In the given research,the molecular structures of two new compounds,4-((E)-3-(dimethylamino)styryl)-6-((E)-4-(dimethylamino)styryl)pyrimidine-2-amine(PM-1)and N-(4-((E)-3-(dimethylamino)styryl)-6-((E)-4-(dimethylamino...In the given research,the molecular structures of two new compounds,4-((E)-3-(dimethylamino)styryl)-6-((E)-4-(dimethylamino)styryl)pyrimidine-2-amine(PM-1)and N-(4-((E)-3-(dimethylamino)styryl)-6-((E)-4-(dimethylamino)styryl)pyrimidine-2-yl)-4,6-dichloro 1,3,5-1,3,5-triazin-2-amine(PM-2),have been studied with the use of density functional theory(DFT/B3LYP/MidiX)in dimethylformamide(DMF)for the first time.The electronic spectra of the new compounds in a DMF solvent were carried out by temporally dependent density functional theory(TD-DFT)method.The computed absorption spectral data of the title compounds are in good agreement with the experimental data,thus allowing an assignment of the UV/Vis spectra.The equilibrium geometry,the HOMO and LUMO molecular orbitals,excitation energies,oscillator strengths and Natural Bond Orbital(NBO)analysis for the molecules have also been calculated and presented.FT-IR spectra of the title molecules are recorded and discussed.The electron location function(ELF),localized orbital locator(LOL)and quantum theory of atoms in molecules(QTAIM)analyses were also carried out.On the basis of polyvinyl alcohol(PVA)and synthesized molecules,polarizer for UV/Vis region of the spectrum has been developed.展开更多
Substances known as nitrogen mustards turn into aziridinium ion through the intramolecular cyclization SN1. This ion reacts with the DNA preferably at the N7 position of the guanine, and because of this, it is an impo...Substances known as nitrogen mustards turn into aziridinium ion through the intramolecular cyclization SN1. This ion reacts with the DNA preferably at the N7 position of the guanine, and because of this, it is an important antineoplastic agent. Based on this, the objective of this study is to quantify the interaction between the nitrogen mustard mechlorethamine and the guanine, using the NBO analysis and the QTAIM theory. The results of the NBO analysis showed that when the triangular cycle C4-N1-C5 is formed, there is some resonance among these atoms. This analysis also showed that the electronic transition at the sigma antibondingorbital σ* N1-C4 presents higher perturbation energy of second order, indicating that this bond is broken at the nucleophilic attack of the N7 nitrogen of guanine. The analysis that refers to the electron density obtained by the QTAIM theory indicates that the guanine proximity enables an electron density polarization of the BCPs aziridinium ion of mechlorethamine making that the frontal part of the ion becomes electron deficient. Finally, the relative results to the Laplacian of the electron density obtained by the QTAIM theory showed that the guanine approximation increases the “hole” factor at the C4, proving that the nucleophilic attack based on the “lump-hole” concept causes the region of that atom is the site of alkylation reaction.展开更多
Using the first-principles calculations based on spin density functional theory（DFT）, we investigate the structure,elastic properties, and electronic structure of Pnnm-CrB4. It is found that Pnnm-CrB4 is thermodynam...Using the first-principles calculations based on spin density functional theory（DFT）, we investigate the structure,elastic properties, and electronic structure of Pnnm-CrB4. It is found that Pnnm-CrB4 is thermodynamically and mechanically stable. The calculated elastic properties such as the bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio indicate that CrB4 is an incompressible material. Vicker＇s hardness of Pnnm-CrB4 is estimated to be 26.3 GPa, which is in good agreement with the experimental values. The analysis of the investigated electronic properties shows that PnnmCrB4 has the metallic character and there exist strong B–B and Cr–B bonds in the compound, which are further confirmed by Bader＇s quantum theory of atoms in molecules（QTAIM）. Thermodynamic properties are also investigated.展开更多
采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而...采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而当空穴尺寸相对大时,配合物则采取扭曲结构以降低体系能量。当配体相同时,随着铀、镎、钚变化,An=O伸缩振动频率逐渐变小,这与优化的键长和键级变化规律相一致。QTAIM(quantum theory of atoms in molecule)拓扑分析显示An-N为弱共价单键特征,具有较大离子性成分。依据不同铀源,得到与大环配体的反应自由能均小于146 kJ·mol^(-1),与实验合成配合物的反应能计算数值相当。对含铀配合物电子吸收光谱计算显示,低能(近红外和可见光区)的吸收带具有全部或较大的配体→金属电荷转移性质贡献。展开更多
使用密度泛函理论(B3LYP)方法,结合准相对论有效核势(ECP)和二分量ZORA相对论Hamiltonian,探索三明治型四聚吡咯铀配合物LUmL'(配体为porphyrizine或porphyrine;m=III和IV)的结构、成键和反应性质。优化多种空间和"电子自旋态&...使用密度泛函理论(B3LYP)方法,结合准相对论有效核势(ECP)和二分量ZORA相对论Hamiltonian,探索三明治型四聚吡咯铀配合物LUmL'(配体为porphyrizine或porphyrine;m=III和IV)的结构、成键和反应性质。优化多种空间和"电子自旋态"异构体结构,发现铀配合物具有交叉式、高电子自旋态的基态。QTAIM(Quantum theory of atoms in molecule)的U-N键临界点处的电子/能量密度拓扑分析以及counterpoise计算U-N作用能,揭示该化学键为弱极性共价键。计算显示在采用适当的三价和四价铀源和强碱性配体时,可经过放热反应生成配合物。考虑溶剂(苯、THF和水)和旋-轨耦合影响,计算从四价铀配合物到三价的还原电势,得到数值均小于1 V,这与四价配合物相对稳定、三价铀配合物具有强还原性的实验结果相符合。研究发现降低溶剂极性,配合物的还原电势向负方向移动,这可为实验中采用溶剂极性来调控配合物的氧化还原性质提供理论指导。展开更多
为探索四聚吡咯配体和低价铀离子相互作用,以实验合成单层三明治结构配合物PcU~ⅥPc(Pc=酞菁)为基础,设计双层三明治型PzU^mPzU^mPz(m=Ⅲ,Ⅳ,Pz=氮杂卟啉),采用相对论密度泛函理论考察了其几何结构、异构体相对稳定性以及成键和轨道性质...为探索四聚吡咯配体和低价铀离子相互作用,以实验合成单层三明治结构配合物PcU~ⅥPc(Pc=酞菁)为基础,设计双层三明治型PzU^mPzU^mPz(m=Ⅲ,Ⅳ,Pz=氮杂卟啉),采用相对论密度泛函理论考察了其几何结构、异构体相对稳定性以及成键和轨道性质.得到se(staggered-eclipsed)和es(eclipsed-staggered)2种类型稳定空间异构体,并进一步优化其所有可能的电子自旋态异构体.计算结果表明,这些低价铀配合物均具有五重态基态.分子中的原子量子理论(quantum theory of atoms in molecule,QTAIM)在U—N键临界点处的电子/能量密度拓扑分析显示U—N键为弱极性共价键.四价配合物拥有4个U(5f)性质高能占据轨道,与2个U4+的5f单电子数相一致;而三价配合物有很大配体参与作用.2个铀原子和中间Pz配体质心近似成线性,这与配合物具有稳定的σ(U—U)成键轨道密切相关.展开更多
In this report, different models of bonding and structure such as Lewis, VSEPR, Ligand close packing (LCP), VB, qualitative MO and QTAIM have been applied to analyze the Bonds and structures of two equilibrium geometr...In this report, different models of bonding and structure such as Lewis, VSEPR, Ligand close packing (LCP), VB, qualitative MO and QTAIM have been applied to analyze the Bonds and structures of two equilibrium geometries (planar D2h and perpendicular D2d) of C2H42+. The geometries were optimized at near RHF and MP2 limit using ccpVTZ basis set. While the above bonding models are successfully applied for predicting the low energy isomers of molecules, prior to solving the Schr?dinger equation, it is shown that the cited models fail in predicting the existence of perpendicular, D2d form of C2H42+. In this regard the interpretations of significant energetic stabilization of D2d form over planar isomer has also been revisited. This is attributed to the hidden effect of the Pauli Exclusion principle.展开更多
A theoretical study of hydride bonds formed between beryllium hydride and alkaline earth metal cations is presented. B3LYP/6-311++G(d,p) calculations were used for determining the optimized geometries of the BeH2...K+...A theoretical study of hydride bonds formed between beryllium hydride and alkaline earth metal cations is presented. B3LYP/6-311++G(d,p) calculations were used for determining the optimized geometries of the BeH2...K+, BeH2...Ca+2, BeH2...K+...BeH2, and BeH2...Ca+2...BeH2 hydride-bonded complexes, where among them the first are binaries, whereas the last ones are ternaries with the calcium (Ca+2) and potassium (K+) ions mediating the interactions with the beryllium hydride (BeH2). A detailed structural analysis were performed, by which the yielded profiles are in good agreement with results of the infrared vibrational spectrum, mainly in regards to the existence of red-shifted modes followed by enlarged absorption intensity ratios of the B-H bonds of the binary complexes. The capability of either donating or accepting of protons among BeH2, K+, and Ca+2, is currently treated in conformity with Lewis’s acid/base theory, but is also interpreted through the application of the Quantum Theory of Atoms in Molecules (QTAIM), whose formalism consents in the molecular modeling of concentrations and depletions of charge density ruled by the Laplacian shapes, charge transference fluxes, as well as by the local virial theorem of the electronic density with quantification of the kinetic and potential energies along the bonds and interactions.展开更多
在UB3LYP/6-311++G(3df,3pd)水平下,详细研究了Ni活化NH3分子的单重态和三重态势能面,并用分子中的原子量子理论(Quantum Theory of Atom-in-Molecular,QTAIM)计算了势能面上所有驻点的性质.计算结果表明,单重态势能面有两条反应途径,...在UB3LYP/6-311++G(3df,3pd)水平下,详细研究了Ni活化NH3分子的单重态和三重态势能面,并用分子中的原子量子理论(Quantum Theory of Atom-in-Molecular,QTAIM)计算了势能面上所有驻点的性质.计算结果表明,单重态势能面有两条反应途径,而三重态势能面仅有一条反应途径.第一个N-H断开的活化能较低,为99.96kJ/mol,活化自由能为100.86kJ/mol,在常温下就可以进行;第二个N-H键断裂所需能量高达200kJ/mol,不容易进行.在合适温度下,Ni可以活化NH3得到三重态HNiNH2,这表明Ni可以作为活化NH3分子的良好催化剂.展开更多
The energies, geometries and harmonic vibrational frequencies of 1 ： 1 5-hydroxytryptamine-water （5-HT-H20） complexes are studied at the MP2/6-311 ＋ ＋ G（d,p） level. Natural bond orbital （NBO）, quantum theory ...The energies, geometries and harmonic vibrational frequencies of 1 ： 1 5-hydroxytryptamine-water （5-HT-H20） complexes are studied at the MP2/6-311 ＋ ＋ G（d,p） level. Natural bond orbital （NBO）, quantum theory of atoms in molecules （QTAIM） analyses and the localized molecular orbital energy decomposition analysis （LMO-EDA） were performed to explore the nature of the hydrogen-bonding interactions in these complexes. Various types of hydro- gen bonds （H-bonds） are formed in these 5-HT-H20 complexes. The intermolecular C4H55HT＇＂Ow H-bond in HTW3 is strengthened due to the cooperativity, whereas no such cooperativity is found in the other 5-HT-H20 complexes. H-bond in which nitrogen atom of amino in 5-HT acted as proton donors was stronger than other H-bonds. Our researches show that the hydrogen bonding interaction plays a vital role on the relative stabilities of 5-HT-H20 complexes.展开更多
经三十余年努力,二价铀溶液化学于近年取得突破性进展,Evans和Meyer等成功获得两个可通过X-ray晶体衍射表征结构的有机金属铀(Ⅱ)配合物.为进一步拓展U~Ⅱ配合物化学和探索可能存在的金属多重键,设计双核配合物[(U~Ⅱ)_2(L)](L为八齿氮...经三十余年努力,二价铀溶液化学于近年取得突破性进展,Evans和Meyer等成功获得两个可通过X-ray晶体衍射表征结构的有机金属铀(Ⅱ)配合物.为进一步拓展U~Ⅱ配合物化学和探索可能存在的金属多重键,设计双核配合物[(U~Ⅱ)_2(L)](L为八齿氮供体低聚吡咯大环四价阴离子),并使用相对论密度泛函理论优化其可能的电子自旋态异构体结构和计算相关性质.结果表明,[(U~Ⅱ)_2(L)]具有三重态基态,其电子组态为π~4σ~2δ~2;U(5f)原子轨道对高占据分子轨道有重要贡献;它的U—U键长为2.33?、Mayer键级为3.89和对应的伸缩振动频率为259 cm^(–1),被指认为U—U弱四重键.这一结论与QTAIM(quantum theory of atoms in molecule)的U—U键临界点处的电子/能量密度拓扑分析结果相一致.与不同氧化态铀同类物[(U^m)_2(L)]^(n+)(m=ⅡI,n=2;m=IV,n=4)比较显示,随着铀氧化态增大,U—U距离增长、键级变小、伸缩振动频率变小,金属铀电子自旋密度与常规预期值的差值(?SU)增大;结合分子轨道和QTAIM参数分析,发现金属氧化态可以调控配体和金属轨道能级匹配程度和改变金属-金属多重键.展开更多
The intermolecular interactions in the dimers of m-nisoldipine polymorphism were studied by B3LYP calculations and quantum theory of ＂atoms in molecules＂ （QTAIM） studies. Four geometries of dimers were obtained： ...The intermolecular interactions in the dimers of m-nisoldipine polymorphism were studied by B3LYP calculations and quantum theory of ＂atoms in molecules＂ （QTAIM） studies. Four geometries of dimers were obtained： dimer I （a：dimer, O…H--N）, dimer II （b-dimer, O…H--N）, dimer III （b-dimer, n-stacking-c）, and dimer IV （b-dimer, n-stacking-p）. The interaction energies of the four dimers are along the sequence of II〉I〉III〉IV. The intermolecular distance of the interactions follows the order： I （O…H--N）〈II （O…H--N）, and III （n-stacking）〈 IV （n-stacking）. Both the O…H--N hydrogen-bonding and n-stacking interactions belong to weak non-covalent interactions. The O…H--N hydrogen-bonding interactions with more electrostatic characters are stronger than the n-stacking interactions. The strength of the weak interactions decreases in the order： I〉II〉III〉IV, and the electrostatic character decreases along the sequence： I〉II〉III〉IV.展开更多
基金supported by the National Academy of Sciences of Belarus
文摘In the given research,the molecular structures of two new compounds,4-((E)-3-(dimethylamino)styryl)-6-((E)-4-(dimethylamino)styryl)pyrimidine-2-amine(PM-1)and N-(4-((E)-3-(dimethylamino)styryl)-6-((E)-4-(dimethylamino)styryl)pyrimidine-2-yl)-4,6-dichloro 1,3,5-1,3,5-triazin-2-amine(PM-2),have been studied with the use of density functional theory(DFT/B3LYP/MidiX)in dimethylformamide(DMF)for the first time.The electronic spectra of the new compounds in a DMF solvent were carried out by temporally dependent density functional theory(TD-DFT)method.The computed absorption spectral data of the title compounds are in good agreement with the experimental data,thus allowing an assignment of the UV/Vis spectra.The equilibrium geometry,the HOMO and LUMO molecular orbitals,excitation energies,oscillator strengths and Natural Bond Orbital(NBO)analysis for the molecules have also been calculated and presented.FT-IR spectra of the title molecules are recorded and discussed.The electron location function(ELF),localized orbital locator(LOL)and quantum theory of atoms in molecules(QTAIM)analyses were also carried out.On the basis of polyvinyl alcohol(PVA)and synthesized molecules,polarizer for UV/Vis region of the spectrum has been developed.
文摘Substances known as nitrogen mustards turn into aziridinium ion through the intramolecular cyclization SN1. This ion reacts with the DNA preferably at the N7 position of the guanine, and because of this, it is an important antineoplastic agent. Based on this, the objective of this study is to quantify the interaction between the nitrogen mustard mechlorethamine and the guanine, using the NBO analysis and the QTAIM theory. The results of the NBO analysis showed that when the triangular cycle C4-N1-C5 is formed, there is some resonance among these atoms. This analysis also showed that the electronic transition at the sigma antibondingorbital σ* N1-C4 presents higher perturbation energy of second order, indicating that this bond is broken at the nucleophilic attack of the N7 nitrogen of guanine. The analysis that refers to the electron density obtained by the QTAIM theory indicates that the guanine proximity enables an electron density polarization of the BCPs aziridinium ion of mechlorethamine making that the frontal part of the ion becomes electron deficient. Finally, the relative results to the Laplacian of the electron density obtained by the QTAIM theory showed that the guanine approximation increases the “hole” factor at the C4, proving that the nucleophilic attack based on the “lump-hole” concept causes the region of that atom is the site of alkylation reaction.
基金Project supported by the National Natural Science Foundation of China(Grant No.U1304111)Program for Science&Technology Innovation Talents in Universities of Henan Province,China(Grant No.14HASTIT039)the Innovation Team of Henan University of Science and Technology,China(Grant No.2015XTD001)
文摘Using the first-principles calculations based on spin density functional theory（DFT）, we investigate the structure,elastic properties, and electronic structure of Pnnm-CrB4. It is found that Pnnm-CrB4 is thermodynamically and mechanically stable. The calculated elastic properties such as the bulk modulus, shear modulus, Young＇s modulus, and Poisson＇s ratio indicate that CrB4 is an incompressible material. Vicker＇s hardness of Pnnm-CrB4 is estimated to be 26.3 GPa, which is in good agreement with the experimental values. The analysis of the investigated electronic properties shows that PnnmCrB4 has the metallic character and there exist strong B–B and Cr–B bonds in the compound, which are further confirmed by Bader＇s quantum theory of atoms in molecules（QTAIM）. Thermodynamic properties are also investigated.
基金supported by the National Natural Science Foundation of China(21073013,91026000,91226105)Chinese Academy of Sciences Hundred Talent Program(Y2291810S3)~~
文摘采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而当空穴尺寸相对大时,配合物则采取扭曲结构以降低体系能量。当配体相同时,随着铀、镎、钚变化,An=O伸缩振动频率逐渐变小,这与优化的键长和键级变化规律相一致。QTAIM(quantum theory of atoms in molecule)拓扑分析显示An-N为弱共价单键特征,具有较大离子性成分。依据不同铀源,得到与大环配体的反应自由能均小于146 kJ·mol^(-1),与实验合成配合物的反应能计算数值相当。对含铀配合物电子吸收光谱计算显示,低能(近红外和可见光区)的吸收带具有全部或较大的配体→金属电荷转移性质贡献。
文摘使用密度泛函理论(B3LYP)方法,结合准相对论有效核势(ECP)和二分量ZORA相对论Hamiltonian,探索三明治型四聚吡咯铀配合物LUmL'(配体为porphyrizine或porphyrine;m=III和IV)的结构、成键和反应性质。优化多种空间和"电子自旋态"异构体结构,发现铀配合物具有交叉式、高电子自旋态的基态。QTAIM(Quantum theory of atoms in molecule)的U-N键临界点处的电子/能量密度拓扑分析以及counterpoise计算U-N作用能,揭示该化学键为弱极性共价键。计算显示在采用适当的三价和四价铀源和强碱性配体时,可经过放热反应生成配合物。考虑溶剂(苯、THF和水)和旋-轨耦合影响,计算从四价铀配合物到三价的还原电势,得到数值均小于1 V,这与四价配合物相对稳定、三价铀配合物具有强还原性的实验结果相符合。研究发现降低溶剂极性,配合物的还原电势向负方向移动,这可为实验中采用溶剂极性来调控配合物的氧化还原性质提供理论指导。
文摘为探索四聚吡咯配体和低价铀离子相互作用,以实验合成单层三明治结构配合物PcU~ⅥPc(Pc=酞菁)为基础,设计双层三明治型PzU^mPzU^mPz(m=Ⅲ,Ⅳ,Pz=氮杂卟啉),采用相对论密度泛函理论考察了其几何结构、异构体相对稳定性以及成键和轨道性质.得到se(staggered-eclipsed)和es(eclipsed-staggered)2种类型稳定空间异构体,并进一步优化其所有可能的电子自旋态异构体.计算结果表明,这些低价铀配合物均具有五重态基态.分子中的原子量子理论(quantum theory of atoms in molecule,QTAIM)在U—N键临界点处的电子/能量密度拓扑分析显示U—N键为弱极性共价键.四价配合物拥有4个U(5f)性质高能占据轨道,与2个U4+的5f单电子数相一致;而三价配合物有很大配体参与作用.2个铀原子和中间Pz配体质心近似成线性,这与配合物具有稳定的σ(U—U)成键轨道密切相关.
文摘In this report, different models of bonding and structure such as Lewis, VSEPR, Ligand close packing (LCP), VB, qualitative MO and QTAIM have been applied to analyze the Bonds and structures of two equilibrium geometries (planar D2h and perpendicular D2d) of C2H42+. The geometries were optimized at near RHF and MP2 limit using ccpVTZ basis set. While the above bonding models are successfully applied for predicting the low energy isomers of molecules, prior to solving the Schr?dinger equation, it is shown that the cited models fail in predicting the existence of perpendicular, D2d form of C2H42+. In this regard the interpretations of significant energetic stabilization of D2d form over planar isomer has also been revisited. This is attributed to the hidden effect of the Pauli Exclusion principle.
文摘A theoretical study of hydride bonds formed between beryllium hydride and alkaline earth metal cations is presented. B3LYP/6-311++G(d,p) calculations were used for determining the optimized geometries of the BeH2...K+, BeH2...Ca+2, BeH2...K+...BeH2, and BeH2...Ca+2...BeH2 hydride-bonded complexes, where among them the first are binaries, whereas the last ones are ternaries with the calcium (Ca+2) and potassium (K+) ions mediating the interactions with the beryllium hydride (BeH2). A detailed structural analysis were performed, by which the yielded profiles are in good agreement with results of the infrared vibrational spectrum, mainly in regards to the existence of red-shifted modes followed by enlarged absorption intensity ratios of the B-H bonds of the binary complexes. The capability of either donating or accepting of protons among BeH2, K+, and Ca+2, is currently treated in conformity with Lewis’s acid/base theory, but is also interpreted through the application of the Quantum Theory of Atoms in Molecules (QTAIM), whose formalism consents in the molecular modeling of concentrations and depletions of charge density ruled by the Laplacian shapes, charge transference fluxes, as well as by the local virial theorem of the electronic density with quantification of the kinetic and potential energies along the bonds and interactions.
文摘在UB3LYP/6-311++G(3df,3pd)水平下,详细研究了Ni活化NH3分子的单重态和三重态势能面,并用分子中的原子量子理论(Quantum Theory of Atom-in-Molecular,QTAIM)计算了势能面上所有驻点的性质.计算结果表明,单重态势能面有两条反应途径,而三重态势能面仅有一条反应途径.第一个N-H断开的活化能较低,为99.96kJ/mol,活化自由能为100.86kJ/mol,在常温下就可以进行;第二个N-H键断裂所需能量高达200kJ/mol,不容易进行.在合适温度下,Ni可以活化NH3得到三重态HNiNH2,这表明Ni可以作为活化NH3分子的良好催化剂.
文摘The energies, geometries and harmonic vibrational frequencies of 1 ： 1 5-hydroxytryptamine-water （5-HT-H20） complexes are studied at the MP2/6-311 ＋ ＋ G（d,p） level. Natural bond orbital （NBO）, quantum theory of atoms in molecules （QTAIM） analyses and the localized molecular orbital energy decomposition analysis （LMO-EDA） were performed to explore the nature of the hydrogen-bonding interactions in these complexes. Various types of hydro- gen bonds （H-bonds） are formed in these 5-HT-H20 complexes. The intermolecular C4H55HT＇＂Ow H-bond in HTW3 is strengthened due to the cooperativity, whereas no such cooperativity is found in the other 5-HT-H20 complexes. H-bond in which nitrogen atom of amino in 5-HT acted as proton donors was stronger than other H-bonds. Our researches show that the hydrogen bonding interaction plays a vital role on the relative stabilities of 5-HT-H20 complexes.
文摘经三十余年努力,二价铀溶液化学于近年取得突破性进展,Evans和Meyer等成功获得两个可通过X-ray晶体衍射表征结构的有机金属铀(Ⅱ)配合物.为进一步拓展U~Ⅱ配合物化学和探索可能存在的金属多重键,设计双核配合物[(U~Ⅱ)_2(L)](L为八齿氮供体低聚吡咯大环四价阴离子),并使用相对论密度泛函理论优化其可能的电子自旋态异构体结构和计算相关性质.结果表明,[(U~Ⅱ)_2(L)]具有三重态基态,其电子组态为π~4σ~2δ~2;U(5f)原子轨道对高占据分子轨道有重要贡献;它的U—U键长为2.33?、Mayer键级为3.89和对应的伸缩振动频率为259 cm^(–1),被指认为U—U弱四重键.这一结论与QTAIM(quantum theory of atoms in molecule)的U—U键临界点处的电子/能量密度拓扑分析结果相一致.与不同氧化态铀同类物[(U^m)_2(L)]^(n+)(m=ⅡI,n=2;m=IV,n=4)比较显示,随着铀氧化态增大,U—U距离增长、键级变小、伸缩振动频率变小,金属铀电子自旋密度与常规预期值的差值(?SU)增大;结合分子轨道和QTAIM参数分析,发现金属氧化态可以调控配体和金属轨道能级匹配程度和改变金属-金属多重键.
基金Project supported by the National Natural Science Foundation of China （Nos. 20801017, 20973053, 21073051）, the Natural Science Foundation of Hebei Province （Nos. B2010000371, B2011205058）, the Education Department Foundation of Hebei Province （No.ZD2010126）.
文摘The intermolecular interactions in the dimers of m-nisoldipine polymorphism were studied by B3LYP calculations and quantum theory of ＂atoms in molecules＂ （QTAIM） studies. Four geometries of dimers were obtained： dimer I （a：dimer, O…H--N）, dimer II （b-dimer, O…H--N）, dimer III （b-dimer, n-stacking-c）, and dimer IV （b-dimer, n-stacking-p）. The interaction energies of the four dimers are along the sequence of II〉I〉III〉IV. The intermolecular distance of the interactions follows the order： I （O…H--N）〈II （O…H--N）, and III （n-stacking）〈 IV （n-stacking）. Both the O…H--N hydrogen-bonding and n-stacking interactions belong to weak non-covalent interactions. The O…H--N hydrogen-bonding interactions with more electrostatic characters are stronger than the n-stacking interactions. The strength of the weak interactions decreases in the order： I〉II〉III〉IV, and the electrostatic character decreases along the sequence： I〉II〉III〉IV.
