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2016 Volume 79 Issue 12
2016, 79(12): 1106-1112
Abstract:
Ionic liquids (ILs) have excellent solubility and stability, structure tunability and negligible vapor pressures, which make them be suitable reaction media for organic synthesis and catalyst. However, the large-scale application of ILs is still far from realization because of their high cost and difficult recovery. Superparamagnetic nanoparticles can be simply and efficiently removed from reaction mixtures with an external magnetic field. However, they are sensitive to agglomeration and can't be stably dispersed in the reaction system due to their high specific surface energy and magnetic dipole interactions. Using organic or inorganic substance to coat magnetic nanoparticles can form a kind of core-shell structure composite materials, which not only prevent them from agglomerating but also in favour of surface functionalization. Therefore, the immobilization of ILs on the surface of core-shell structure magnetic nanoparticles and the preparation of recyclable heterogeneous catalysts has been widely concerned. In this paper, the preparation method of core-shell magnetic nanoparticles supported IL catalysts as well as their applications in organic synthesis are reviewed, and the direction of the further research is suggested.
Ionic liquids (ILs) have excellent solubility and stability, structure tunability and negligible vapor pressures, which make them be suitable reaction media for organic synthesis and catalyst. However, the large-scale application of ILs is still far from realization because of their high cost and difficult recovery. Superparamagnetic nanoparticles can be simply and efficiently removed from reaction mixtures with an external magnetic field. However, they are sensitive to agglomeration and can't be stably dispersed in the reaction system due to their high specific surface energy and magnetic dipole interactions. Using organic or inorganic substance to coat magnetic nanoparticles can form a kind of core-shell structure composite materials, which not only prevent them from agglomerating but also in favour of surface functionalization. Therefore, the immobilization of ILs on the surface of core-shell structure magnetic nanoparticles and the preparation of recyclable heterogeneous catalysts has been widely concerned. In this paper, the preparation method of core-shell magnetic nanoparticles supported IL catalysts as well as their applications in organic synthesis are reviewed, and the direction of the further research is suggested.
2016, 79(12): 1113-1120
Abstract:
Polymer-supported catalysts with core-shell structure have attracted great attention in the area of catalytic chemistry because of the unique structure, morphology and properties of the supporting materials. This article reviews the preparation and corresponding catalytic performance of the catalysts of polymer supported metal nanoparticles with core-shell structure, which comprise spherical polymer brushes supported metal nanoparticles, polymer hollow microspheres loaded with metal nanoparticles, polymer solid microspheres coating with metal nanoparticles. The influence of the composition and the structure characteristics of support materials on the catalytic activity and stability of the catalysts are illustrated. Finally the advantages and short-comings of such catalytic materials are summarized, in addition, the prospect of performance and applications are also forecasted.
Polymer-supported catalysts with core-shell structure have attracted great attention in the area of catalytic chemistry because of the unique structure, morphology and properties of the supporting materials. This article reviews the preparation and corresponding catalytic performance of the catalysts of polymer supported metal nanoparticles with core-shell structure, which comprise spherical polymer brushes supported metal nanoparticles, polymer hollow microspheres loaded with metal nanoparticles, polymer solid microspheres coating with metal nanoparticles. The influence of the composition and the structure characteristics of support materials on the catalytic activity and stability of the catalysts are illustrated. Finally the advantages and short-comings of such catalytic materials are summarized, in addition, the prospect of performance and applications are also forecasted.
2016, 79(12): 1121-1126,1112
Abstract:
2,3,5,6-tetra(2-pyridyl) pyrazine (tppz) is one of the most fascinating molecules in terpyridine analogues. Investigation of tppz complexes is very important because of their potential applications in many areas such as molecular electronics, biochemistry, magnetics, catalysis and molecular sensors. The research advances of tppz complexes on the field of application in the past decade are reviewed.
2,3,5,6-tetra(2-pyridyl) pyrazine (tppz) is one of the most fascinating molecules in terpyridine analogues. Investigation of tppz complexes is very important because of their potential applications in many areas such as molecular electronics, biochemistry, magnetics, catalysis and molecular sensors. The research advances of tppz complexes on the field of application in the past decade are reviewed.
2016, 79(12): 1127-1133
Abstract:
The detection of biomolecules in the fields of clinical diagnosis, gene therapy and mutation analysis has become increasingly important. Therefore, it is significant for establishing a simple, rapid and sensitive detection method. Electrochemical biosensor has gained increasing interest because of its advantages such as simplicity, portability, easy to operate and low cost in the field of biomolecules detection. In order to improve the sensitivity of biosensors, different isothermal nucleic acid amplification techniques have been used in the construction of electrochemical biosensors. In this paper, we introduced the principle of electrochemical sensor briefly, summarize the main isothermal nucleic acid amplification techniques applied in electrochemical biosensors emphatically and compare the advantages and disadvantages of each technique.
The detection of biomolecules in the fields of clinical diagnosis, gene therapy and mutation analysis has become increasingly important. Therefore, it is significant for establishing a simple, rapid and sensitive detection method. Electrochemical biosensor has gained increasing interest because of its advantages such as simplicity, portability, easy to operate and low cost in the field of biomolecules detection. In order to improve the sensitivity of biosensors, different isothermal nucleic acid amplification techniques have been used in the construction of electrochemical biosensors. In this paper, we introduced the principle of electrochemical sensor briefly, summarize the main isothermal nucleic acid amplification techniques applied in electrochemical biosensors emphatically and compare the advantages and disadvantages of each technique.
2016, 79(12): 1134-1138,1133
Abstract:
Astringent compounds are one of the predominant factors to the quality of foods and beverages. Research on astringency perception has attracted great interest over past decades due to its positive effects on the human body including antibacterial, anticarcinogenic, antioxidant, and neuroprotective effects. Astringency is described as a ‘drying, roughing, puckering and astringent sensation’ in the mouth following consumption of astringent compounds such as polyphenols. It is debated whether astringency is a taste sensation or tactile sensation, or a trigeminal sensation analogous to spicy taste. Studies on the mechanisms of astringency are based on protein precipitation theory. This paper gives a brief introduction of the astringent compounds and mechanisms of astringency perception.
Astringent compounds are one of the predominant factors to the quality of foods and beverages. Research on astringency perception has attracted great interest over past decades due to its positive effects on the human body including antibacterial, anticarcinogenic, antioxidant, and neuroprotective effects. Astringency is described as a ‘drying, roughing, puckering and astringent sensation’ in the mouth following consumption of astringent compounds such as polyphenols. It is debated whether astringency is a taste sensation or tactile sensation, or a trigeminal sensation analogous to spicy taste. Studies on the mechanisms of astringency are based on protein precipitation theory. This paper gives a brief introduction of the astringent compounds and mechanisms of astringency perception.
2016, 79(12): 1139-1144
Abstract:
The effects of MoO3 loading content, impregnation temperature and calcination temperature on the performance of MoS2/Al2O3 sulfur-resistant catalysts for methanation reaction were studied. XRD and H2-TPR were employed to investigate the phases and reduction property of catalysts. Results showed that with the increasing of MoO3 content, the interaction between MoO3 and Al2O3 enhances and the content of Al2(MoO4)3 increases, which result in the increase of reduction temperature. Catalyst impregnated at 70℃ has higher CO conversion and CH4 selectivity and lower CO2 selectivity. The MoO3 content increases, and the reduction temperature decreases. With the increasing of calcination temperature, CO conversion increases firstly and then decreases, but has little effects on CH4 and CO2 selectivity. Catalyst calcinated at 450℃ has the highest CO conversion, while the catalyst calcinated at 600℃ has the lowest CO conversion rate. The peaks of Al2(MoO4)3 and Mo4O11 nearly disappear at calcinated temperature of 400℃ to 450℃, and well crystallized MoO3 are formed. Therefore, the best calcination temperature range is 400~450℃.
The effects of MoO3 loading content, impregnation temperature and calcination temperature on the performance of MoS2/Al2O3 sulfur-resistant catalysts for methanation reaction were studied. XRD and H2-TPR were employed to investigate the phases and reduction property of catalysts. Results showed that with the increasing of MoO3 content, the interaction between MoO3 and Al2O3 enhances and the content of Al2(MoO4)3 increases, which result in the increase of reduction temperature. Catalyst impregnated at 70℃ has higher CO conversion and CH4 selectivity and lower CO2 selectivity. The MoO3 content increases, and the reduction temperature decreases. With the increasing of calcination temperature, CO conversion increases firstly and then decreases, but has little effects on CH4 and CO2 selectivity. Catalyst calcinated at 450℃ has the highest CO conversion, while the catalyst calcinated at 600℃ has the lowest CO conversion rate. The peaks of Al2(MoO4)3 and Mo4O11 nearly disappear at calcinated temperature of 400℃ to 450℃, and well crystallized MoO3 are formed. Therefore, the best calcination temperature range is 400~450℃.
2016, 79(12): 1145-1149
Abstract:
Cordierite loaded Fe-Mo catalyst was prepared by impregnation method. The structure and morphology of the catalyst were characterized by SEM, FT-IR, XRD, EDX and XPS methods. It was found that the catalyst calcined at 450℃ under argon atmosphere has superior performance in the catalytic synthesis of ethylene. In addition, effects of the reaction temperature, air velocity and H2/CO molar ratio on catalytic performance were also discussed. Under the reaction conditions of H2/CO=2, WHSV=2.0 L/g cat·h, and 450℃, the selectivity of ethylene and carbon monoxide conversion rate were 46.3% and 63.5%, respectively. The Fe-Mo-cat has high ethylene efficiency for syngas conversion, and this study may provide a new reference for industrial production of ethylene.
Cordierite loaded Fe-Mo catalyst was prepared by impregnation method. The structure and morphology of the catalyst were characterized by SEM, FT-IR, XRD, EDX and XPS methods. It was found that the catalyst calcined at 450℃ under argon atmosphere has superior performance in the catalytic synthesis of ethylene. In addition, effects of the reaction temperature, air velocity and H2/CO molar ratio on catalytic performance were also discussed. Under the reaction conditions of H2/CO=2, WHSV=2.0 L/g cat·h, and 450℃, the selectivity of ethylene and carbon monoxide conversion rate were 46.3% and 63.5%, respectively. The Fe-Mo-cat has high ethylene efficiency for syngas conversion, and this study may provide a new reference for industrial production of ethylene.
2016, 79(12): 1150-1155
Abstract:
Considering a variety of biological activities of bisindolyl maleimide and thiourea compounds, seventeen 3,4-bis(indole-3-yl)-2,5-diketone-1-pyrrole imine thiourea compounds were synthesized through the reaction of 1-amino-3,4-di(indole-3-yl)-3-pyrroline-2,5-diketone with isothiocyanate. Their structures were confirmed by 1H NMR, 13C NMR and HRMS (ESI). The preliminary antitumor activities tests of the prepared compounds were performed. The results showed that most of the compounds have good inhibitory activity (above 96%) against cell division cycle 25B (CDC 25B), so they may have potential application in antitumor drug discovery.
Considering a variety of biological activities of bisindolyl maleimide and thiourea compounds, seventeen 3,4-bis(indole-3-yl)-2,5-diketone-1-pyrrole imine thiourea compounds were synthesized through the reaction of 1-amino-3,4-di(indole-3-yl)-3-pyrroline-2,5-diketone with isothiocyanate. Their structures were confirmed by 1H NMR, 13C NMR and HRMS (ESI). The preliminary antitumor activities tests of the prepared compounds were performed. The results showed that most of the compounds have good inhibitory activity (above 96%) against cell division cycle 25B (CDC 25B), so they may have potential application in antitumor drug discovery.
2016, 79(12): 1156-1160
Abstract:
2-Amino-4H-pyran derivatives were synthesized under the catalysis of zinc acetate using cyano chalcones and malononitrile as raw materials. Influences of catalysts, solvents, reaction time and temperature, mole ratio of raw material on the yield were studied. The optimal conditions are as follows, molar ratio of cyano chalcones and malononitrile is 1:1, zinc acetate (10(mol)%) as catalyst, methylene chloride as solvent, the reaction temperature is 30℃. Under this condition, the highest yield of target product can reach 99.5%.
2-Amino-4H-pyran derivatives were synthesized under the catalysis of zinc acetate using cyano chalcones and malononitrile as raw materials. Influences of catalysts, solvents, reaction time and temperature, mole ratio of raw material on the yield were studied. The optimal conditions are as follows, molar ratio of cyano chalcones and malononitrile is 1:1, zinc acetate (10(mol)%) as catalyst, methylene chloride as solvent, the reaction temperature is 30℃. Under this condition, the highest yield of target product can reach 99.5%.
2016, 79(12): 1161-1165
Abstract:
A reactive water-soluble UV-absorber, (4-((4-chloro-6-(((2R,3R,4R,5S)-2-(2,2-dimethyl-1,3-dioxolan-4-yl) -4,5-dihydroxytetrahydrofuran-3-yl)oxy)-1,3,5-triazin-2-yl)oxy)-2-hydroxyphenyl)(phenyl) methanone (UV-DTM), was synthesized by using 2,4-dihydroxy benzophenone (UV-0), diacetone glucose and 2,4,6-trichloro-1,3,5-triazine (TCT) as the main raw materials. The structure was confirmed by IR, NMR and MS. The highest yield (73%) of DTDT can be obtained in the conditions:n (TCT):n (diacetone glucose):n (NaOH)=0.9:1:1.7 and 0℃, 8 h. The highest yield (74%) of UV-DT can be obtained in the conditions:n (DTDT):n (UV-0):n(NaOH)=1:1.1:1 and 30℃, 2 h. The highest yield (74%) of UV-DTM can be obtained in the conditions:0.5 mL hydrochloric acid (36%) with each millimole of UV-DT, 25℃, 5 h. The UV-absorption of UV-DTM in 240~400 nm was strong, and its water solubility was improved.
A reactive water-soluble UV-absorber, (4-((4-chloro-6-(((2R,3R,4R,5S)-2-(2,2-dimethyl-1,3-dioxolan-4-yl) -4,5-dihydroxytetrahydrofuran-3-yl)oxy)-1,3,5-triazin-2-yl)oxy)-2-hydroxyphenyl)(phenyl) methanone (UV-DTM), was synthesized by using 2,4-dihydroxy benzophenone (UV-0), diacetone glucose and 2,4,6-trichloro-1,3,5-triazine (TCT) as the main raw materials. The structure was confirmed by IR, NMR and MS. The highest yield (73%) of DTDT can be obtained in the conditions:n (TCT):n (diacetone glucose):n (NaOH)=0.9:1:1.7 and 0℃, 8 h. The highest yield (74%) of UV-DT can be obtained in the conditions:n (DTDT):n (UV-0):n(NaOH)=1:1.1:1 and 30℃, 2 h. The highest yield (74%) of UV-DTM can be obtained in the conditions:0.5 mL hydrochloric acid (36%) with each millimole of UV-DT, 25℃, 5 h. The UV-absorption of UV-DTM in 240~400 nm was strong, and its water solubility was improved.
2016, 79(12): 1166-1172
Abstract:
Simultaneous determination of dissociation constants of three monoprotic weak base drugs, propranolol, atenolol and metoprolol were achieved through internal standard capillary electrophoresis. Three compounds that have similar properties and dissociation constants with the analytes, ephedrine, procaine and diphenhydramine were selected as the internal standards. Precise dissociation constants of the internal standards were deduced using iterative calculation by internal standard capillary electrophoresis. Effective electrophoretic mobilities of the internal standards and the analytes have been determined under the conditions that they are partly or totally protonated. Dissociation constants of the three analytes were further determined simultaneously through single internal standard and multi-internal standards systems, the precision and accuracy of the method were investigated. The relative standard deviation of experimental results were in the range of 0.26%~0.96%, and the obtained values were accurate within 0.1 pKa uint compared with results of monocomponent determination under the same conditions and the literature values. The technology did not require accurate pH measurement of the buffer solution. Only two electrophoretic runs are needed to complete simultaneous determination of dissociation constants of the three drugs, so the consumed experiment time is shortened significantly. Therefore the proposed method is highly appropriate for high throughput evaluation and screening of drugs in drug development process.
Simultaneous determination of dissociation constants of three monoprotic weak base drugs, propranolol, atenolol and metoprolol were achieved through internal standard capillary electrophoresis. Three compounds that have similar properties and dissociation constants with the analytes, ephedrine, procaine and diphenhydramine were selected as the internal standards. Precise dissociation constants of the internal standards were deduced using iterative calculation by internal standard capillary electrophoresis. Effective electrophoretic mobilities of the internal standards and the analytes have been determined under the conditions that they are partly or totally protonated. Dissociation constants of the three analytes were further determined simultaneously through single internal standard and multi-internal standards systems, the precision and accuracy of the method were investigated. The relative standard deviation of experimental results were in the range of 0.26%~0.96%, and the obtained values were accurate within 0.1 pKa uint compared with results of monocomponent determination under the same conditions and the literature values. The technology did not require accurate pH measurement of the buffer solution. Only two electrophoretic runs are needed to complete simultaneous determination of dissociation constants of the three drugs, so the consumed experiment time is shortened significantly. Therefore the proposed method is highly appropriate for high throughput evaluation and screening of drugs in drug development process.
2016, 79(12): 1173-1177
Abstract:
In aqueous solution, fluorescence resonance energy transfer (FRET) behavior may occur between quantum dots (QDs) and organic fluorescent dyes. The FRET system was constructed by using the CdS QDs with an emission wavelength of 470 nm as an energy donor and Eosin Y as an acceptor. Some parameters of the FRET system were studied. In this system, the ratio of acceptor/donor was 8, quenching efficiency was 45.6%, reinforcing efficiency was 20.1%, distance between donor and acceptor was 4.4 nm, critical energy transfer distance was 2.4 nm.
In aqueous solution, fluorescence resonance energy transfer (FRET) behavior may occur between quantum dots (QDs) and organic fluorescent dyes. The FRET system was constructed by using the CdS QDs with an emission wavelength of 470 nm as an energy donor and Eosin Y as an acceptor. Some parameters of the FRET system were studied. In this system, the ratio of acceptor/donor was 8, quenching efficiency was 45.6%, reinforcing efficiency was 20.1%, distance between donor and acceptor was 4.4 nm, critical energy transfer distance was 2.4 nm.
2016, 79(12): 1178-1183
Abstract:
Organo-montmorillonites 12-2-12-MMT and 16-2-16-MMT were prepared by two modification treatment of cationic Gemini surfactants 1,2-bis(dodecyldimethylammonio)ethanedibromide(12-2-12) and 1,2-bis(cetyldimethylammonio) ethanedibromide (16-2-16). The modified samples were characterized by XRD, FT-IR and TG-DTG, and the results showed that the surfactants had inserted into the lamella of montmorillonite successfully, the interlayer spacer increased with the increasing of the cationic exchange capacity (CEC) of surfactants and the chain length. The adsorption experiments of methyl orange onto organo-montmorillonite were studied using batch method as a function of the concentration of surfactants, contact time, temperature and pH. The optimal conditions for methyl orange adsorption were 1.0 CEC of MMT, 20℃, pH 3, and contact time 6 h. The adsorption capability of 16-2-16-MMT was better than that of 12-2-12-MMT. The kinetic data were better described by the pseudo-second order kinetics model. The adsorption isotherm was in good agreement with the Langmuir model.
Organo-montmorillonites 12-2-12-MMT and 16-2-16-MMT were prepared by two modification treatment of cationic Gemini surfactants 1,2-bis(dodecyldimethylammonio)ethanedibromide(12-2-12) and 1,2-bis(cetyldimethylammonio) ethanedibromide (16-2-16). The modified samples were characterized by XRD, FT-IR and TG-DTG, and the results showed that the surfactants had inserted into the lamella of montmorillonite successfully, the interlayer spacer increased with the increasing of the cationic exchange capacity (CEC) of surfactants and the chain length. The adsorption experiments of methyl orange onto organo-montmorillonite were studied using batch method as a function of the concentration of surfactants, contact time, temperature and pH. The optimal conditions for methyl orange adsorption were 1.0 CEC of MMT, 20℃, pH 3, and contact time 6 h. The adsorption capability of 16-2-16-MMT was better than that of 12-2-12-MMT. The kinetic data were better described by the pseudo-second order kinetics model. The adsorption isotherm was in good agreement with the Langmuir model.
2016, 79(12): 1184-1188
Abstract:
The stability and isomerization mechanisms of HO(S)CC(S)OH have been investigated by the CBS-QB3 composite approach. Eleven isomers and twelve transition states were obtained and the possible reaction pathways were probed. The results indicated that the order of stability is M11 > M7 > M10 > M1 > M9 > M6 > M2 > M3=M4>M5. The activation free energy associated with the C-C bond rotation paths are all small, and they are easily converted into the O-H bond rotation isomers. In addition, the isomerization of M6 to M11 is most favorable both thermodynamically and kinetically in all isomerizations, which should be the dominant process.
The stability and isomerization mechanisms of HO(S)CC(S)OH have been investigated by the CBS-QB3 composite approach. Eleven isomers and twelve transition states were obtained and the possible reaction pathways were probed. The results indicated that the order of stability is M11 > M7 > M10 > M1 > M9 > M6 > M2 > M3=M4>M5. The activation free energy associated with the C-C bond rotation paths are all small, and they are easily converted into the O-H bond rotation isomers. In addition, the isomerization of M6 to M11 is most favorable both thermodynamically and kinetically in all isomerizations, which should be the dominant process.
2016, 79(12): 1189-1191
Abstract:
(4R)-2-Phenylthiazolidine-4-carboxylic acid (2) was prepared from L-cysteine and benzaldehyde. Esterification of compound 2 produced (4R)-methyl-2-phenylthiazolidine-4-carboxylate (3). Then hydantoin (1) was obtained through the reaction of compound 3 with triphosgene and benzylamine. The total yield of the three steps is approximately 87%. The structures of compounds 1~3 were characterized by 1H NMR, 13C NMR, IR and MS. This method is environmentally friendly, lower cost, and suitable for industrial production.
(4R)-2-Phenylthiazolidine-4-carboxylic acid (2) was prepared from L-cysteine and benzaldehyde. Esterification of compound 2 produced (4R)-methyl-2-phenylthiazolidine-4-carboxylate (3). Then hydantoin (1) was obtained through the reaction of compound 3 with triphosgene and benzylamine. The total yield of the three steps is approximately 87%. The structures of compounds 1~3 were characterized by 1H NMR, 13C NMR, IR and MS. This method is environmentally friendly, lower cost, and suitable for industrial production.
2016, 79(12): 1192-1195
Abstract:
A facile, green approach to diuron is reported. Using cheap, well-available nonmetal selenium as catalyst, CO instead of virulent phosgene as the carbonylation reagent, the target product can be obtained directly by one-pot selenium-catalyzed redox carbonylation of 3,4-dichloronitrobenzene with dimethylamine hydrochloride. The optimal reaction conditions were obtained through experimental researches on reaction time, temperature, kinds of solvents and bases, CO pressure and mole ratio of dimethylamine hydrochloride to 3,4-dichloronitrobenzene etc. Under the optimal reaction conditions, the target product can be obtained in 70% yield. Thus, a brief, simple, low-cost, high atom economic, and environmentally friendly approach to diuron is developed. A plausible route to diuron was presented at the end of this paper.
A facile, green approach to diuron is reported. Using cheap, well-available nonmetal selenium as catalyst, CO instead of virulent phosgene as the carbonylation reagent, the target product can be obtained directly by one-pot selenium-catalyzed redox carbonylation of 3,4-dichloronitrobenzene with dimethylamine hydrochloride. The optimal reaction conditions were obtained through experimental researches on reaction time, temperature, kinds of solvents and bases, CO pressure and mole ratio of dimethylamine hydrochloride to 3,4-dichloronitrobenzene etc. Under the optimal reaction conditions, the target product can be obtained in 70% yield. Thus, a brief, simple, low-cost, high atom economic, and environmentally friendly approach to diuron is developed. A plausible route to diuron was presented at the end of this paper.
2016, 79(12): 1196-1199
Abstract:
The structure of (IrO2)n(n=1~5) nanoclusters are completed optimized by using the UB3LYP density function theory. Energy, vibration frequency, electronic properties and stability have been calculated. The optimized geometries clear that (IrO2)n nanoclusters are of planar (n=1, 2) and three-dimensional (n>2) configurations. The calculated results showed that there are more charge transfer between the bridge site oxygen and iridium atoms. Moreover, the dissociation energy showed that Ir4O8 possess relatively high stabilities of the (IrO2)n(n=2~5) nanoclusters. However, magic number of n=2, 4 for the nanoclusters were obtained by the investigations on vertical ionization potential and vertical electron affinity.
The structure of (IrO2)n(n=1~5) nanoclusters are completed optimized by using the UB3LYP density function theory. Energy, vibration frequency, electronic properties and stability have been calculated. The optimized geometries clear that (IrO2)n nanoclusters are of planar (n=1, 2) and three-dimensional (n>2) configurations. The calculated results showed that there are more charge transfer between the bridge site oxygen and iridium atoms. Moreover, the dissociation energy showed that Ir4O8 possess relatively high stabilities of the (IrO2)n(n=2~5) nanoclusters. However, magic number of n=2, 4 for the nanoclusters were obtained by the investigations on vertical ionization potential and vertical electron affinity.
2016, 79(12): 1200-1203
Abstract:
Erich Armand Arthur Joseph Hückel (1896-1980) was a German physical chemist. Hückel have been called one of the most important pioneers of quantum chemistry. He is known for two major contributions:(a) the Debye-Hückel theory of electrolytic solutions, (b) the Hückel method of approximate molecular orbital (MO) calculations on π-electron systems. This paper reviews his life and achievements, especially his contributions to physical chemistry.
Erich Armand Arthur Joseph Hückel (1896-1980) was a German physical chemist. Hückel have been called one of the most important pioneers of quantum chemistry. He is known for two major contributions:(a) the Debye-Hückel theory of electrolytic solutions, (b) the Hückel method of approximate molecular orbital (MO) calculations on π-electron systems. This paper reviews his life and achievements, especially his contributions to physical chemistry.
2016, 79(12): 1204-1208
Abstract:
The influential factors for the rate of reactions occurring in solution which is different from those occurring in gaseous phase are discussed. The perception that the presence of solvent molecules will cause a significant decrease in the collision frequency between reactant molecules is proved incorrect. Except for the changes in activity of reactants and the catalysis due to the presence of solvent, solvent effect and micro-viscosity are found to be the two main factors affecting the rate of the solution reactions. The micro-viscosity is either of positive value due to the interaction between reactants and solvent molecules or of negative value due to the small molar mass of solvent which moves with higher speed. Based on the simple collision theory and transition state theory, a general kinetic equation correlating the change in reaction rate to the change in activation energy and micro-viscosity is proposed. Base on this equation, more satisfactory explanations to the experimental facts can be given.
The influential factors for the rate of reactions occurring in solution which is different from those occurring in gaseous phase are discussed. The perception that the presence of solvent molecules will cause a significant decrease in the collision frequency between reactant molecules is proved incorrect. Except for the changes in activity of reactants and the catalysis due to the presence of solvent, solvent effect and micro-viscosity are found to be the two main factors affecting the rate of the solution reactions. The micro-viscosity is either of positive value due to the interaction between reactants and solvent molecules or of negative value due to the small molar mass of solvent which moves with higher speed. Based on the simple collision theory and transition state theory, a general kinetic equation correlating the change in reaction rate to the change in activation energy and micro-viscosity is proposed. Base on this equation, more satisfactory explanations to the experimental facts can be given.
