The electronic structure and spectra of [Mo3O4-nSn]^(4+)(n=0-4) cations were calculated by means of INDO/CI quantum chemistry method to account for the experimental data of their spectra in water solutions.
Formation and dissociation mechanisms of C-C＋ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environmen...Formation and dissociation mechanisms of C-C＋ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environment, a cytosine monomer is first protonated and then dimerized with an unprotonated cytosine monomer to form a C-C＋ base pair; in an alkaline environment, a protonated cytosine dimer is first unprotonated and then dissociated into two cytosine monomers. In addition, the force for detaching a C-C＋ base pair was found to be inversely proportional to the distance between the two cytosine monomers. These results provide a microscopic mechanism to qualitatively explain the experimentally observed reversible formation and dissociation of i-motifs.展开更多
The structure and energy of the carbonium ions formed upon protonation of butane were studied by the DFT methods. Four stable structures are identified for the protonated form of n-butane, the energy increases in the ...The structure and energy of the carbonium ions formed upon protonation of butane were studied by the DFT methods. Four stable structures are identified for the protonated form of n-butane, the energy increases in the following order： C2HC3〈C1HC2〈C2HH〈C1HH, and the stability decreases in the following order C2HC3〉C1HC2〉C2HH〉C1HH. The stability of the penta-coordinated carbonium ions may be explained by the electron distribution in the three-center-two-electron bonds. The delocalization of the penta-coordinated carbonium ion CHC with three-center-two-electron bonds on positive charges was stronger than that of the penta-coordinated earbonium ion CHH with three-center-two-electron bonds and its stability was higher than that of the penta-coordinated carbonium ion CHH with three-center-two-electron bonds.展开更多
A quantitative interpretation of mass spectra of complex organic compounds so far is notvery perfect and needs some further investigation. In this paper a mechanism of cleft-rate-determining-steps of aromatic conjugat...A quantitative interpretation of mass spectra of complex organic compounds so far is notvery perfect and needs some further investigation. In this paper a mechanism of cleft-rate-determining-steps of aromatic conjugated polyenic acid, methyl benzoate, methyl phenyl ketone,benzonitrile and aniline is proposed, and various quantum parameters of molecular ions ofaromatic conjugated polyenic compounds, together with their framents are calculated bymeans of CNDO/2 method. Through the process of calculation, the peak-height of mass spectracan be quantitatively interpreted, which means that the main factors which influence the cleftforms of simple cleavage of mass spectra of conjugated compounds given by the authorsmight be true to some extent.展开更多
Two new coordination polymers,[Ni(Hpdc)(bib)(H_(2)O)]_(n)(1)and{[Ni(bib)_(3)](ClO_(4))_(2)}_(n)(2),were prepared by mixing Ni^(2+),3,5⁃pyrazoledicarboxylic acid(H3pdc)/p⁃nitrobenzoic acid and 1,4⁃bis(imidazol⁃1⁃ylmeth...Two new coordination polymers,[Ni(Hpdc)(bib)(H_(2)O)]_(n)(1)and{[Ni(bib)_(3)](ClO_(4))_(2)}_(n)(2),were prepared by mixing Ni^(2+),3,5⁃pyrazoledicarboxylic acid(H3pdc)/p⁃nitrobenzoic acid and 1,4⁃bis(imidazol⁃1⁃ylmethyl)butane(bib)by a hydrothermal method,respectively.X⁃ray crystallography reveals a 2D network constructed by six⁃coordinated Ni(Ⅱ)centers,bib,and Hpdc2-ligands in complex 1,while a 2D network is built by Ni(Ⅱ)and bib ligands in 2.Furthermore,the quantum⁃chemical calculations have been performed on‘molecular fragments’extracted from the crystal structure of 1 using the PBE0/LANL2DZ method in Gaussian 16 and the VASP program.CCDC:2343794,1;2343798,2.展开更多
The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data a...The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the triclinic space group Pi with unit cell dimensions a = 7.4509（9）, b = 10.2389（12）, c = 12.2299（15）A, a = 74.771（2）, β = 77.956（2）, 7 = 69.263（2）°, V = 834.98（17） A3 and Z = 2. In order to gain some valuable insights into the molecular structure, the quantum mechanical calculations were performed using both HF and time-dependent density functional theory at the B3LYP/6-31G（d,p） level. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock （HF） and density functional theory （DFT） with the 6-31G（d） basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound was examined using the B3LYP method with the 6-31G（d） basis set. The harmonic vibrational frequencies calculated have been compared with the experimental FTIR and FT-Raman spectra. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance （NMR） calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of the title compound. Moreover, molecular electrostatic potential and thermodynamic parameters of the title compound were investigated by theoretical calculations.展开更多
The emission of NOx during coal combustion contributes to the formation of acid rain and photochemical smog,which would seriously affect the quality of atmospheric environment.Therefore,the decrease of NOx is of great...The emission of NOx during coal combustion contributes to the formation of acid rain and photochemical smog,which would seriously affect the quality of atmospheric environment.Therefore,the decrease of NOx is of great importance for improving the efficient utilization of coal.The present review comprehensively summarized the influence factors and mechanisms of migration and transformation of nitrogen during the coal pyrolysis and combustion based on experimental study and quantum chemical calculation.Firstly,in the process of pyrolysis:the occurrence state and transformation of nitrogen were concluded.The influence of temperature,atmosphere,heating rate and catalyst on formation of NOx precursor and nitrogen migration path at the molecular level were summarized;Secondly,during the process of combustion:the influence of temperature,ambient oxygen concentration,physical structure of coal char,catalyst on heterogeneous oxidation of char(N)were summarized;The effects of char surface properties,catalyst and ambient atmosphere on heterogeneous reduction of NOx were also concluded.Based on the quantum chemical calculation,the reaction path of heterogeneous oxidation of char-N and heterogeneous reduction of NOx were described in detail.Current studies focus more on the generation of HCN and NH3,but in order to reduce the pollution of NOx from the source,it is necessary to further improve the process conditions and the optimal formula of producing more N2 during pyrolysis,as well as clarify the path of the generation of N2.Experiments study and quantum chemistry calculation should be combined to complete the research of directional nitrogen reduction during pyrolysis and denitration during combustion.展开更多
Two new schiff base N,N＇-bis（（2-phenyl-2H-1,2,3-triazol-4-yl）methylene）-1,3-propanediamine （1） and N,N＇-bis（（2-phenyl-2H-1,2,3-triazol-4-yl）methylene） -1,4-butanediamine （2） were synthesized by condensat...Two new schiff base N,N＇-bis（（2-phenyl-2H-1,2,3-triazol-4-yl）methylene）-1,3-propanediamine （1） and N,N＇-bis（（2-phenyl-2H-1,2,3-triazol-4-yl）methylene） -1,4-butanediamine （2） were synthesized by condensation of 2-phenyl-1,2,3-triazole-4-carboxaldehyde with diamine, and characterized by elemental analysis, IR, IH NMR and MS spectra. Their crystal structures were determined by X-ray single crystal diffraction. Both crystals belong to the monoclinic system, space group P21/c. For compound 1（C21H20N8, Mr=384.45）： a = 16.314（3）, b =5.7168（11）, c = 21.316（4） A, β = 105.3（2）°, Z = 4, V = 1917.6（7） A^3, De =1.332 g/cm^3, F（000） = 808,μ = 0.086 mm 1, R = 0.0533 and wR = 0.1460; for compound 2 （C22H22N8, Mr=398.48）： a = 8.6156（17）, b = 5.2964（11）, c = 22.665（5）A, β = 100.54（3）°, Z = 2, V = 1016.8（4） A^3, De= 1.302 g/cm^3, F （000） = 420, μ = 0.083 mm^-1, R = 0.0373 and wR = 0.1155. Based on the crystal data, quantum chemistry calculation was performed on the two title compounds by means of Gaussian 98 program. The molecular orbital energies and atomic net charges population were obtained. Furthermore, we antilyzed their active atoms. The investigation can serve as a theoretical guide to study the synthesis and activity of the title compounds.展开更多
A three-dimensional framework copper（Ⅱ） coordination polymer with copper carbonate basic and 3-（pyridin-2-yl）-1,2,4-triazole （Hpt） has been hydrothemally synthesized.The complex （2,C14 H10 CuN8 ·3H2 O） c...A three-dimensional framework copper（Ⅱ） coordination polymer with copper carbonate basic and 3-（pyridin-2-yl）-1,2,4-triazole （Hpt） has been hydrothemally synthesized.The complex （2,C14 H10 CuN8 ·3H2 O） crystallizes in tetragonal,space group P4 2 /n,a=2.08581（12）,b=2.08581（12）,c=0.72331（4） nm,M r=761.73,V=3.1468（3） nm 3,Dc=1.608 g/cm 3,Z=4,F（000）=1552,GOOF=1.07,R=0.0515 and wR=0.1689.Every asymmetric unit molecular structure of the complex is composed with one copper ion,one and half water molecules and two Hpt molecules.Each copper ion is coordinated with five nitrogen atoms from four Hpt molecules,forming a distorted square pyramidal geometry.The fluorescence spectrum analysis shows that the title complex at room temperature exhibits intense photoluminescence with maximum emission at 450 nm.The quantum chemistry calculation study on the complex has been performed.The stability,some frontier molecular orbital energies and composition characteristics of some frontier molecular orbitals of the complex have been investigated.展开更多
1N-Acetyl-3-（2,4-dichloro-5-fluoro-phenyl）-5-（p-methyl-phenyl）-2-pyrazoline has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray single-crystal diffraction. Ab intio calculations have...1N-Acetyl-3-（2,4-dichloro-5-fluoro-phenyl）-5-（p-methyl-phenyl）-2-pyrazoline has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray single-crystal diffraction. Ab intio calculations have been carded out for the compound by using both B3LYP and HF methods at the 6-31G^＊ basis set. The calculated results show that the predicted geometry can well reproduce the structural parameters. The electronic absorption spectra calculated by B3LYP/6-31G^＊ method are approximate to the experiments and the Natural Bond Orbital （NBO） analyses suggest that the above electronic transitions are mainly assigned to n→π^＊ and π→π^＊ transitions. CIS-HF/6-31G^＊ method is not suitable to predict the electronic spectra for the title compound. The calculation of the second order optical nonlinearity was carded out, giving the value of molecular hyperpolarizability equal to 2.194^＋ 10^-30 esu. On the basis of vibrational analyses, the thermodynamic properties of the compound at different temperature have been calculated, revealing the correlation between C p, m^0, S m^0, H m^0 and temperature.展开更多
Investigating the structures and properties of Au-Ge mixed clusters can give insight into the microscopic mechanisms in gold-catalyzed Ge films and can also provide valuable information for the production of germanium...Investigating the structures and properties of Au-Ge mixed clusters can give insight into the microscopic mechanisms in gold-catalyzed Ge films and can also provide valuable information for the production of germanium-based functional materials. In this work, size-selected anion photoelectron spectroscopy and theoretical calculations were used to explore the structural evolution and electronic properties of Au2Gen^-/0 (n=1-8) clusters. It is found that the two Au atoms in Au2Gen^-/0 (n=1-8) showed high coordination numbers and weak aurophilic interactions. The global minima of Au2Gen- anions and Au2Gen neutrals are in spin doublet and singlet states, respectively. Au2Gen- anions and Au2Gen neutrals showed similar structural features, except for Au2Ge4^-/0 and Au2Ge5^-/0. The C2v symmetric V-shaped structure is observed for Au2Ge1^-/0, while Au2Ge2^-/0 has a C2v symmetric dibridged structure. Au2Ge3^-/0 can be viewed as the two Au atoms attached to different Ge-Ge bonds of Ge3 triangle. Au2Ge4- has two Au atoms edge-capping Ge4 tetrahedron, while Au2Ge4 neutral adopts a C2v symmetric double Au atoms face-capping Ge4 rhombus. Au2Ge5-8^-/0 show triangular, tetragonal, and pentagonal prism-based geometries. Au2Ge6 adopts a C2v symmetric tetragonal prism structure and exhibits σ plus π double bonding characters.展开更多
Binary polyantimony clusters,namely[Cu_(2)Sb_(14)]^(4–) and [Ag_(2)Sb_(14)]^(4–),containing coinage metals,were successfully synthesized and characterized,in which two homoatomic Sb73–subunits are bridged by two co...Binary polyantimony clusters,namely[Cu_(2)Sb_(14)]^(4–) and [Ag_(2)Sb_(14)]^(4–),containing coinage metals,were successfully synthesized and characterized,in which two homoatomic Sb73–subunits are bridged by two coinage metals in η^(4):η^(1) and η^(1):η^(1) coordination modes,respectively.In[M_(2)Sb_(14)]^(4-),two bridging Cu ions and two Sb atoms form a planar rhombic unit,which was revealed to have antiaromatic properties by theoretical calculations.Further electron structure and bonding analysis confirmed the presence of delocalized bonds in the rhombic unit and the metallophilic interaction between two formal M^(+) ions.展开更多
Metal carbides play an important role in catalysis and functional materials.However,the structural characterization of metal carbide clusters has been proven to be a challenging experimental target due to the difficul...Metal carbides play an important role in catalysis and functional materials.However,the structural characterization of metal carbide clusters has been proven to be a challenging experimental target due to the difficulty in size selection.Here we use the size-specific photoelectron velocity-map imaging spectroscopy to study the structures and properties of platinum carbide clusters.Quantum chemical calculations are carried out to identify the structures and to assign the experimental spectra.The results indicate that the cluster size of the chain-to-ring structural evolution for the PtC_(n)^(-)anions occurs at n=14,whereas that for the PtC_(n) neutrals at n=10,revealing a significant effect of charge on the structures of metal carbides.The greatest importance of these building blocks is the strong preference of the Pt atom to expose in the outer side of the chain or ring,exhibiting the active sites for catalyzing potential reactions.These findings provide unique spectroscopic snapshots for the formation and growth of platinum carbide clusters and have important implications in the development of related single-atom catalysts with isolated metal atoms dispersed on supports.展开更多
The knowledge on the ionic structure of YCl_(3)-KCl molten system is of guiding significance for the practical production of yttrium metals and yttrium alloys via molten salt electrolysis using this system as electrol...The knowledge on the ionic structure of YCl_(3)-KCl molten system is of guiding significance for the practical production of yttrium metals and yttrium alloys via molten salt electrolysis using this system as electrolyte.In this paper,the theoretical Raman spectra of the ionic groups which may exist in YCl_(3)-KCl molten system are simulated by quantum chemical calculation using Gaussian09 and Gauss View 5.0 programs based on density functional theory(DFT).Then the ionic structures of 20 mol%-60 mol%YCl_(3)-KCl molten salt systems are studied by comparing the Raman shift values of the bands in the theoretical Raman spectra of different ionic groups with the experimental spectra of this system.YCl_(6)^(3-),Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)are thought to exist in the molten system.With the increase of temperature,the relative content of YCl_(6)^(3-)ionic groups increases while those of Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)ionic groups decrease.Moreover,the"lifetime"of all ionic groups decreases within the temperature range of 692-730℃.Meanwhile,the relative contents of Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)increase with the increase of YCl_(3)content,while that of YCl_(6)^(3-)decreases.The wave function analysis of the four ionic groups(YCl_(6)^(3-),Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-),and Y_(2)Cl_(9)^(3-))is carried out by Multiwfn program.The net charge in each group,the direction of electron migration during the formation of each group,the sites where electrophilic and nucleophilic reactions are most likely to occur in each ionic group,and the order of bond breaking during chemical reactions for the four groups are obtained.展开更多
Four new 14(13→12)-abeolanostane triterpenoids featuring extendedπ-conjugated systems,kadcoccitanes E-H(1-4),were obtained from the stems of Kadsura coccinea through using a HPLC−UV-guided approach.Their structural ...Four new 14(13→12)-abeolanostane triterpenoids featuring extendedπ-conjugated systems,kadcoccitanes E-H(1-4),were obtained from the stems of Kadsura coccinea through using a HPLC−UV-guided approach.Their structural and configurational determination was accomplished through extensive spectroscopic analysis coupled with quantum chemical calculations.Kadcoccitanes E-H were tested for their cytotoxic activities against five human tumor cell lines(HL-60,A-549,SMMC-7721,MDA-MB-231,SW-480)but none of them exhibited activities at the concentration 40μM.展开更多
The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at...The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at B3LYP/6-311＋＋G（d,p） level, and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level. The ionization energies of toluene and the ap- pearance energies for major fragment ions, C7H7＋, C6H5＋, C5H6＋, C5H5＋, are determined to be 8.90, 11.15 or 11.03, 12.72, 13.69, 16.28 eV, respectively, which are all in good agree- ment with published experimental data. With the help of available published experimental data and theoretical results, four dissociative photoionization channels have been proposed： CTHT＋＋H, C6Hs＋＋CH3, C5H6＋WC2H2, CsHs＋＋C2H2＋H. Transition structures and intermediates for those isomerization processes are determined in this work. Especially, the structures of C5H6＋ and C5H5＋ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.展开更多
The G3 and CBS-QB3 theoretical methods are employed to study the decomposition of CF3OH into FCFO and HF by water, water dimmer, and ammonia. The decomposition of CF3OH into FCFO and HF is unlikely to occur in the atm...The G3 and CBS-QB3 theoretical methods are employed to study the decomposition of CF3OH into FCFO and HF by water, water dimmer, and ammonia. The decomposition of CF3OH into FCFO and HF is unlikely to occur in the atmosphere due to the high activated energy of 88.7 k J/mol at the G3 level of theory. However, the computed results predict that the barrier for unimolecular decomposition of CF3OH is decreased to 25.1 kJ/mol from 188.7 k J/mol with the aid of NH3 at the G3 level of theory, which shows that the ammonia play a strong catalytic effect on the split of CF3OH. In addition, the calculated rate constants show that the decomposition of CF3OH by NH3 is faster than those of H2O and the water dimmer by 10^9 and 10^5 times respectively. The rate constants combined with the corresponding concentrations of these species demonstrate that the reaction CF3OH with NH3 via TS4 is of great importance for the decomposition of CF3OH in the atmosphere.展开更多
Quantum mechanics and molecular dynamics are used to simulate guanidinium ionic liquids. Results show that the stronger interaction exists between guanidine cation and chlorine anion with interaction energy about 109....Quantum mechanics and molecular dynamics are used to simulate guanidinium ionic liquids. Results show that the stronger interaction exists between guanidine cation and chlorine anion with interaction energy about 109.216 kcal/mol. There are two types of spatial distribution for the title system： middle and top. Middle mode is a more stable conformation according to energy and geometric distribution. It is also verified by radial distribution function. The continuous increase of carbon dioxide （CO2） does not affect the structure of ionic liquids, but CO2 molecules are always captured by the cavity of ionic liquids.展开更多
Quantum chemical calculations are performed to study the reactions of OH and ozone with- out and with water to estimate whether the single water molecule can decrease the energy barrier of the OH radical reaction with...Quantum chemical calculations are performed to study the reactions of OH and ozone with- out and with water to estimate whether the single water molecule can decrease the energy barrier of the OH radical reaction with ozone. The calculated results demonstrate that the single water molecule can reduce the activated barrier of the naked OH＋Oa reaction with the value of about 4.18 kJ/mol. In addition, the transition state theory is carried out to determine whether the single water molecule could enhance the rate constant of the OH＋O3 reaction. The computed kinetic data indicate that the rate of the ozone reaction with the formed complexes between OH and water is much slower than that of the OH＋O3 reaction, whereas the rate constant of OH reaction with the formed H20---Oa complex is 2 times greater than that of the naked OH radical with ozone reaction. However, these processes in the atmosphere are not important because the reactions can not compete well with the naked reaction of OH with ozone under atmospheric condition.展开更多
The effect of conical intersection on the excited dynamics of benzene is studied by ab initio theory of electronic structure,which provides an important insight into photophysical and photochemical reactions.Based on ...The effect of conical intersection on the excited dynamics of benzene is studied by ab initio theory of electronic structure,which provides an important insight into photophysical and photochemical reactions.Based on the CASSCF(6,6)/6-31+G(d,p)method,the topological structures of conical intersections S_(1)/S and S_(2)/S_(1)of benzene,as well as the optimal structures of the ground state(S)and excited states(S_(1),S_(2)),are determined.The energy minima of the S_(1)state and S_(2)state are estimated at 4.608 e V and 6.889 e V,respectively.In addition,the energy values of the conical intersections of S_(1)/S and S_(2)/S_(1)are predicted to be 5.600 e V and 6.774 e V.According to the topological structures and energy values of the S_(2)/S_(1)and S_(1)/S conical intersections,the photophysical behavior of benzene excited to the S_(2)state and the effects of the S_(2)/S_(1)and S_(1)/S conical intersections are discussed in detail.展开更多
文摘The electronic structure and spectra of [Mo3O4-nSn]^(4+)(n=0-4) cations were calculated by means of INDO/CI quantum chemistry method to account for the experimental data of their spectra in water solutions.
基金Project supported by the National Basic Research Program of China (973 Program,Grant No.2013CB932804)the National Natural Science Foundation of China (Grant Nos.91227115 and 11121403)the Hundred Talent Program of the Chinese Academy of Sciences (CAS)
文摘Formation and dissociation mechanisms of C-C＋ base pairs in acidic and alkaline environments are investigated, employing ab initio quantum chemical calculations. Our calculations suggest that, in an acidic environment, a cytosine monomer is first protonated and then dimerized with an unprotonated cytosine monomer to form a C-C＋ base pair; in an alkaline environment, a protonated cytosine dimer is first unprotonated and then dissociated into two cytosine monomers. In addition, the force for detaching a C-C＋ base pair was found to be inversely proportional to the distance between the two cytosine monomers. These results provide a microscopic mechanism to qualitatively explain the experimentally observed reversible formation and dissociation of i-motifs.
文摘The structure and energy of the carbonium ions formed upon protonation of butane were studied by the DFT methods. Four stable structures are identified for the protonated form of n-butane, the energy increases in the following order： C2HC3〈C1HC2〈C2HH〈C1HH, and the stability decreases in the following order C2HC3〉C1HC2〉C2HH〉C1HH. The stability of the penta-coordinated carbonium ions may be explained by the electron distribution in the three-center-two-electron bonds. The delocalization of the penta-coordinated carbonium ion CHC with three-center-two-electron bonds on positive charges was stronger than that of the penta-coordinated earbonium ion CHH with three-center-two-electron bonds and its stability was higher than that of the penta-coordinated carbonium ion CHH with three-center-two-electron bonds.
文摘A quantitative interpretation of mass spectra of complex organic compounds so far is notvery perfect and needs some further investigation. In this paper a mechanism of cleft-rate-determining-steps of aromatic conjugated polyenic acid, methyl benzoate, methyl phenyl ketone,benzonitrile and aniline is proposed, and various quantum parameters of molecular ions ofaromatic conjugated polyenic compounds, together with their framents are calculated bymeans of CNDO/2 method. Through the process of calculation, the peak-height of mass spectracan be quantitatively interpreted, which means that the main factors which influence the cleftforms of simple cleavage of mass spectra of conjugated compounds given by the authorsmight be true to some extent.
文摘Two new coordination polymers,[Ni(Hpdc)(bib)(H_(2)O)]_(n)(1)and{[Ni(bib)_(3)](ClO_(4))_(2)}_(n)(2),were prepared by mixing Ni^(2+),3,5⁃pyrazoledicarboxylic acid(H3pdc)/p⁃nitrobenzoic acid and 1,4⁃bis(imidazol⁃1⁃ylmethyl)butane(bib)by a hydrothermal method,respectively.X⁃ray crystallography reveals a 2D network constructed by six⁃coordinated Ni(Ⅱ)centers,bib,and Hpdc2-ligands in complex 1,while a 2D network is built by Ni(Ⅱ)and bib ligands in 2.Furthermore,the quantum⁃chemical calculations have been performed on‘molecular fragments’extracted from the crystal structure of 1 using the PBE0/LANL2DZ method in Gaussian 16 and the VASP program.CCDC:2343794,1;2343798,2.
文摘The title compound was synthesized by the base catalyzed reaction of 5-（（quinolin- 8-yloxy）methyl）-1,3,4-oxadiazole-2（3H）-thione with methyl chloroacetate. The structure was supported by the spectroscopic data and unambiguously confirmed by single-crystal X-ray diffraction studies. It crystallizes from a methanol solution in the triclinic space group Pi with unit cell dimensions a = 7.4509（9）, b = 10.2389（12）, c = 12.2299（15）A, a = 74.771（2）, β = 77.956（2）, 7 = 69.263（2）°, V = 834.98（17） A3 and Z = 2. In order to gain some valuable insights into the molecular structure, the quantum mechanical calculations were performed using both HF and time-dependent density functional theory at the B3LYP/6-31G（d,p） level. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree-Fock （HF） and density functional theory （DFT） with the 6-31G（d） basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behavior of the title compound was examined using the B3LYP method with the 6-31G（d） basis set. The harmonic vibrational frequencies calculated have been compared with the experimental FTIR and FT-Raman spectra. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance （NMR） calculation procedure was also performed, and it was used for assigning the 13C and 1H NMR chemical shifts of the title compound. Moreover, molecular electrostatic potential and thermodynamic parameters of the title compound were investigated by theoretical calculations.
基金supported by National Natural Science Foundation of China(21878210)Shanxi “1331”Civil Clean Fuel Engineering Research Center,Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2019L0313)+1 种基金Patent Promotion and implementation in Shanxi Province(20200719)sponsored by Taiyuan Green Coke Energy Co.,Ltd.(China)。
文摘The emission of NOx during coal combustion contributes to the formation of acid rain and photochemical smog,which would seriously affect the quality of atmospheric environment.Therefore,the decrease of NOx is of great importance for improving the efficient utilization of coal.The present review comprehensively summarized the influence factors and mechanisms of migration and transformation of nitrogen during the coal pyrolysis and combustion based on experimental study and quantum chemical calculation.Firstly,in the process of pyrolysis:the occurrence state and transformation of nitrogen were concluded.The influence of temperature,atmosphere,heating rate and catalyst on formation of NOx precursor and nitrogen migration path at the molecular level were summarized;Secondly,during the process of combustion:the influence of temperature,ambient oxygen concentration,physical structure of coal char,catalyst on heterogeneous oxidation of char(N)were summarized;The effects of char surface properties,catalyst and ambient atmosphere on heterogeneous reduction of NOx were also concluded.Based on the quantum chemical calculation,the reaction path of heterogeneous oxidation of char-N and heterogeneous reduction of NOx were described in detail.Current studies focus more on the generation of HCN and NH3,but in order to reduce the pollution of NOx from the source,it is necessary to further improve the process conditions and the optimal formula of producing more N2 during pyrolysis,as well as clarify the path of the generation of N2.Experiments study and quantum chemistry calculation should be combined to complete the research of directional nitrogen reduction during pyrolysis and denitration during combustion.
基金the National Natural Science Foundation(Nos.20461003,20562011)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20050755003)the Trans-Century Training Program Foundation for Talents from the Ministry of Education of China (No. NCET-04-0987).
文摘Two new schiff base N,N＇-bis（（2-phenyl-2H-1,2,3-triazol-4-yl）methylene）-1,3-propanediamine （1） and N,N＇-bis（（2-phenyl-2H-1,2,3-triazol-4-yl）methylene） -1,4-butanediamine （2） were synthesized by condensation of 2-phenyl-1,2,3-triazole-4-carboxaldehyde with diamine, and characterized by elemental analysis, IR, IH NMR and MS spectra. Their crystal structures were determined by X-ray single crystal diffraction. Both crystals belong to the monoclinic system, space group P21/c. For compound 1（C21H20N8, Mr=384.45）： a = 16.314（3）, b =5.7168（11）, c = 21.316（4） A, β = 105.3（2）°, Z = 4, V = 1917.6（7） A^3, De =1.332 g/cm^3, F（000） = 808,μ = 0.086 mm 1, R = 0.0533 and wR = 0.1460; for compound 2 （C22H22N8, Mr=398.48）： a = 8.6156（17）, b = 5.2964（11）, c = 22.665（5）A, β = 100.54（3）°, Z = 2, V = 1016.8（4） A^3, De= 1.302 g/cm^3, F （000） = 420, μ = 0.083 mm^-1, R = 0.0373 and wR = 0.1155. Based on the crystal data, quantum chemistry calculation was performed on the two title compounds by means of Gaussian 98 program. The molecular orbital energies and atomic net charges population were obtained. Furthermore, we antilyzed their active atoms. The investigation can serve as a theoretical guide to study the synthesis and activity of the title compounds.
基金Supported by the Natural Science Foundation of Hunan Province (No. 11JJ9006)Science and Technology Committee of Hengyang (2011kj25)
文摘A three-dimensional framework copper（Ⅱ） coordination polymer with copper carbonate basic and 3-（pyridin-2-yl）-1,2,4-triazole （Hpt） has been hydrothemally synthesized.The complex （2,C14 H10 CuN8 ·3H2 O） crystallizes in tetragonal,space group P4 2 /n,a=2.08581（12）,b=2.08581（12）,c=0.72331（4） nm,M r=761.73,V=3.1468（3） nm 3,Dc=1.608 g/cm 3,Z=4,F（000）=1552,GOOF=1.07,R=0.0515 and wR=0.1689.Every asymmetric unit molecular structure of the complex is composed with one copper ion,one and half water molecules and two Hpt molecules.Each copper ion is coordinated with five nitrogen atoms from four Hpt molecules,forming a distorted square pyramidal geometry.The fluorescence spectrum analysis shows that the title complex at room temperature exhibits intense photoluminescence with maximum emission at 450 nm.The quantum chemistry calculation study on the complex has been performed.The stability,some frontier molecular orbital energies and composition characteristics of some frontier molecular orbitals of the complex have been investigated.
基金supported by the Natural Science Foundation of Shandong Province (No. Z2007B01, Y2007B14)
文摘1N-Acetyl-3-（2,4-dichloro-5-fluoro-phenyl）-5-（p-methyl-phenyl）-2-pyrazoline has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray single-crystal diffraction. Ab intio calculations have been carded out for the compound by using both B3LYP and HF methods at the 6-31G^＊ basis set. The calculated results show that the predicted geometry can well reproduce the structural parameters. The electronic absorption spectra calculated by B3LYP/6-31G^＊ method are approximate to the experiments and the Natural Bond Orbital （NBO） analyses suggest that the above electronic transitions are mainly assigned to n→π^＊ and π→π^＊ transitions. CIS-HF/6-31G^＊ method is not suitable to predict the electronic spectra for the title compound. The calculation of the second order optical nonlinearity was carded out, giving the value of molecular hyperpolarizability equal to 2.194^＋ 10^-30 esu. On the basis of vibrational analyses, the thermodynamic properties of the compound at different temperature have been calculated, revealing the correlation between C p, m^0, S m^0, H m^0 and temperature.
基金supported by the National Natural Science Foundation of China (No.21273246 and No.21103202)the Chinese Academy of Sciences (No.QYZDB-SSW-SLH024)+3 种基金the Natural Science Foundation of Shandong Province of China (No.ZR2018BB040)Open Funds of Beijing National Laboratory for Molecular Sciences (No.BNLMS201804)Research Start-up Funds (Doctoral Science Foundation) of Heze University (No.XY18BS02)Chinese Academy of Sciences President’s International Fellowship Initiative (PIFI) (No.2018VMA0011)
文摘Investigating the structures and properties of Au-Ge mixed clusters can give insight into the microscopic mechanisms in gold-catalyzed Ge films and can also provide valuable information for the production of germanium-based functional materials. In this work, size-selected anion photoelectron spectroscopy and theoretical calculations were used to explore the structural evolution and electronic properties of Au2Gen^-/0 (n=1-8) clusters. It is found that the two Au atoms in Au2Gen^-/0 (n=1-8) showed high coordination numbers and weak aurophilic interactions. The global minima of Au2Gen- anions and Au2Gen neutrals are in spin doublet and singlet states, respectively. Au2Gen- anions and Au2Gen neutrals showed similar structural features, except for Au2Ge4^-/0 and Au2Ge5^-/0. The C2v symmetric V-shaped structure is observed for Au2Ge1^-/0, while Au2Ge2^-/0 has a C2v symmetric dibridged structure. Au2Ge3^-/0 can be viewed as the two Au atoms attached to different Ge-Ge bonds of Ge3 triangle. Au2Ge4- has two Au atoms edge-capping Ge4 tetrahedron, while Au2Ge4 neutral adopts a C2v symmetric double Au atoms face-capping Ge4 rhombus. Au2Ge5-8^-/0 show triangular, tetragonal, and pentagonal prism-based geometries. Au2Ge6 adopts a C2v symmetric tetragonal prism structure and exhibits σ plus π double bonding characters.
基金supported by the National Natural Science Foundation of China(Nos.92161102,22371140 to Z.-M.Sun and 22301143 to L.Qiao)the Fundamental Research Program of Shanxi Province(202103021224028 and 202204021301010 to W.-J.Tian)the Natural Science Foundation of Tianjin City(21JCZXJC00140 to Z.-M.Sun).
文摘Binary polyantimony clusters,namely[Cu_(2)Sb_(14)]^(4–) and [Ag_(2)Sb_(14)]^(4–),containing coinage metals,were successfully synthesized and characterized,in which two homoatomic Sb73–subunits are bridged by two coinage metals in η^(4):η^(1) and η^(1):η^(1) coordination modes,respectively.In[M_(2)Sb_(14)]^(4-),two bridging Cu ions and two Sb atoms form a planar rhombic unit,which was revealed to have antiaromatic properties by theoretical calculations.Further electron structure and bonding analysis confirmed the presence of delocalized bonds in the rhombic unit and the metallophilic interaction between two formal M^(+) ions.
基金supported by the National Natural Science Foundation of China(22273101,22103082,22125303,92061203,and 22288201)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS)(2020187)+3 种基金the Innovation Program for Quantum Science and Technology(2021ZD0303304)Chinese Academy of Sciences(GJJSTD20220001)Dalian Institute of Chemical Physics(DICP DCLS201702)K.C.Wong Education Foundation(GJTD-201806)。
文摘Metal carbides play an important role in catalysis and functional materials.However,the structural characterization of metal carbide clusters has been proven to be a challenging experimental target due to the difficulty in size selection.Here we use the size-specific photoelectron velocity-map imaging spectroscopy to study the structures and properties of platinum carbide clusters.Quantum chemical calculations are carried out to identify the structures and to assign the experimental spectra.The results indicate that the cluster size of the chain-to-ring structural evolution for the PtC_(n)^(-)anions occurs at n=14,whereas that for the PtC_(n) neutrals at n=10,revealing a significant effect of charge on the structures of metal carbides.The greatest importance of these building blocks is the strong preference of the Pt atom to expose in the outer side of the chain or ring,exhibiting the active sites for catalyzing potential reactions.These findings provide unique spectroscopic snapshots for the formation and growth of platinum carbide clusters and have important implications in the development of related single-atom catalysts with isolated metal atoms dispersed on supports.
基金financially supported by the National Natural Science Foundation of China (No.51974081)the Fundamental Research Funds for the Central Universities (No.N2225045)MOE of China and WEIQIAO Industry-Education Cooperation Project (No.2021021800102)。
文摘The knowledge on the ionic structure of YCl_(3)-KCl molten system is of guiding significance for the practical production of yttrium metals and yttrium alloys via molten salt electrolysis using this system as electrolyte.In this paper,the theoretical Raman spectra of the ionic groups which may exist in YCl_(3)-KCl molten system are simulated by quantum chemical calculation using Gaussian09 and Gauss View 5.0 programs based on density functional theory(DFT).Then the ionic structures of 20 mol%-60 mol%YCl_(3)-KCl molten salt systems are studied by comparing the Raman shift values of the bands in the theoretical Raman spectra of different ionic groups with the experimental spectra of this system.YCl_(6)^(3-),Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)are thought to exist in the molten system.With the increase of temperature,the relative content of YCl_(6)^(3-)ionic groups increases while those of Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)ionic groups decrease.Moreover,the"lifetime"of all ionic groups decreases within the temperature range of 692-730℃.Meanwhile,the relative contents of Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-)and Y_(2)Cl_(9)^(3-)increase with the increase of YCl_(3)content,while that of YCl_(6)^(3-)decreases.The wave function analysis of the four ionic groups(YCl_(6)^(3-),Y_(2)Cl_(7)^(-),Y_(2)Cl_(8)^(2-),and Y_(2)Cl_(9)^(3-))is carried out by Multiwfn program.The net charge in each group,the direction of electron migration during the formation of each group,the sites where electrophilic and nucleophilic reactions are most likely to occur in each ionic group,and the order of bond breaking during chemical reactions for the four groups are obtained.
基金Natural Science Foundation of Yunnan Province(202101AT070188).
文摘Four new 14(13→12)-abeolanostane triterpenoids featuring extendedπ-conjugated systems,kadcoccitanes E-H(1-4),were obtained from the stems of Kadsura coccinea through using a HPLC−UV-guided approach.Their structural and configurational determination was accomplished through extensive spectroscopic analysis coupled with quantum chemical calculations.Kadcoccitanes E-H were tested for their cytotoxic activities against five human tumor cell lines(HL-60,A-549,SMMC-7721,MDA-MB-231,SW-480)but none of them exhibited activities at the concentration 40μM.
文摘The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at B3LYP/6-311＋＋G（d,p） level, and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level. The ionization energies of toluene and the ap- pearance energies for major fragment ions, C7H7＋, C6H5＋, C5H6＋, C5H5＋, are determined to be 8.90, 11.15 or 11.03, 12.72, 13.69, 16.28 eV, respectively, which are all in good agree- ment with published experimental data. With the help of available published experimental data and theoretical results, four dissociative photoionization channels have been proposed： CTHT＋＋H, C6Hs＋＋CH3, C5H6＋WC2H2, CsHs＋＋C2H2＋H. Transition structures and intermediates for those isomerization processes are determined in this work. Especially, the structures of C5H6＋ and C5H5＋ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.
基金This work was supported by the National Natural Science Foundation of China （No.10865003） and the Guizhou University for Nationalities （2010）. The authors thank professors W. T. Duncan, R. L. Bell, and T. N. Truong or providing the rate program through the internet.
文摘The G3 and CBS-QB3 theoretical methods are employed to study the decomposition of CF3OH into FCFO and HF by water, water dimmer, and ammonia. The decomposition of CF3OH into FCFO and HF is unlikely to occur in the atmosphere due to the high activated energy of 88.7 k J/mol at the G3 level of theory. However, the computed results predict that the barrier for unimolecular decomposition of CF3OH is decreased to 25.1 kJ/mol from 188.7 k J/mol with the aid of NH3 at the G3 level of theory, which shows that the ammonia play a strong catalytic effect on the split of CF3OH. In addition, the calculated rate constants show that the decomposition of CF3OH by NH3 is faster than those of H2O and the water dimmer by 10^9 and 10^5 times respectively. The rate constants combined with the corresponding concentrations of these species demonstrate that the reaction CF3OH with NH3 via TS4 is of great importance for the decomposition of CF3OH in the atmosphere.
基金ACKNOWLEDGMENTS This work was supported by the Open Project Program of Key Laboratory of Theoretical Chemistry and Molecular Simulation of Ministry of Education, Hunan University of Science and Technology, China （No.E21104）, the National Natural Science Foundation of China （No.21201062 and No.21172066）, and the International Cooperation Project （No.2013DFG60060）.
文摘Quantum mechanics and molecular dynamics are used to simulate guanidinium ionic liquids. Results show that the stronger interaction exists between guanidine cation and chlorine anion with interaction energy about 109.216 kcal/mol. There are two types of spatial distribution for the title system： middle and top. Middle mode is a more stable conformation according to energy and geometric distribution. It is also verified by radial distribution function. The continuous increase of carbon dioxide （CO2） does not affect the structure of ionic liquids, but CO2 molecules are always captured by the cavity of ionic liquids.
基金This work was supported by the National Natural Science Foundation of China （No.10865003） and the Science and Technology Foundation of GuiZhou Province, China （No.[201112107）. We thank the Key Laboratory of Guizhou High Performance Computational Chemistry for computer time.
文摘Quantum chemical calculations are performed to study the reactions of OH and ozone with- out and with water to estimate whether the single water molecule can decrease the energy barrier of the OH radical reaction with ozone. The calculated results demonstrate that the single water molecule can reduce the activated barrier of the naked OH＋Oa reaction with the value of about 4.18 kJ/mol. In addition, the transition state theory is carried out to determine whether the single water molecule could enhance the rate constant of the OH＋O3 reaction. The computed kinetic data indicate that the rate of the ozone reaction with the formed complexes between OH and water is much slower than that of the OH＋O3 reaction, whereas the rate constant of OH reaction with the formed H20---Oa complex is 2 times greater than that of the naked OH radical with ozone reaction. However, these processes in the atmosphere are not important because the reactions can not compete well with the naked reaction of OH with ozone under atmospheric condition.
基金Project supported by the National Key Research and Development Program of China(Grant No.2019YFA0307700)the National Natural Science Foundation of China(Grant Nos.11974381,11674355,and 21773299)。
文摘The effect of conical intersection on the excited dynamics of benzene is studied by ab initio theory of electronic structure,which provides an important insight into photophysical and photochemical reactions.Based on the CASSCF(6,6)/6-31+G(d,p)method,the topological structures of conical intersections S_(1)/S and S_(2)/S_(1)of benzene,as well as the optimal structures of the ground state(S)and excited states(S_(1),S_(2)),are determined.The energy minima of the S_(1)state and S_(2)state are estimated at 4.608 e V and 6.889 e V,respectively.In addition,the energy values of the conical intersections of S_(1)/S and S_(2)/S_(1)are predicted to be 5.600 e V and 6.774 e V.According to the topological structures and energy values of the S_(2)/S_(1)and S_(1)/S conical intersections,the photophysical behavior of benzene excited to the S_(2)state and the effects of the S_(2)/S_(1)and S_(1)/S conical intersections are discussed in detail.
