Two Mn(II)coordination supramolecules,[Mn2(C8H7O2)4(phen)2(μ-H2O)](1)and [Mn2(btec)(phen)2(H2O)6].2H2O(2)(phen=1,10-phenanthroline,H4btec=1,2,4,5-benzenetetracarboxylic acid),were synthesized by hydrothermal method.T...Two Mn(II)coordination supramolecules,[Mn2(C8H7O2)4(phen)2(μ-H2O)](1)and [Mn2(btec)(phen)2(H2O)6].2H2O(2)(phen=1,10-phenanthroline,H4btec=1,2,4,5-benzenetetracarboxylic acid),were synthesized by hydrothermal method.The crystal structures of the complexes were determined by X-ray single crystal diffraction.The result indicates that(1)and(2)are both binuclear Mn(II)complexes.The existence of hydrogen bonds makes the binuclear complexes become further connected to coordination su-pramolecules,which possess 1D and 3D infinite structures respectively.The complexes were identified by IR,UV-Vis,surface photovoltage spectrum(SPS)and field-induced surface photovoltage spectrum(FISPS).The results of SPS for the complexes indicate that they both exhibit positive surface photo-voltage response bands in the range of 300―600 nm.The SPS phase spectrum and FISPS of com-plexes indicate that they show certain p-type semiconductor characteristic.However,the intensity,position and number of the SPV response bands are different obviously.The difference of the SPV re-sponse bands is mainly attributed to the different structures of the complexes and the different coor-dination environment of Mn(Ⅱ)in the two complexes.This paper discusses the action of hydrogen bonds in the construction of the supramolecule and the change on the surface photovoltage of com-plex in different coordination environment.展开更多
The interaction by hydrogen bond formation of some primary alcohols （ l-heptanol, l-octanol and l-decanol） with esters （methyl methacrylate, ethyl methacrylate and butyl methacrylate） was investigated in non-polar...The interaction by hydrogen bond formation of some primary alcohols （ l-heptanol, l-octanol and l-decanol） with esters （methyl methacrylate, ethyl methacrylate and butyl methacrylate） was investigated in non-polar solvents viz., n-heptane, CC14 and benzene by means of FTIR spectroscopy. Formation constants and free energy changes of complex formation were determined. The dependence of the equilibrium constants and free energy changes of complex formation on the alkyl chain length of both the alcohols and esters are discussed. The solvent interaction between the solute and solvent. effect on the hydrogen bond formation is discussed in terms of specific展开更多
Changes of surface shape, aggregate state, and microstructure of Apocynum fiber before and after irradia-tion were studied by XRD, IR, SEM, ESR, and solid state 13C CP/ MAS NMR. The results show that the surface shape...Changes of surface shape, aggregate state, and microstructure of Apocynum fiber before and after irradia-tion were studied by XRD, IR, SEM, ESR, and solid state 13C CP/ MAS NMR. The results show that the surface shape and microstructure were not spoiled under 50 kGy gamma irradiation, while the crystallization of Apocynum fiber changed under 280 kGy . It also shows that different free radicals appear after irradiation and their concentration increases with the increase of irradiation dose.展开更多
With high association constants in nonpolar solvents, the quadruple hydrogen bonding arrays of 2-ureido-4[1H]-pyrimidinones are recently considered to be one of the ideal building blocks to construct the complicated a...With high association constants in nonpolar solvents, the quadruple hydrogen bonding arrays of 2-ureido-4[1H]-pyrimidinones are recently considered to be one of the ideal building blocks to construct the complicated and functional supramole- cular systems. In this paper, we review the latest achievements of the supramolecular assemblies based on 2-ureido-4[1H]-pyrimidinone AADD quad- ruple hydrogen bonding building blocks.展开更多
The adsorption and dissociation of CH3OH on TiO2 （110） were studied using density functional theory methods. Our results suggest that CH3OH molecules can adsorb up to 3/4 ML （1 ML=5.2× 10^14 molecules/cm2） co...The adsorption and dissociation of CH3OH on TiO2 （110） were studied using density functional theory methods. Our results suggest that CH3OH molecules can adsorb up to 3/4 ML （1 ML=5.2× 10^14 molecules/cm2） coverage at five-coordinated titanium （Tisc） sites to form the first layer. In the second layer, the CH3OH is adsorbed at bridge-bonded oxygen, and from the third layer, the CH3OH molecules form a hydrogen-bonded network with each other. The theoretical results show that dissociation of multilayer adsorbed methanol to aldehyde occurs through a stepwise pathway, with easy O-H bond dissociation and rate-determining C-H bond dissociation. The dissociation barriers for 8 or 12 CH3OH molecules on TiO2 are higher than that for low coverage by 0.15-0.21 eV; this suggests that the dissociation of multilayer adsorbed CH3OH is harder.展开更多
Dipeptides are stereo-specifically involved in several biological functions that are challenging to separate enantiomerically. Elution order of enantiomers is an important issue in chiral chromatography. Amylose tris-...Dipeptides are stereo-specifically involved in several biological functions that are challenging to separate enantiomerically. Elution order of enantiomers is an important issue in chiral chromatography. Amylose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase(CSP) is the best and most-widely-used CSP in chiral separations, but experimental data of enantiomeric separation of dipeptides on this CSP is lacking. Simulation studies were conducted to determine the order of elution and the chiral recognition mechanism of didpetides on this CSP. Results indicated that the docking energy of SR-enantiomers were higher than SS-antipodes. The range of docking energies for SR-enantiomers was -7.44 to -5.92 kcal/mol with CSP, but -7.15 to -5.87 kcal/mol for SS-stereoisomers. Therefore it is predicted that SS-enantiomer will elute first, followed by SR-antipode. Furthermore, hydrogen bondings, van der Waal's interactions and electrostatic interactions were observed among SR- and SSenantiomers and chiral grooves of CSP. The number of hydrogen bonds was one in each enantiomer binding except S-Ala-R-Tyr, which contained two hydrogen bonds. No hydrogen bond was found in S-Ala-R-Trp, S-Leu-S-Trp, and S-Leu-S-Tyr dipeptides bindings. The chiral recognition mechanisms dictate different strengths of stereoselective bindings of the enantiomers on CSP.展开更多
The insertion reaction mechanism of CBr_2 with CH_3CH_O has been studied by using the B3LYP/6-31G(d) method. The geometries of reactions, transition state and products were completely optimized. All the energy of the ...The insertion reaction mechanism of CBr_2 with CH_3CH_O has been studied by using the B3LYP/6-31G(d) method. The geometries of reactions, transition state and products were completely optimized. All the energy of the species was obtained at the CCSD(T)/6-31G(d) level. All the transition state is verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show that the propionaldehyde (~HP1) is the main product of CH_2 insertion with CH_3CH_O. The calculated results indicated that all the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CBr_2 not only can insert the C_α-H [reaction I(1)]) but also can react with C_β-H [reaction II(1)]. The statistical thermodynamics and Eyring transition state theory with Wigner correc- tion are used to study the thermodynamic and kinetic characters of I(1) and II(1) in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature rang is 250 to 1750 K and 250 to 1600 K at 1.0 atm for I(1) and II(1) respectively. The rate constant and equilibrium constant are distinct in the range from 250 to 1000 K so that I(1) more easily occurs, while the reactions are not selected in the temperature range of 1000-1600展开更多
基金the National Natural Science Foundation of China(Grant Nos.20571037 and 90201018)
文摘Two Mn(II)coordination supramolecules,[Mn2(C8H7O2)4(phen)2(μ-H2O)](1)and [Mn2(btec)(phen)2(H2O)6].2H2O(2)(phen=1,10-phenanthroline,H4btec=1,2,4,5-benzenetetracarboxylic acid),were synthesized by hydrothermal method.The crystal structures of the complexes were determined by X-ray single crystal diffraction.The result indicates that(1)and(2)are both binuclear Mn(II)complexes.The existence of hydrogen bonds makes the binuclear complexes become further connected to coordination su-pramolecules,which possess 1D and 3D infinite structures respectively.The complexes were identified by IR,UV-Vis,surface photovoltage spectrum(SPS)and field-induced surface photovoltage spectrum(FISPS).The results of SPS for the complexes indicate that they both exhibit positive surface photo-voltage response bands in the range of 300―600 nm.The SPS phase spectrum and FISPS of com-plexes indicate that they show certain p-type semiconductor characteristic.However,the intensity,position and number of the SPV response bands are different obviously.The difference of the SPV re-sponse bands is mainly attributed to the different structures of the complexes and the different coor-dination environment of Mn(Ⅱ)in the two complexes.This paper discusses the action of hydrogen bonds in the construction of the supramolecule and the change on the surface photovoltage of com-plex in different coordination environment.
文摘The interaction by hydrogen bond formation of some primary alcohols （ l-heptanol, l-octanol and l-decanol） with esters （methyl methacrylate, ethyl methacrylate and butyl methacrylate） was investigated in non-polar solvents viz., n-heptane, CC14 and benzene by means of FTIR spectroscopy. Formation constants and free energy changes of complex formation were determined. The dependence of the equilibrium constants and free energy changes of complex formation on the alkyl chain length of both the alcohols and esters are discussed. The solvent interaction between the solute and solvent. effect on the hydrogen bond formation is discussed in terms of specific
基金Supported by National National Science Foundation (20464002)
文摘Changes of surface shape, aggregate state, and microstructure of Apocynum fiber before and after irradia-tion were studied by XRD, IR, SEM, ESR, and solid state 13C CP/ MAS NMR. The results show that the surface shape and microstructure were not spoiled under 50 kGy gamma irradiation, while the crystallization of Apocynum fiber changed under 280 kGy . It also shows that different free radicals appear after irradiation and their concentration increases with the increase of irradiation dose.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.20125207,20272066,20333080)the Ministry of Science and Technology of China(Grant No.2003CB716802).
文摘With high association constants in nonpolar solvents, the quadruple hydrogen bonding arrays of 2-ureido-4[1H]-pyrimidinones are recently considered to be one of the ideal building blocks to construct the complicated and functional supramole- cular systems. In this paper, we review the latest achievements of the supramolecular assemblies based on 2-ureido-4[1H]-pyrimidinone AADD quad- ruple hydrogen bonding building blocks.
基金financially supported by National Natural Science Foundation of China(21173212)the Key Research Program of the Chinese Academy of Sciences
文摘The adsorption and dissociation of CH3OH on TiO2 （110） were studied using density functional theory methods. Our results suggest that CH3OH molecules can adsorb up to 3/4 ML （1 ML=5.2× 10^14 molecules/cm2） coverage at five-coordinated titanium （Tisc） sites to form the first layer. In the second layer, the CH3OH is adsorbed at bridge-bonded oxygen, and from the third layer, the CH3OH molecules form a hydrogen-bonded network with each other. The theoretical results show that dissociation of multilayer adsorbed methanol to aldehyde occurs through a stepwise pathway, with easy O-H bond dissociation and rate-determining C-H bond dissociation. The dissociation barriers for 8 or 12 CH3OH molecules on TiO2 are higher than that for low coverage by 0.15-0.21 eV; this suggests that the dissociation of multilayer adsorbed CH3OH is harder.
基金the Department of Science and Technology, New Delhi, India (DST/INT/RFBR/P-147)the Russian Foundation of Basic Research, Russia (RFBR 13-03-92692) for financial assistance
文摘Dipeptides are stereo-specifically involved in several biological functions that are challenging to separate enantiomerically. Elution order of enantiomers is an important issue in chiral chromatography. Amylose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase(CSP) is the best and most-widely-used CSP in chiral separations, but experimental data of enantiomeric separation of dipeptides on this CSP is lacking. Simulation studies were conducted to determine the order of elution and the chiral recognition mechanism of didpetides on this CSP. Results indicated that the docking energy of SR-enantiomers were higher than SS-antipodes. The range of docking energies for SR-enantiomers was -7.44 to -5.92 kcal/mol with CSP, but -7.15 to -5.87 kcal/mol for SS-stereoisomers. Therefore it is predicted that SS-enantiomer will elute first, followed by SR-antipode. Furthermore, hydrogen bondings, van der Waal's interactions and electrostatic interactions were observed among SR- and SSenantiomers and chiral grooves of CSP. The number of hydrogen bonds was one in each enantiomer binding except S-Ala-R-Tyr, which contained two hydrogen bonds. No hydrogen bond was found in S-Ala-R-Trp, S-Leu-S-Trp, and S-Leu-S-Tyr dipeptides bindings. The chiral recognition mechanisms dictate different strengths of stereoselective bindings of the enantiomers on CSP.
基金Supported by the Research Fund of Gangsu Province (Grant No. 0708-11)Tianshui Normal University (Grant No. TSA0604)
文摘The insertion reaction mechanism of CBr_2 with CH_3CH_O has been studied by using the B3LYP/6-31G(d) method. The geometries of reactions, transition state and products were completely optimized. All the energy of the species was obtained at the CCSD(T)/6-31G(d) level. All the transition state is verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show that the propionaldehyde (~HP1) is the main product of CH_2 insertion with CH_3CH_O. The calculated results indicated that all the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CBr_2 not only can insert the C_α-H [reaction I(1)]) but also can react with C_β-H [reaction II(1)]. The statistical thermodynamics and Eyring transition state theory with Wigner correc- tion are used to study the thermodynamic and kinetic characters of I(1) and II(1) in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature rang is 250 to 1750 K and 250 to 1600 K at 1.0 atm for I(1) and II(1) respectively. The rate constant and equilibrium constant are distinct in the range from 250 to 1000 K so that I(1) more easily occurs, while the reactions are not selected in the temperature range of 1000-1600
