DFT结合QTAIM方法对(CH)_n(CBO)_(6-n)(n=0～6)结构和芳香性的研究

在B3LYP／6-311＋G（d）计算水平上对（CH）n（CBO）6-n（n=0-6）分子的结构进行了全优化，在同一计算水平上采用规范无关原子轨道（GIAO）方法计算了此类化合物的核独立化学位移值（NICS），用以评价这些分子的芳香性．研究结果表明：（CH）n（CBO）6-n（n=0—6）具有芳香性，但芳香性比苯分子略弱，并且芳香性随着CH基团陆续被CBO基团取代而减弱．QTAIM分析进一步确认了这些分子的芳香性，并发现NICS（0）以及△NICS均同Hb存在良好的线性关系．此外，同（CH）a（BCO）6-n（n=0-6）化合物相比，（CH）n（CBO）6-n（n=0-6）分子不仅具有更高的热力学稳旬洼，而且还具有更强的芳香性．

Optimization, Spectroscopic(FT-IR, Excited States, UV/Vis) Studies, FMO, ELF, LOL, QTAIM and NBO Analyses and Electronic Properties of Two New Pyrimidine Derivatives

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.

Computational Study of the Alkylation Reaction of the Nitrogen Mustard Mechlorethamine Using NBO Model and the QTAIM Theory

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.

Theoretical study on the structural, mechanical, electronic properties and QTAIM of CrB_4 as a hard material

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.

采用12种密度泛函理论方法表征三种三价铀复合物（英文）

比较了BP86、PBE、B3LYP、B3PW91、BHand HLYP、PBE0、X3LYP、CAM-B3LYP、TPSS、M06L、M06和M06-2X等12种采用了广义梯度近似(GGA、hybrid GGA、meta-GGA和hybrid meta-GGA)的密度泛函理论(DFT)方法在三个三价铀复合物表征中的应用.研究模型采用铀复合物催化CO2和CS2官能团化反应中的三个中间体(Tp*)2U-η1-CH2Ph(Cpd2),(Tp*)2U-κ2-O2CCH2Ph(Cpd3)和(Tp*)2U-κ2-S2CCH2Ph(Cpd4).研究发现,B3LYP和B3PW91在几何结构和电子结构方面优于其它方法.基于分子轨道理论的MP2方法在Cpd2和Cpd3的表征中给出与DFT方法相近的结果,而在Cpd4的表征中表现出较大的差异.这可能是由于同样是单参考态方法的MP2捕捉到了与DFT方法不同的电子结构.同时,通过对比分别采用小核赝势(5f-in-valence)和大核赝势(5f-in-core)基组处理铀原子的计算结果,发现对测试的模型体系,两种处理方法可获得相近的热力学能量.与以往主要关注高价态锕系复合物的处理方法的评估工作不同,本项工作适应逐渐增加的对低价态锕系分子体系的研究的需求,对12种常用的密度泛函理论方法在低价态锕系复合物研究中的应用进行了评估,期望为处理类似体系的研究工作提供参考.

对乙酰氨基酚-水复合物中氢键作用的理论研究

为了解对乙酰氨基酚(AP)在水溶液中的构象,在MP2/6-311++G(d,p)水平上研究了AP与水分子通过不同种氢键作用形成的6种AP-H2O复合物.首先分析这些复合物的几何结构、能量和振动频率,然后运用分子中原子的量子理论(QTAIM)、自然键轨道理论(NBO)和定域分子轨道-能量分解分析(LMO-EDA)等理论和方法对AP-H_2O复合物中的氢键相互作用进行定性和定量分析.研究结果表明:(1)AP分子中的—CH基团与羰基氧原子之间形成的C8H8A···O2A分子内氢键在多数AP-H_2O复合物中被保留下来;(2)AW1和AW6中的分子间氢键强于其他氢键;(3)AP的羰基氧原子是最有可能与H_2O分子形成氢键的位点,第2个最有可能与H_2O分子形成氢键的位点是AP的酚羟基,前者中H_2O是质子供体,而后者中H_2O则是质子受体;(4)AP-H_2O的形成过程中,氢键作用与结构畸变都会在一定程度上决定AP-H_2O复合物的相对稳定性,但前者的作用更大.

六聚吡咯大环与铀/超铀酰基离子相互作用:成键、热力学和光谱性质

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。

双层三明治四聚吡咯铀配合物的结构设计和稳定性理论计算

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.

三明治型四聚吡咯低价铀配合物结构、成键和氧化还原性质的相对论密度泛函理论研究

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。

小镍团簇Ni_n(n=2～6)电子结构和拓扑分析

在UBP86/TZVP水平上计算了小镍团簇(Nin,n=2～6)的稳定基态结构并用自然键轨道(NBO)和分子中的原子量子理论(QTAIM)分析了这些团簇的电子结构。计算结果表明,Ni团簇基态结构具有较高自旋多重度。QTAIM分析表明镍团簇中Ni-Ni键均为金属键。除Ni2团簇中Ni-Ni键为纯粹的σ键外,其他团簇中Ni-Ni键具有部分π键特征。提出了采用团簇的原子平均离域化指数(δ)来表示团簇的相对稳定性,平均离域化指数与团簇的平均结合能具有较好线性关系。

A Theoretical Study of Binary and Ternary Hydride-Bonded Complexes N(Beh₂)...X with N = 1 or 2 and X = K⁺or Ca⁺²

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.

Conformational and Bonding Analysis of C₂H₄²⁺

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.

环戊二烯基锕系配合物结构和还原性质的密度泛函理论研究

深入理解锕系有机金属配合物的结构和化学反应性质对锕系配位化学的发展至关重要。运用密度泛函理论系统计算了环戊二烯基配位铀化合物,[Cp3UmX]n(X=F, Cl, Br, I;m=Ⅲ, n=-1;m=Ⅳ, n=0)和[Cp3UmX]n(X=Vacant;m=Ⅲ, n=0;m=Ⅳ, n=+1)。异构体优化表明四价和三价铀配合物分别对应三重态和四重态基态。与四价铀配合物的结构参数相比较,三价的U-C、U-Cpcent和U-X距离更长;这与UⅢ离子半径长于UⅣ的相一致。基于电子密度的原子在分子中量子理论计算指认U-X间为配位单键本质。电子自旋密度分析揭示单电子反应为金属铀主导、Cp配体参与的还原机制。研究发现,随着配体X从F、Cl、Br、I变化到Vacant(空置未配位),配合物的还原电势(E0)逐渐变小,并进一步建立了E0与U-Cp作用强度之间的正相关规律性。同时考虑溶剂化和自旋-轨道耦合效应时,计算的还原电势在报道的实验值范围内。另外,变换金属并计算了[Cp3Anm]n(An=U, Np, Pu;m=Ⅲ, n=0;m=Ⅳ, n=+1)结构和还原性质,得到的还原电势值随U、Np、Pu依次增大,与实验测得的An4+/An3+离子E0值趋相一致。

Ni原子活化氨分子理论研究

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.

金红石纳米团簇与铀酰离子界面作用理论研究

为探索无机氧化物矿物质与锕系物种的界面作用和成键本质,设计优化了实验已知稳定的金红石(110)表面纳米团簇(SNCs).计算表明中性和弱酸性溶液中的sol模型比pH较小情况下的sat模型吸附更有利,与实验观察到的提高溶液pH导致铀酰吸附速率降低的结果相一致.能量分解表明,界面吸附主要以轨道吸引作用为主,并伴有少量空间效应贡献.电子密度拓扑分析与吸附能数据给出配合物中相同的U—Osurf键强顺序,而红外光谱则显示出相反的键强顺序.电子结构分析表明,所有水合铀酰-SNCs复合物均具有相似分子轨道性质和能量排列顺序,但是HOMO-LUMO能隙和轨道能量有所差异.因此,solbt模式与水合铀酰离子成键作用最强,且吸附作用也最强.

二价双核铀聚吡咯配合物结构设计和铀-铀多重键的理论研究

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.

金属硫化物富勒烯Sc_2S@C_(90)的结构与性质

Sc2S@C90存在的信号已经被质谱检测到,但其结构还没有得到表征.为了研究Sc2S@C90的结构和性质,通过密度泛函理论计算方法对Sc2S@C90的异构体进行了系统的筛选.计算结果表明,能量最低的两个异构体分别为Sc2S@C90:99913和Sc2S@C90:99915.对Sc2S@C90在0到4000 K温度下的相对浓度进行了评估,结果显示,Sc2S@C90:99913和Sc2S@C90:99915可以在高温下共存.分析研究了Sc2S@C90的内嵌团簇与碳笼间的键连关系和相互作用特性.这些研究可为Sc2S@C90的结构确定提供指导.

Theoretical Studies on the Hydrogen-bonding and π-Stacking Interactions in the m-Nisoldipine Polymorphism Dimers

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.

Theoretical Study on the Hydrogen Bonding Interactions in Complexes of 5-Hydroxytryptamine with Water

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.

Local Energy Dissipation/Transition in Field Effect Molecular Nanoelectronic Systems:a Quantum Mechanical Methodology

Electronic and vibrational intra-molecular thermoelectric-like ?gures of merit(ZT_γ~M) are introduced for single molecule nanoelectronic system, using quantum theory of atoms in molecule. These ?gures of merit are used to describe intra-molecular or local energy dissipation/transition(as in Joule-like, Peltier-like, and Thomson-like effects) in?eld effect molecular devices. The ZT_γ~M?gures of merit are computed for two proposed molecular devices. Analysis of the results shows that ZT_γ~Mdepends almost non-linearly on the electric ?eld(EF) strength. Also, the intra-molecular Joule-like heating plays a dominant role in the local energy dissipation, and intra-molecular Thomson-like heating is generally larger than the intra-molecular Peltier-like heating. Introduction of ZT_γ~Mcan be applied to extend the analysis of thermoelectric heating down to molecular and intra-molecular levels, and thus can be used to predict characteristics and performance of any candidate multi-terminal or multi-pole molecular systems prior to their application in real nanoelectronic circuits.