EL brightness of the device reached 322 cd·m^-2 at the voltage of 22 V.展开更多
Eleven new rare earth complexes with aliphatic Schiff base, condensed from diglycol aldehyde and bis-arginine, were synthesized and characterized. They are confirmed as Ln （H2DAAR） （NO3）3·7H2O （ Ln = La, Pr,...Eleven new rare earth complexes with aliphatic Schiff base, condensed from diglycol aldehyde and bis-arginine, were synthesized and characterized. They are confirmed as Ln （H2DAAR） （NO3）3·7H2O （ Ln = La, Pr, Nd, Gd）, Ln3 （H2DAAR）2（NO3）9·5H2O （Ln= Dy, Y）and Ln2（H2DAAR）（NO3）6·3H2O （Ln = La, Nd, Sm, Gd）, Ln3（DAAR） （NO3）7·4H2O （Ln = Dy, Yb, Y） respectively under different molar ratios of metal to ligand （DAAR = diglycol aldehyde bis-arginine）. The present paper deals with a synthetic method and catalytic properties of obtained complexes. The result shows that proper pH value is important for synthesis of the complexes and compositions of the lighter and the heavier rare earth complexes are different under the same reaction condition. Some new complexes obtained have proved their catalytic activity and 80% conversion with the viscosity-average molecular weight 230,000 for the polymerization of methyl methacrylate （MMA） without addition of any cocatalyst.展开更多
Possibilities for enhancement of catalytic reaction rate by combining phase transfer catalysis and hydrogen bonding of the catalyst with the substrate and reagent were studied. A phase transfer catalyst library with s...Possibilities for enhancement of catalytic reaction rate by combining phase transfer catalysis and hydrogen bonding of the catalyst with the substrate and reagent were studied. A phase transfer catalyst library with sixty polystyrene-supported quaternary ammonium salt catalysts was synthesized. The reduction of acetophenone by NaBH, was used as the probing reaction to select out the most active catalyst in the library by using iterative method, which was the gel-type triethanolamine aminating strongly basic anion exchange resin with the crosslinking degree of 2% A hydrogen bonding assisted catalytic mechanism was proposed to explain the high catalytic activity of the catalyst.展开更多
Formic acid is available as a major byproduct from biorefinery processing and this together with its unique properties,including non-toxicity,favorable energy density,and biodegradability,make it an economically appea...Formic acid is available as a major byproduct from biorefinery processing and this together with its unique properties,including non-toxicity,favorable energy density,and biodegradability,make it an economically appealing and safe reagent for energy storage and chemical synthesis.This review provides an overview of novel recent achievements in green catalytic transformations that use biogenic formic acid as an efficient and versatile reagent.The examples selected demonstrate the advantages of formic acid in addressing the key issues(minimizing the use and generation of hazardous substances while maximizing productivity under mild and benign reaction conditions)in clean chemical transformation.Special emphasis is put on the prospects of formic acid for delivering new catalytic technology to produce a plethora of tailor-made products via the flexible and selective conversion of renewable biomass resources.The potential of formic acid as a renewable C1 feedstock for both bulk and fine chemical syntheses is also outlined with examples.The role of multifunctionality in catalyst design as a key aspect in developing new catalytic concepts capable of promoting new transformations to give unprecedented selectivity and efficiency is also discussed.This article is expected to advance research on sustainable,green and affordable bio-based processes as alternatives to traditional ones with the goal to develop a fully sustainable chemical industry based on renewable resources.展开更多
To address problems such as aging,mutation,and cancer,it is of great importance to understand the damage mechanism of DNA induced by hydroxyl radical.In this study,the abstraction reaction mechanism of hydroxyl radica...To address problems such as aging,mutation,and cancer,it is of great importance to understand the damage mechanism of DNA induced by hydroxyl radical.In this study,the abstraction reaction mechanism of hydroxyl radical with guanine-cytosine(GC)base pair in aqueous phase under the polarized continuum model(PCM)has been explored by using density functional theory(DFT).The results indicated that all the abstraction reactions in GC base pair were thermodynamically exothermic,and the stability of dehydrogenation radicals decreased in the order of(H2b-GC)〉(GC-H4b)〉(GC-H6)〉(GC-H5)-(H8-GC).The reaction energy of H2b abstraction pathway was the lowest among all investigated pathways,thus indicating that the reaction conversion of(H2b-GC)was the highest.In the five hydrogen abstraction pathways,the local energy barriers with respect to the corresponding reactant complexes increased in the following order:H2b〈H4b〈H5〈H6〈H8,thereby suggesting that the H2b abstraction pathway was the most rapid.Thus,H2b abstraction process was the most likely favorable reaction pathway.Another compatible pathway would be the H4b abstraction,followed by H6 and H5 abstraction pathways in thermodynamics and in kinetics.H8 abstraction process was the least favorable pathway,as consistent with the formation of hydroxylation adduct observed experimentally rather than the hydrogen abstraction radical.展开更多
基金supported by the Natural Science Foundation of Hubei Province Education Committee(Nos.2004D007and2002A00008)the National Natural Science Foundation of China(No.20471044)
文摘SO_4^(2-)/TiO_(2)-WO_(3)was prepared and its catalytic activity under differentsynthetic conditions was discussed with esterification of n-butanoic acid and n-butyl alcohol asprobing reaction.The optimum conditions are found that the mass fraction of H_2WO_4 used in thecompound is 12.5 percent,the calcination temperature is 580 deg C,the calcination time is 3 h,andthe soaked consistency of H_2SO_4 is 1.0 mol centre dot L^(-1).Then SO_4^(2-)/TiO_(2)-WO_(3)wasapplied as the catalyst in the catalytic synthesis of eight similar important ketals and acetalsunder the optimum conditions and revealed high catalytic activity.On condition that the molar ratioof aldehyde/ketone to glycol is 1:1.5,the mass fraction of the catalyst used in the reactants is0.5 percent,and the reaction time is 1.0 h,the yields of ketals and acetals can reach 64.2percent-95.1 percent.Moreover,it can be easily recovered and reused.
基金the financial supports from the National Natural Science Foundation of China(No.20703042)National Basic Research Program of China(No.2010CB923300)+1 种基金USTC-NSRL Association Funding(No.KY2060030009)the Fundamental Research Funds for the Central Universities
文摘The double perovskite oxides Sr2Mg1-xF exMoO6-δ were investigated as catalysts for the methane oxidation.The structural properties of catalysts were characterized in detail by X-ray diffraction,X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.The catalytic property was strongly influenced by the Fe substitution.The relation between catalytic performance and the degree of Fe substitution was examined with regard to the structure and surface characteristics of the mixed oxides.The Fe-containing catalysts exhibited higher activity attributable to the possible（Fe2＋,Mo6＋） and （Fe3＋,Mo5＋）valency pairs,and the highest activity was observed for Sr2Mg0.2Fe0.8MoO6-δ.The enhancement of the catalytic activity may be correlated with the Fe-relating surface lattice oxygen species and was discussed in view of the presence of oxygen vacancies.
基金Supported by grant from the Innovation and Technology
文摘Since the relationship between angiogenesis and tumor growth was established by Folkman in 1971, scientists have made efforts exploring the possibilities in treating cancer by targeting angiogenesis. Inhibition of angiogenesis growth factors and administration of angiogenesis inhibitors are the basics of anti- angiogenesis therapy. Transfer of anti-angiogenesis genes has received attention recently not only because of the advancement of recombinant vectors, but also because of the localized and sustained expression of therapeutic gene product inside the tumor after gene transfer. This review provides the up-to-date information about the strategies and the vectors studied in the field of anti-angiogenesis cancer gene therapy.
文摘catalyst for the synthesis of 14-aryl- 14-H-dibenzo[aj]xanthenes Silica supported ammonium dihydrogen phosphate （NH4H2PO4/SiO2） is found to be a recyclable heterogeneous catalyst for a rapid and efficient synthesis of various aryl-14-H-dibenzo[a,j]xanthenes with excellent yields under solvent-free conditions. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times and milder conditions. 2009 Shahnaz Rostamizadeh. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
文摘Six new thermally stable polyesters （4a-f） were synthesized through the solution polycondensation reaction of 2,5-pyridine dicarbonyldichloride （2） with six aromatic diols in N,N＇-dimethyl acetamide （DMAc） solution and in the presence of pyridine as a base. The polycondensation reactions produce a series of new polyesters （4a-f） in high yields, and inherent viscosity between 0.30 and 0.55 dL/g. The resulting polyesters were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis （TGA and DTG）, solubility test, Fourier transform infrared （FT-IR） spectroscopy and gel permeation chromatography （GPC）. C 2009 Khalil Faghihi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
文摘An efficient synthesis of thiazines from the three component reactions between dialkyl acetylenedicarboxylates, arylisothio- cyanates and N-nucleophiles at room temperature in water as the solvent is described.
基金The Natural Science Foundation of Zhejiang Province (No.200072)
文摘The sorption behavior and mechanism of a novel chelate resin, diglycolamidic acid resin (DAAR), for Sm(III) were investigated. The optimal sorption condition of DAAR for Sm(III) is pH=6.0 in HAc-NaAc medium. The statically saturated sorption capacity is 190mg/g resin at 298K. The Sm(III) adsorbed on DAAR can be eluted reaching 100% by 0.5~2.0mol/L HCl used as eluant. The resin can be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant is k298= 1.96×10-5s-1. The apparent activation energy is 26kJ/mol. The sorption behavior of DAAR for Sm(III) obeys the Freundlich isotherm. The thermodynamic sorption parameters, enthalpy change 腍 of DAAR for Sm(III) is 16.9kJ/mol. The molar coordination ratio of the functional group of DAAR to Sm (III) is 3. The sorption mechanism of DAAR for Sm(III) was examined by using chemical method and IR spectrometry. The coordination bond was formed between oxygen atoms in the functional group of DAAR and Sm(III).
基金Supported by the National Natural Science Foundation of China !(Grant No. 29574164 and 29974015)
文摘Two hydrogen-bonding adsorbents-macroporous crosslinked poly(p-nitrostyrene) and poly(p-vinylbenzyl amide)--were synthesized, and the absorption property of phenol from cyclohexane solution onto the adsorbents was studied. The differential adsorption heats for varied adsorption capacities calculated from the adsorption isotherms according to the Clapeyron-Clausius equation lay in the range of hydrogen bond energy (8-50kJ/mol). The adsorption capacity of o-nitrophenol in cyclohexane was much less than that of phenol under the same condition. The adsorption capacity of phenol from cyclohexane onto polyacrylonitile was much less than that onto poly(p-nitrostyrene) or poly(p-vinylbenzyl amide). All these results revealed that adsorption of phenol from cyclohexane by poly(p-nitrostyrene) or poly(p-vinylbenzyl amide) is based on hydrogen-bonding.
基金Project supported by Appropriative Research Fund for Professor and Doctor , Guangdong Institute of Education (ARF0406)
文摘The luminescent nanosized Eu-MCM （1：10） was synthesized by means of sol-gel-assisted self-assembly under basic conditions at room temperature. The results of ^29Si-MAS NMR show that the peaks are Q^4, Q^3, Q^2[ （SiO）4-mSi - （OH）m（m=0, 1, 2）, at -δ111, -δ103, -δ90], and q^3, q^2, q^1, q^0[（SiO）4-nSi-（O-Eu）n（n=1, 2, 3, 4）, at - δ83, - δ72, - δ55, - δ47]. The result proves Eu^3＋ doped Si - O framework. The HRTEM image shows that the regular uniform nanoparticles with a diameter of 15 nm possess large pore with Ф8 nm, which is consistent with the result of N2 adsorption. The patterns of selected-area electron diffraction, XRD, and pore-size distribution plot of Eu-MCM （ 1 ： 10） show that the sample of Eu-MCM （ 1 ： 10） possesses the both of crystal and amorphous phases. The FT IR results indicate that the peaks near 970 cm^-1 are assigned to the deformation vibration of silanol group. The as-product was calcined at 800 ℃ and the mesoporous material possesses enormous specific areas and large pores, which shows that the mesoporous material is ultrastable.
基金The Project was supported by the National Natural Science Foundation of China
文摘The overall reaction was determined on the basis of the dissociation constant of TBA and the ratio of the ligand to the rare earth ion in the complex.The rate law,rate constants and acitivition energies for the reaction of La^(3+),Gd^(3+)and Ho^(3+)with TBA were studied.It is shown in the study that prerequisites for performing differential rate analysis for binary rare earths with TBA are that the pseudo-first-order parallel reaction mechanism should be conformed with,no multinuclear complex would be formed and the co-coloration effects could be neglected.
文摘A novel ternary solid complex, Yb （C5H8NS2）3 （C12H8N2）, was obtained from treating hydrous ytterbium chloride, ammonium pyrrolidin- edithiocarbamate （ APDC ） and 1, 10-phenanthroline （o-phen· H2O） in absolute ethanol, and characterized by elemental analysis. The enthalpies of solution of hydrous ytterbium chloride, APDC, o-phen·H2O, the mixture of APDC with o-phen· H2O in absolute ethanol at 298. 15 K, and the enthalpy changes of liquid- phase reaction of formation for Yb （ C5H8NS2 ）3 （ C12H8N2） at different temperatures were measured by using a RD496-Ⅲ microcalorimeter. Fundamental paconduction microcalorimeter, determining the specific heat a calculation model for capacity of solid subrameters, the activation enthalpy （ΔH≠^θ）, the activation entropy （ΔS≠^θ）, the activation free energy （ΔG≠^θ）, the apparent reaction rate constant （k）, the apparent activation energy （ E ）, the pre-exponential constant （A） and the reaction order （n）, were obtained by the combination of the thermochemical data of the reaction and kinetic equations with the data of thermokinetic experiments. The enthalpy change of complex formation from the reaction of the regents in solid phase, ΔrH≠^θ（s）, was calculated on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. Based on a RD496-Ⅲ heat stance was developed, and the title complex, c m, were accordingly determined.
文摘A novel morphine alkaloid, named gindarudine 1 has been isolated from ethanol extract of Stephania glabra tubers, together with four known alkaloids, palmatine, dehydrocorydalmine, stepharanine, and 8-（4＇-methoxybenzyl）-xylopinine. Compound 1 was elucidated as 3,6-O,N-detrimethyl-10-hydroxy-l-methoxy-thebaine by means of spectroscopic data including 2D NMR studies. C 2009 Deepak Kumar Semwal. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
基金Project supported bythe Science Technology Development Foundation of Fuzhou University (2002-XY-06)
文摘Li0.24＋2xLa0.59-xMxTiO3-LaPO4（M = K, Na） fast ionic conductor was synthesized by high temperature solid state reaction. A.C. Impedance measurements show that the compositions of system have better conductivities in low doping content of Na^＋ and K^＋ , as the doping content increases, the conductivity goes down in Na^＋ doping system. But in doping K^＋ system, the conductivity goes down and then goes up with the increasing content of K^＋. The activation energies of different doped ions are about 20 kJ·mol^-1 in the temperature range of 25 - 400℃. X-ray powder diffraction shows that the doped Na^＋ and K^＋ would not affect the structure of compositions in the system. The main phase is Li0.24＋2xLa0.59-x MxTiO3 perovskite solid solution, LaPO4 as a second phase also can be found. With increasing the content of M （x 〉 0.04）, unknown phase appears. IR measurement also indicates that the structure of compositions in the system would not be affected by doping alkali ion.
基金Project supported bythe National Natural Science Foundation of China (90201004) and Beijing Science &Technology Founda-tion
文摘Rare earth complex Tb（BA）3phen was synthesized, which is first used as an emitting material in electroluminescence. The properties of monolayer device with the swing film rote of 1000 r·min^-1（70 nm） and the weight ratio of 1：5 （PVK：Tb（BA）3phen） are the best. And the highest brightness of this device reached 26.8 cd·cm^-2 at a fixed bias of 21 V. Bright green emission could be obtained from the optimized double-layer device and the highest EL brightness of the device reached 322 cd·m^-2 at the voltage of 22 V.
基金Project supported by Natural Science Foundation of Zhejiang Province (202033)
文摘Eleven new rare earth complexes with aliphatic Schiff base, condensed from diglycol aldehyde and bis-arginine, were synthesized and characterized. They are confirmed as Ln （H2DAAR） （NO3）3·7H2O （ Ln = La, Pr, Nd, Gd）, Ln3 （H2DAAR）2（NO3）9·5H2O （Ln= Dy, Y）and Ln2（H2DAAR）（NO3）6·3H2O （Ln = La, Nd, Sm, Gd）, Ln3（DAAR） （NO3）7·4H2O （Ln = Dy, Yb, Y） respectively under different molar ratios of metal to ligand （DAAR = diglycol aldehyde bis-arginine）. The present paper deals with a synthetic method and catalytic properties of obtained complexes. The result shows that proper pH value is important for synthesis of the complexes and compositions of the lighter and the heavier rare earth complexes are different under the same reaction condition. Some new complexes obtained have proved their catalytic activity and 80% conversion with the viscosity-average molecular weight 230,000 for the polymerization of methyl methacrylate （MMA） without addition of any cocatalyst.
基金Supported by the National Natural Science Foundation of China !(Grant No. 29574164 and 29974015)
文摘Possibilities for enhancement of catalytic reaction rate by combining phase transfer catalysis and hydrogen bonding of the catalyst with the substrate and reagent were studied. A phase transfer catalyst library with sixty polystyrene-supported quaternary ammonium salt catalysts was synthesized. The reduction of acetophenone by NaBH, was used as the probing reaction to select out the most active catalyst in the library by using iterative method, which was the gel-type triethanolamine aminating strongly basic anion exchange resin with the crosslinking degree of 2% A hydrogen bonding assisted catalytic mechanism was proposed to explain the high catalytic activity of the catalyst.
文摘Formic acid is available as a major byproduct from biorefinery processing and this together with its unique properties,including non-toxicity,favorable energy density,and biodegradability,make it an economically appealing and safe reagent for energy storage and chemical synthesis.This review provides an overview of novel recent achievements in green catalytic transformations that use biogenic formic acid as an efficient and versatile reagent.The examples selected demonstrate the advantages of formic acid in addressing the key issues(minimizing the use and generation of hazardous substances while maximizing productivity under mild and benign reaction conditions)in clean chemical transformation.Special emphasis is put on the prospects of formic acid for delivering new catalytic technology to produce a plethora of tailor-made products via the flexible and selective conversion of renewable biomass resources.The potential of formic acid as a renewable C1 feedstock for both bulk and fine chemical syntheses is also outlined with examples.The role of multifunctionality in catalyst design as a key aspect in developing new catalytic concepts capable of promoting new transformations to give unprecedented selectivity and efficiency is also discussed.This article is expected to advance research on sustainable,green and affordable bio-based processes as alternatives to traditional ones with the goal to develop a fully sustainable chemical industry based on renewable resources.
文摘To address problems such as aging,mutation,and cancer,it is of great importance to understand the damage mechanism of DNA induced by hydroxyl radical.In this study,the abstraction reaction mechanism of hydroxyl radical with guanine-cytosine(GC)base pair in aqueous phase under the polarized continuum model(PCM)has been explored by using density functional theory(DFT).The results indicated that all the abstraction reactions in GC base pair were thermodynamically exothermic,and the stability of dehydrogenation radicals decreased in the order of(H2b-GC)〉(GC-H4b)〉(GC-H6)〉(GC-H5)-(H8-GC).The reaction energy of H2b abstraction pathway was the lowest among all investigated pathways,thus indicating that the reaction conversion of(H2b-GC)was the highest.In the five hydrogen abstraction pathways,the local energy barriers with respect to the corresponding reactant complexes increased in the following order:H2b〈H4b〈H5〈H6〈H8,thereby suggesting that the H2b abstraction pathway was the most rapid.Thus,H2b abstraction process was the most likely favorable reaction pathway.Another compatible pathway would be the H4b abstraction,followed by H6 and H5 abstraction pathways in thermodynamics and in kinetics.H8 abstraction process was the least favorable pathway,as consistent with the formation of hydroxylation adduct observed experimentally rather than the hydrogen abstraction radical.
