1,2-二硒-3，4-二硫方酸的从头计算

在RHF／STO－3G、STO－3G和3－21G（仅对ZE型）水平上，用abinitioSCF方法优化得到1，2－二硒－3，4－二硫方酸（3，4－二巯基－3－环丁烯－1，2－二硒酮）三种平面异构体的平衡构型，进一步用3－21G／／STO－3G（对ZZ和EE型）方法计算总能量，发现三种平面导构体中ZZ型是最稳定构象，ZE型次之，并与1，2－二硒方酸和3，4－二硫方酸从头算结果作了比较，用abinitio数值方法在STO－3G水平上计算了三种异构体的谐振动频率．     

多氯代菲分子结构和热力学性质的密度泛函理论研究

采用密度泛函理论方法在B3LYP/6-311G(d, p)水平上对527个多氯代菲分子的几何结构进行了全优化并计算得到它们的热力学性质(等容热容( )、熵(S$)、标准生成焓(ΔfH$)和标准生成Gibbs自由能(ΔfG$)), 研究了这些性质与取代的氯原子数目和位置的关系, 根据各异构体的相对标准生成Gibbs自由能(Δr,fG$)的大小, 得到它们的热力学稳定性顺序. 计算结果表明: 绝大多数多氯代菲分子具有非平面的几何构型, 在多氯代菲分子中存在三种类型的分子内弱相互作用(H…H、C—H…Cl和Cl…Cl相互作用), 随着分子中取代的氯原子数目的增加, 多氯代菲最稳定异构体的ΔfH$和ΔfG$开始时逐渐减小, 然后又快速增加. 具有相同数目氯原子的多氯代菲异构体的ΔfH$和ΔfG$与氯原子的取代位置有很大的关系. 多氯代菲异构体的相对热力学稳定性主要由分子内的离域π键和Cl…Cl核排斥作用的强弱决定.     

多溴二苯并呋喃的热力学性质和稳定性的密度泛函理论研究

在B3LYP/6-31G*水平上对二苯并呋喃和135个多溴二苯并呋喃系列化合物(PBDF)进行了全优化计算和振动分析, 得到各分子的总能量(E_T)、焓(H⁰)、熵(S⁰)、自由能(G⁰)和恒容热容(C_V⁰), 研究了这些参数与溴原子的取代数目及取代位置的关系. 溴原子置换在不同位置时, 使E_T, H⁰和G⁰数值增加大小次序为: 1(9)＞3(7)＞2(8)＞4(6), 即置换在1(9)位最不稳定; 两个溴原子处在同一苯环时, E_T, H⁰和G⁰数值也都增加, 增加的顺序为: 邻>>间＞对, 即相互处于邻位最不稳定. 而且有两个溴原子同时取代在1和9位时, 使H⁰和G⁰的数值的增加比取代在邻位、间位和对位时的增加值都大. 每增加1个溴原子, S⁰增大约40.1 J•mol^－1•K^－1, C_V⁰增大约16.3 J•mol^－1•K^－1. 同时, 设计等键反应, 计算了各异构体的标准生成热(H_f⁰)和标准生成自由能(G_f⁰). 根据异构体自由能的相对大小, 从理论上求得异构体的相对稳定性顺序, 各异构体组中的稳定性顺序与PCDF系列的稳定性顺序基本一致.     

全甲基化2,3,6—三—（O—2‘—羟丙基）—β—环糊精固定液热力学性质和分 …

将合成的全甲基化２，３，６－三（Ｏ－２‘－羟丙基）β－环糊精（ＰＭＨＰ－β－ＣＤ）固定液直接涂渍在弹性石英毛细管柱内壁，１４组对映异构体、６组芳香族益异构体化合物等在该柱上得到满意分离。通过测定以上化合物在该柱上的热力学参数：焓、熵、自由能及焓变差、熵变差、探讨了固定液对所测化合物的分子识别和色谱分离机理。结果表明，芳香族化全哦的△Ｓ－值在ＰＭＨＰ－β－ＣＤ高２０－３０Ｊ／ｍｏｌ．Ｋ，构型效应明显     

全甲基化2,3,6-三-(O-2’-羟丙基)β-环糊精固定液热力学性质和分离机理

将合成的全甲基化２，３，６－三（Ｏ－２’－羟丙基）β－环糊精（ＰＭＨＰ－β－ＣＤ）固定液直接涂渍 在弹性石英毛细管柱内壁，１４组对映异构体、６组芳香族位置异构体化合物等在该柱上得到 满意分离。通过测定以上化合物在该柱上的热力学参数：焓、熵、自由能及焓变差、熵变差，探 讨了固定液对所测化合物的分子识别和色谱分离机理。结果表明，芳香族化合物的－△Ｓ值在 ＰＭＨＰ－β－ＣＤ柱上比 ＴＢ－β－ＣＤ高２０～３０ Ｊ／ｍｏｌ·Ｋ，构型效应明显，极性选择性也比后者高。     

1,2-二硒方酸的从头计算

在ＲＨＦ／ＳＴＯ－３Ｇ和ＳＴＯ－３Ｇ＊水平上用ａｂｉｎｉｔｉｏＳＣＦ方法优化得到１，２－二硒方酸（３，４－二羟基－３－环丁烯－１，２－二硒酮）三种平面异构体的平衡几何构型，发现三种平面异构体中ＺＺ型是能量最低构象。用ａｂｉｎｉｔｉｏ数值方法在ＲＨＦ／ＳＴＯ－３Ｇ＊水平上计算了三种平面异构体的谐振动频率。     

1,3-二甲氧甲酰-4,6-二氰基噻吩并[3,4-c]噻吩的合成和密度泛函理论研究

设计采用新颖的Pummerer-氰化路线和用亚硫酰氯作S-转移试剂的路线合成了第一例全部连吸电子基的噻吩并[3,4-c]噻吩. 用¹H NMR, ¹³C NMR, FTIR, 元素分析和X射线衍射分析进行了表征. 用B3LYP/6-31G^*及B3LYP/6- 311＋＋G^**方法全优化计算了1,3-二甲氧甲酰-4,6-二氰基吩并[3,4-c]噻吩分子, 得到几何构型、总能量、标准熵、标准焓和标准自由能, 计算构型与X射线衍射测定结果非常吻合. 并用电荷分布讨论了有关非经典噻吩并[3,4-c]噻吩体系的稳定性, 计算结果能很好地解释有关实验现象.     

几个分子和负离子的QCI势能曲线

用ＱＣＩＳＤ（Ｔ）／６３１１＋Ｇ（３ｄｆ，２ｐ）（简称ＱＣＩ）计算了ＢＨ－（２Π），ＢＦ－（２Π），ＢＨ（１∑），ＢｅＨ－（１∑），ＢｅＦ－（１∑）和ＢＦ（１∑）的较完整的势能曲线，探讨了这些体系的稳定性和解离过程．同时用Ｍｏｒｓｅ函数和ＥＲ函数拟合得到势能曲线，用拟合结果计算谐性频率和非谐性频率，并与已有的实验数据（ＢＨ和ＢＦ分子）进行比较，由此考察了ＱＣＩ理论方法在远离平衡构型时的可靠性．对于因单参考态近似导致的反常势能曲线进行了ＣＡＳＳＣＦ计算．还比较了ＱＣＩ和Ｇ２理论中标准的ＭＰ２（ｆｕｌ）／６３１平衡几何构型及其对ＱＣＩ总能量的影响．     

异构现象与最大硬度原理

利用原子-键电负性均衡方法计算了700多个异构体的硬度, 通过与标准生成焓所确定的相对稳定性比较后发现, 多数异构体并不遵守最大硬度原理.     

氟比洛芬构象异构体的理论计算

用Hypercbem软件中构象搜寻模块,对氟比洛芬进行构象搜索,寻找分子低能构象．用B3LYP／6-31G（d）法优化计算22个低能构象,PCM溶剂模型用于水相计算,获得低能构象的优化几何结构、分子总能量和标准吉布斯自由能．结果表明,在气相和水相时,Z-型构象异构体稳定性最高．     

Theoretical Studies on the Molecular Structures and Thermodynamic Properties of Polychlorinated Fluorenes

Geometric structures of 135 polychlorinated fluorene (PCFR) molecules were optimized using density functional theory (DFT) at the B3LYP/6-311G** level and their thermodynamic properties in the ideal gas state were calculated. The relations of these thermodynamic properties with the number and position of chlorine atoms were also explored, from which the relative stability of PCFR congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation (Δr,fGθ). The results show that the geometric configuration of PCFR isomers is determined by the position of chlorine atoms. There exist two types of intramolecular weak interactions, i.e., C-H···Cl and Cl···Cl interactions in PCFR molecules. The change of ΔfHθ and ΔfGθ of most stable PCFR isomers with increasing the number of chlorine atoms is different from that in most unstable PCFR congeners. The values of ΔfHθ and ΔfGθ for PCFR isomers with the same number of chlorine atoms strongly depend on the position of chlorine atoms and the relative stability of PCFR congeners is mainly determined by intramolecular delocalized π bond and Cl···Cl nuclear repulsive interaction.     

Theoretical Studies on the Molecular Structures and Thermodynamic Properties of Polychlorinated Fluoranthenes

DFT-B3LYP/6-311G** method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene(PCFRT) congeners and calculate their thermo-dynamic properties in the ideal gas state,such as heat capacity at constant volume(Cv),entropy(S),standard enthalpy of formation(ΔfH) and standard Gibbs free energy of formation(ΔfG).The relations of Cv,S,ΔfH and ΔfG with the number and position of chlorine atoms have also been explored,from which the relative stability of PCFRT congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation(Δr,fG).It was found that some of the PCFRT isomers are in a nonplanar configuration and there are intramolecular Cl…Cl weak interactions in some of the isomers.With increasing the number of chlorine atoms,the values of ΔfH and ΔfG of the most stable PCFRT isomers decrease initially and then increase.The values of ΔfH and ΔfG of PCFRT congeners with the same number of chlorine atoms show a strong dependence on the positions of chlorine atoms.The relative thermodynamic stability of PCFRT isomers is determined mainly by intramolecular adjacent Cl…Cl nuclear repulsive interaction between Cl atoms at two different six-membered rings.Most PCFRT congeners are easier to form thermodynamically than their parent compound.     

Theoretical Studies on the Molecular Structures and Thermodynamic Properties of Polychlorinated Acenaphthylenes

Geometric structures of 135 polychlorinated acenaphthylene (PCAC) molecules were optimized using density functional theory (DFT) at the B3LYP/6-311G** level and some thermodynamic properties of them in the ideal gas state were calculated. The relations of these thermodynamic properties with the number and position of chlorine atoms were also explored, from which the relative stability of PCAC congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation (△r,fGθ). The results show that all PCAC isomers have planar geometric configuration. There exists intramolecular Cl···Cl weak interaction in some PCAC molecules. The change of △fHθ and fGθ of most stable PCAC isomers with increasing the number of chlorine atoms is different from that in the least stable PCAC congeners. The values of fHθ and fGθ for PCAC isomers with the same number of chlorine atoms show a strong dependence on the position of chlorine atoms and the relative stability of PCAC congeners has close relation with the intramolecular Cl···Cl nuclear repulsive interaction.     

7-硫代鸟嘌呤互变异构体的密度泛函理论计算

在密度泛函B3LYP/6-311G^**水平下,对14种气相和水相中可能存在的7-硫代鸟嘌呤异构体进行了几何构型全自由度优化,并计算出它们的总能量、焓、熵、吉布斯自由能.Onsager反应场溶剂模型用于水相的计算.计算结果表明,7-硫代鸟嘌呤在气相中和水相中主要以硫酮形式存在.在气相中,硫酮-N(6)(H)要比硫酮-N(4)(H)更稳定,而在水相中,则硫酮-N(4)(H)要比硫酮-N(6)(H)更稳定.计算结果同已有实验结果一致.7-硫代鸟嘌呤互变异构的熵效应小,对互变异构平衡没有显著的影响,而焓变对互变异构产生了主要的影响.较详细地讨论了水溶剂化作用对异构体的能量、几何结构、电荷分布和偶极矩的影响.溶剂化自由能与异构体的偶极矩存在相关性.     

6-巯基嘌呤互变异构体的密度泛函理论计算

在密度泛函B3LYP/6-311G水平下,对8种气相和水相中可能存在的6-巯基嘌呤异构体进行了几何构型的全自由度优化,并计算出它们的总能量、焓、熵、吉布斯自由能．Onsager反应场溶剂模型用于水相的计算．计算结果表明,6-巯基嘌呤在气相和水相中主要以硫酮形式存在．在气相中,硫酮．N(7)(H)要比硫酮-N(9)(H)更稳定,而在水相中,则硫酮-N(9)(H)要比硫酮-N(7)(H)更稳定．计算结果同已有实验结果一致．6-巯基嘌呤的熵效应小,对互变异构平衡几乎没有显著的影响,而焓变对互变异构产生了主要的影响．较详细地讨论了水溶剂化作用对异构体的能量、几何结构、电荷分布和偶极矩的影响,溶剂化吉布斯自由能与异构体的气相偶极矩存在相关性．     

Theoretical Study on the Electronic Structures of Small TinNm （n ＋ m = 5, 6） Clusters

45 isomers of TinNm （n ＋ m = 5, 6） clusters, including linear, some planar and some stero configurations, have been predicted by density functional theory method. For five-atom clusters Ti3N2 and Ti2N3, the most stable structures are trigonal bipyramid in D3h symmetry, and for TiaN cluster, the isomer with one nitrogen atom occupying the center of quasi-tetrahedron is the most stable. In the isomers of Ti4N2 and Ti3N3, the planar networks are more stable, but for Ti2N4, the six-membered ring configuration is the most favorable. Most linear structures can form weak-strong bonds alternately with higher energy. As regards to planar structures, the more Ti-N bonds are formed, the more stable they will be; for stero closed polyhedral isomers, their energies are lower.     

黄嘌呤及其互变异构体的密度泛函理论研究

嘌呤碱及其衍生物在生物系统中起重要作用。对人具有兴奋和利尿作用的茶碱和咖啡碱就是黄嘌呤的甲基衍生物。黄嘌呤存在多种互变异构体，从理论计算的角度研究这些互变异构体的几何结构、电子结构及相对稳定性，进一步研究溶剂对其结构和性质的影响是有意义旧。密度泛函理论方法既考虑了电子相关，又较其它CI（组态相互作用）或MPn（n级微扰）方法节省机时。其计算结果较好，被广泛应用于研究各种化合物。本文采用密度泛函B3LYP／6—311G方法对14种黄嘌呤可能的互变异构体（见图1），分别在气相和水相中进行几何构型全自由度优化和能量计算，讨论了异构体的相对稳定性，水的溶剂化作用对异构体的能量、几何构型、电荷分布和偶极矩的影响，探讨了溶剂极性对异构体的能量和偶极矩的影响。     

Geometry,electronic structure and energy barriers of all possible isomers of Fe<Subscript>2</Subscript>C<Subscript>3</Subscript> nanoparticle

The search for stable structures of neutral Fe₂C₃ particle was based on the geometry optimization of the known FeC₃ and Fe₂C₂ isomers with the Fe and C atoms approaching from various directions. The geometry optimization of more than 2,000 initial structures was carried out using the DFT based DMol³ method and converged to 41 stable configurations. The structures containing C₃ triangle and the cyclic planar isomer with transannular bonds are found to have the lowest binding energies. The effective charges and total spin densities on the atoms were calculated using integral scheme incorporated in DVM and Hirshfeld procedure of DMol³. The relations between geometrical structures and spin moments ordering are discussed. For the evaluation of potential barriers the geometry optimization of all Fe₂C₃ configurations was performed with a thermal occupation, corresponding to the various values of the excitation energy.     

Ab initio Study on the Molecular Geometry,Electronic Structure and Thermodynamic Properties of Benzotrifuroxan(BTF)

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