木犀草素与胞嘧啶相互作用的理论研究

采用密度泛函理论中的B3LYP方法,在6-31＋G＊基组水平上对木犀草素、胞嘧啶、木犀草素-胞嘧啶复合物进行结构优化和振动频率分析,得到了12种稳定复合物.并应用分子中的原子理论（AIM）分析、自然键轨道（NBO）理论分析得到复合物氢键性质和特征.通过基组重叠误差（BSSE）校正后的相互作用能、成键临界点电荷密度、二阶...     

Density Functional Theory Study on Hydrogen Bonding Interaction of Catechin-(H2O)n

Density functional theory B3LYP method with 6‐31G* basis set has been used to optimize the geometries of the catechin, water and catechin‐(H₂O)_n complexes. The vibrational frequencies have been studied at the same level to analyze these complexes. Six and eleven stable structures for the catechin‐H₂O and catechin‐(H₂O)₂ have been found, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are from ?13.27 to ?83.56 kJ/mol. All calculations also indicate that there are strong hydrogen‐bonding interactions in catechin‐water complexes. The strong hydrogen‐bonding contributes to the interaction energies dominantly. The O–H stretching motions in all the complexes are red‐shifted relative to that of the monomer.     

Density Functional Theory Study on Interaction between Catechin and Thymine

The interacting patterns and mechanism of the catechin and thymine have been investigated with the density functional theory Becke's three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional (B3LYP) method by 6-31+G*basis set. Thirteen stable structures for the catechin-thymine complexes have been found which form two hydrogen bonds at least. The vibrational frequencies are also studied at the same level to analyze these complexes. The results indicated that catechin interactedwith thymine by three different hydrogen bonds as N-H…O、C-H…O、O-H…O and the complexes are mainly stabilized by the hydrogen bonding interactions. Theories of atoms in molecules and natural bond orbital have been adopted to investigate the hydrogen bondsinvolved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error, which are from -18.15 kJ/mol to -32.99 kJ/mol. The results showed that the hydrogen bonding contribute to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red-shifted relative to that of the monomer, which is in agreement with experimental results.     

Density Functional Theory Study of the Interaction between Guanine and Catechin

The interacting patterns and mechanism of the catechin and guanine have been investigated with the density functional theory B3LYP method by 6‐31G* basis set. Fourteen stable structures for the catechin‐guanine complexes have been found which form two hydrogen bonds at least. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. At the same time, the number and strength of hydrogen bond play a co‐determinant parts in the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error (BSSE), ranging from ?38.86 to ?14.56 kJ/mol. The results showed that the hydrogen bonding contributes to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red‐shifted relative to that of the monomer, which is in agreement with experimental results.     

1,2,4-三氮杂苯-(H2O)n复合物氢键相互作用的密度泛函理论研究

用密度泛函理论方法在B3LYP/6-31++G**水平上对1,2,4-三氮杂苯-(H₂O)_n (n＝1, 2, 3)氢键复合物的基态进行了结构优化和能量计算, 结果表明复合物之间存在较强的氢键作用, 所有稳定复合物结构中形成一个N…H—O氢键并终止于弱O…H—C氢键的氢键水链的构型最稳定. 同时, 用含时密度泛函理论方法(TD-DFT)在TD-B3LYP/6-31++G**水平上计算了1,2,4-三氮杂苯单体及其氢键复合物的单重态第一¹(n, π^*)垂直激发能.     

单嘧磺隆除草剂的晶体构象-活性构象转换的密度泛函理论研究

应用密度泛函理论在B3LYP/6-31G(d)水平上对新型除草剂单嘧磺隆绕脲桥部分两个C—N键的内旋转势能面进行计算, 然后对势能面上的驻点进行构型优化和过渡态搜索, 得到单嘧磺隆4种稳定构象和构象转换过程所涉及的8个过渡态结构. 研究结果表明, 单嘧磺隆晶体构象-活性构象转换过程中涉及4种稳定构象和8条转换途径, 脲桥部分NH基团与嘧啶环上N原子所形成的分子内氢键对于构象的稳定性及转换过程起着十分重要的作用. 应用极化连续介质溶剂模型(PCM)在B3LYP/6-31＋＋G(d, p)水平下进行溶剂化效应计算, 结果表明单嘧磺隆从晶体构象转换成活性构象主要是在水相中进行的.     

1,2,4-三氮杂苯-(H2O)n复合物氢键相互作用的密度泛函理论研究

用密度泛函理论方法在B3LYP／6—31 G**水平上对1，2，4-三氮杂苯-(H2O)n(n=1，2，3)氢键复合物的基态进行了结构优化和能量计算，结果表明复合物之间存在较强的氢键作用，所有稳定复合物结构中形成一个N…H--O氢键并终止于弱O…H—C氢键的氢键水链的构型最稳定．同时，用含时密度泛函理论方法(TD—DPT)在TD—B3LYP／6—31 G**水平上计算了1,2，4-三氮杂苯单体及其氢键复合物的单重态第-1(n，π*)垂直激发能．     

Quantum Study on the Hydrogen Bonding Interaction of Luteolin-（CH_3OH）_n

The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-(CH3OH)n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six stable luteolin-(CH3OH)2 complexes and four stable luteolin-(CH3OH)3 complexes have been obtained.The theories of atoms in molecules(AIM) and natural bond orbital(NBO) have been used to analyze the hydrogen bonds of these compounds,and their interaction energies corrected by basis set superposition error are between-8.046 and-76.124 kJ/mol.The calculation results indicate strong hydrogen bonding interactions in the luteolin-(CH3OH)n complexes.Then the nuclear magnetic resonance(NMR) and electronic absorption spectrum of luteolin have been calculated,and the results are in agreement with the experimental data.     

4-羟甲基吡啶－水红移氢键的密度泛函理论研究

使用密度泛函理论B3LYP方法和6-311++G**基函数对4-羟甲基吡啶与水形成的1:1和1:2（摩尔比）氢键复合物进行了理论计算研究,分别得到稳定的4-羟甲基吡啶－H₂O和4-羟甲基吡啶－(H₂O)₂氢键复合物3个和8个。经基组重叠误差和零点振动能校正后,最稳定的1:1和1:2氢键复合物的相互作用能分别为-20.536和-44.246 kJ/mol。振动分析显示O-H···N(O)氢键的形成使复合物中O-H键对称伸缩振动频率红移(减小)。自然键轨道分析表明,4-羟甲基吡啶与水形成最稳定的1:1和1:2氢键复合物时,分子间电荷转移分别为0.02642 e 和0.03813 e 。含时密度泛函理论TD-B3LYP/ 6-311++G**计算显示,相对于4-羟甲基吡啶单体分子,氢键H-OH···N和H-OH···OH的形成分别使最大吸收光谱波长兰移8~16纳米和红移4~11纳米。     

用GGA密度泛函及其长程、色散校正方法计算各类氢键的结合能

应用广义梯度近似(GGA) (PW91和PBE)、含动能密度的广义梯度近似(meta-GGA) (M06-L)、杂化泛函(hyper-GGA)(M06-2X、X3LYP和B3LYP)及其长程校正泛函LC-DFT(CAM-B3LYP、LC-ωPBE和ωB97X)和色散校正密度泛函(DFT-D)(ωB97X-D和B97-D),用多种基函数对15种不同强度的传统氢键和非传统氢键体系的结合能进行了系统的计算与分析.并与高精度的CCSD(T)/aug-cc-pVQZ结果比较发现:在上述各类泛函中,对于氢键结合能的计算M06-2X和ωB97X-D泛函较为精确与可靠,且没有必要使用过大的基函数,6-311++G(2d,2p)或aug-cc-pVDZ水平的基组就已足够,各类泛函所计算结合能的基组重叠误差(BSSE)均较小,除ωB97X和ωB97X-D外,其它9种泛函不经BSSE校正也能得到同样甚至更准确的结果.     

新型异三聚体超分子的密度泛函计算及其晶体结构、热性能研究

运用密度泛函B3LYP方法,在6-31G^*水平上设计优化了丁二酮肟与苯甲酸通过四重氢键构筑的异三聚体超分子、此异三聚体的总能量比三个单体总能量之和低144．0816kJ／mol,四重氢键的平均键能约为36．0204kJ／mol,属中高强度;298．15K时吉布斯自由能变化△GT=-41．70kJ／mol,显示形成三聚体的反应可自发进行．在此设想指导下,实验合成出相关异三聚体,并得到了晶体结构,与预测的结构极为相似．热性能分析显示,此三聚体不是三个单体的简单叠加,而是一个不同于其单体的全新化合物．理论计算数据与实验结果的一致性,证明了理论计算的预见性．     

碳氟键均裂解离能的密度泛函理论研究

运用6种密度泛函方法(B3LYP, B3P86, B3PW91, PBE1PBE, MPW1B95, MPW1K)对15个含氟有机化合物的碳氟键均裂解离能进行理论计算, 得到的理论值与实验值比较, 发现B3P86方法用于碳氟键均裂解离能的计算相对可靠. 使用验证后的理论方法对含氟杂环有机化合物和卤氟烃中的碳氟键均裂解离能进行了预测和分析, 并进一步讨论了α-取代基效应以及Hammett型取代基效应对碳氟键均裂解离能的影响.     

过渡金属混合簇Nb2Rh2的密度泛函研究

采用密度泛函方法(DFT)研究了过渡金属混合簇Nb_mRh_n (m, n≤2) 的结构、稳定性规律及它们的成键情况. 结果表明, Nb—Nb键较强, Rh—Rh键较弱, 而Nb—Rh键的强度则介于两者之间. 在Nb₂Rh₂直线和折线构型中, 金属键有强弱交替的现象. Nb₂Rh₂的各种构型在自旋多重度较小时稳定.     

Density Functional Calculations on a Double Hydrogen-bonded Dimer

Density functional theory (DFT) calculations on a double hydrogen-bonded dimer of o-hydroxybenzoic acid were carried out at the B3LYP/6-31G^* level. The optimized geometry of the dimer closely resembles that of the crystal. The calculated results show that the total energy of the dimer is much lower than the sum energies of the two monomers, and the average strength of the double hydrogen bonds is about 38.37 kJ/mol. In order to probe the origin of the interactions in the dimer, natural bond orbital analyses were performed. The thermodynamic properties of the title compound at different temperatures have also been calculated on the basis of vibrational analyses and ΔGT, the change of Gibbs free energy for the aggregation from monomer to the dimmer, is 26.47 kJ/mol at 298.15 K and 0.1MPa, implying the spontaneous process of forming the dimer. The correlation graphics of Sm^0 Hm^0 and temperatures is depicted.     

烃类化合物碳氢键解离焓的密度泛函理论研究

通过比较10种密度泛函方法对烃类化合物碳氢键解离焓的计算精度, 发现新型密度泛函BMK方法具有最高的计算精度. 利用该方法计算了包含饱和链烃,、不饱和链烃、脂环烃和芳香烃在内的172个烃类化合物的碳氢键解离焓,计算均方根误差仅为7.95 kJ•mol^－1, 线性拟合常数为0.985. 通过自然键轨道法分析发现, 烃类物质的碳氢键解离焓与母体的碳氢键杂化轨道成分p%, 自由基奇电子轨道杂化成分p%及自由基的自旋密度三个参数之间存在较好的定量关系. 此外, 饱和链烷烃及不饱和链烃的碳氢键解离焓与碳氢键键长之间也存在较好的线性关系.     

Theoretical Investigation on Interaction between Guanine and Luteolin

The interacting patterns of the luteolin and guanine have been investigated by using the density functional theory B3LYP method with 6-31＋G＊ basis set. Eighteen stable structures for the luteolin-guanine complexes have been found respectively. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. Meanwhile, both the number and strength of hydrogen bond play important roles in determining the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules and natural bond orbital have also been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes which were corrected by basis set superposition error are 6.04-56.94 kJ/mol. The calculation results indicate that there are strong hydrogen bonding interactions in the luteolin-guanine complexes. We compared the interaction between luteolin and four bases of DNA, and found luteolin-thymine was the strongest and luteolin-adenine was the weakest. The interaction between luteolin and DNA bases are all stronger than luteolin-water.     

肾上腺素与胞嘧啶相互作用的密度泛函理论研究

采用密度泛函理论（DFT）B3LYP方法和6-311＋G（d,p）基组对肾上腺素-胞嘧啶复合物进行结构优化和频率计算,得到15种稳定的复合物.研究发现,所有的复合物进行基组重叠误差（BSSE）校正后的相互作用能为-11.43^-48.96kJ/mol,符合氢键能量范围,相互作用能主要由氢键所贡献.结构和振动频率分析显示,氢键的形成使相应O（N）—H键的键长变长,对称伸缩振动频率减小,说明复合物中形成的氢键都是正常的红移型氢键.应用自然键轨道（NBO）理论和分子中的原子（AIM）理论对15种复合物的氢键性质和特征进行分析,发现氢键对于复合物的稳定性起着重要作用,当复合物形成2个或更多的氢键时,氢键的数目、类型及强度共同决定着复合物的稳定性,复合物基本符合三氢键〉二氢键〉单氢键的稳定顺序,三氢键复合物4是最稳定的,复合物3存在单氢键O—H…O,比部分二氢键复合物要稳定.     

CuCl与SiO_2-TiO_2载体相互作用的密度泛函理论研究

以SiO2簇模型为基体,通过Ti原子取代建立Ti中心原子上连接0个或1个OH基团的典型SiO2-TiO2复合氧化物模型来模拟处于体相中和表面上的四配位Ti(IV)中心.采用广义梯度近似的密度泛函理论(DFT-GGA)研究了CuCl与SiO2-TiO2载体的相互作用.计算结果表明,在SiO2基体中嵌入Ti(IV)离子可以大大加强CuCl与氧化物载体之间的相互作用,使CuCl/SiO2-TiO2催化剂的结构更稳定.分子前线轨道表明Cu(I)作为催化剂的活性中心贡献了HOMO轨道,容易失去电子;Ti(IV)中心原子贡献LUMO轨道,容易得到电子,计算结果与实验事实相一致.     

Theoretical Study of the N-NO2 Bond Dissociation Energies for Energetic Materials with Density Functional Theory

The N-NO2 bond dissociation energies （BDEs） for 7 energetic materials were computed by means of accurate density functional theory （B3LYP, B3PW91 and B3P86） with 6-31G＊＊ and 6-311G＊＊ basis sets. By comparing the computed energies and experimental results, we find that the B3P86/6-311G＊＊ method can give good results of BDE, which has the mean absolute deviation of 1.30kcal/mol. In addition, substituent effects were also taken into account. It is noted that the Hammett constants of substituent groups are related to the BDEs of the N-NO2 bond and the bond dissociation energies of the energetic materials studied decrease when increasing the number of NO2 group.     

Generalization of the Hylleraas functional for calculating BSSE-free intermolecular interactions: further considerations

The generalized Hylleraas functional necessary for calculating BSSE-free intermolecular interactions is presented for the case when exclusion of BSSE results in non-Hermitian operators and the intra- and intermolecular interactions are treated in different orders of perturbations.