7-羟基喹啉-(H2O)n(n=1,2)复合物氢键相互作用的密度泛函理论研究

许多生理过程都通过分子间相互作用来实现。氢键则是最基本的化学作用力之一。具有碱性和酸性双官能团的芳香族化合物能与水作用形成氢键网络,对于实现生物体系的物质转移（质子转移、离子转移）起着十分重要的作用。在非水溶剂中,通过氢键发生质子转移反应动力学实验特征也己进行了广泛的研究。本文用密度泛函B3LYP方法在6-311G^＊基组水平上对7-羟基喹啉-水复合物相互作用进行了研究,从成键特征及氢键复合物的稳定关系方面进行了理论计算。     

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...     

吡咯-HCN体系在气相及溶液中相互作用的理论研究

用量子化学B3LYP方法在6-311G(d, p)水平上优化了吡咯-HCN氢键复合物，通过振动频率分析确定了两个吡咯-HCN体系稳定构型.为了得到更加精确的氢键作用能，采用相关一致基组aug-cc-pVDZ以及Boys 和Bernardi的CP(counterpoise)校正方法消除基组重叠误差后得到C－H…π和N－H…N型复合物的氢键相互作用能.为了确定B3LYP方法计算的相互作用能的可靠性，在MP2/aug-cc-pVDZ水平计算了复合物的氢键相互作用能，结果分别为－25.10和－19.30 kJ·mol－1.采用自然键轨道(NBO)分析考察了吡咯与HCN分子间轨道相互作用.以自洽场理论(SCRF)中的Onsager模型研究了不同极性溶剂对吡咯-氰化氢体系N－H…N型氢键几何构型，频率位移，电荷分布以及相对能量的影响.研究发现，当溶液的介电常数在1.5～30.0范围时，溶液作用十分显著，而当介电常数超过30.0以后，溶液作用已经达到了极限.     

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.     

氢键链质子接受能力对质子转移反应影响的理论研究

采用密度泛函B3LYP方法,6-311+g(d,p)基组,对甲酸与质子性溶剂分子形成的HCOOH-S_1-S_2(S_1和S_2分别为H_2O和NHF2)复合物在气相时发生的基态三质子转移反应过程进行了理论研究.4个甲酸复合物HCOOH-H_2O-H_2O,HCOOH-NHF2-NHF2,HCOOH-H_2O-NHF2及HCOOH-NHF2-H_2O中发生的三质子转移反应都是以异步协同质子迁移方式进行的.甲酸复合物中的氢键链组成和连接方式对基态三质子转移反应能垒有显著影响.HCOOH-S_1-S_2复合物中氢键链的质子接受能力可以表示为a×β1+b×β2(a+b=1).当a=0.45,b=0.55时,HCOOH-S_1-S_2中氢键链的质子接受能力和HCOOH-S_1-S_2复合物中的质子转移反应能垒成线性关系.氢键链的质子接收能力越强,反应能垒越低.     

氢键诱导侧链液晶高分子的分子理论

将自组装概念引入Flory-Huggins格子理论,导出定向混合的氢键诱导侧链液晶高分子体系在各向同性相的混合自由能和各组分的化学势;由Maier-Saupe平均场理论给出在向列相的混合自由能和各组分的化学势,建立了氢键诱导侧链液晶高分子的分子理论模型.计算结果表明,由于氢键的方向性和饱和性决定自组装体中主客体的容纳能力,在相图上出现一个峰值;提高氢键相互作用参数和增加羧基含量,不仅自组装体的热稳定性增加,而且峰值向小分子含量低的方向移动;聚合物分子量对自组装体的热稳定性影响存在一个临界值,超过临界值后,热稳定性与分子量无关.     

DFT和热力学研究氢键协同效应及对关联1H NMR的影响

用DFT方法在B3LYP／6—311 G(d,p)水平下研究了甲醇线性和环状分子簇．对于不同大小的分子簇之间定义了协同因子,计算得到的协同因子可以验证氢键的强协同效应,环状分子簇之间的协同效应远远大于线性分子簇,做为理论验证和比较,热力学模型分别采用含氢键缔合的格子流体状态方程(LFHB),以及含氢键协同效应的LFHB,关联醇一惰性体系的^1H核磁共振化学位移．考虑协同效应的关联结果优于原始的LFHB,比较量子化学计算的和热力学模型中采用的协同因子,认为甲醇和乙醇在溶液中更可能大部分以线性缔合形式存在。     

肾上腺素与二甲亚砜氢键作用的理论研究

The hydrogen bond is one of the most important intermolecular interactions playing an important role in intermolecular recognition processes essential to most biological systems. Adrenaline is an important catecholamine neurotransmitter in the mammalian central nervous system. Dimethyl sulphoxide can carry with it drugs across membranes. The geometries of adrenaline and six stable 1 : 1 complexes formed between adrenaline and dimethyl sulphoxide were optimized by Berny method at PM3 level and thus were optimized by density functional theory（B3LYP method）at the 6-31G,6-31G*,and 6-31+G* level respectively to obtain accurate structures. Single-point energies of all optimized molecular geometries were calculated to discuss the energies and structural parameters between reactants and products. All the binding energies have been corrected by the zero point vibrational energies（ZPVE）at varied basis set levels from 6-31G to 6-31 + G*. The results indicated that stronger hydrogen-bonded complexes were formed by molecular interaction between adrenaline and dimethyl sulphoxide. The calculation results can be better used to explain some experimental phenomena.     

铂配合物与DNA碱基对间相互作用的理论研究

用量子化学方法研究一系列Pt(II)配合物作用于嘌呤碱基N7位点后对Watson-Crick碱基对AT、GC的影响. 计算结果显示铂配体与碱基对AT、GC的作用以静电作用为主，同时极化作用也是影响GC碱基对的重要因素. 静电作用极大地增强了铂化嘌呤碱基与嘧啶碱基间的相互作用，而嘌呤碱基与嘧啶碱基间作用与未铂化碱基对作用相近. Pd(II) 和 Ni(II)的相关研究得到类似的结果. 碱基对间氢键作用“二阶微扰能”分析结果与氢键强弱变化一致.     

DFT study on the intermolecular interactions between Aun (n = 2–4) and thymine

Density functional B3LYP method with 6-31++G** basis set is applied to optimize the geometries of the luteolin, water and luteolin–(H₂O)_n complexes. The vibrational frequencies are also studied at the same level to analyze these complexes. We obtained four steady luteolin–H₂O, nine steady luteolin–(H₂O)₂ and ten steady luteolin–(H₂O)₃, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) are used to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are within −13.7 to −82.5 kJ/mol. The strong hydrogen bonding mainly contribute to the interaction energies, Natural bond orbital analysis is performed to reveal the origin of the interaction. All calculations also indicate that there are strong hydrogen bonding interactions in luteolin–(H₂O)_n complexes. The OH stretching modes of complexes are red-shifted relative to those of the monomer.     

HCN(HNC)与NH3, H2O和HF分子间相互作用的理论研究

在MP2/aug-cc-pVTZ水平上, 对HCN(HNC)与NH3, H2O和HF分子间可能存在的氢键型复合物进行了全自由度能量梯度优化, 通过在相同水平上的频率验证分析发现了稳定的分子间相互作用形式是HCN(HNC)作为质子供体或作为质子受体形成的复合物. 基组重叠误差对总相互作用能的影响均小于3.34 kJ/mol. 通过自然键轨道(NBO)分析, 研究了单体和复合物中的原子电荷和电荷转移对分子间相互作用的影响. 对称性匹配微扰理论(SAPT, Symmetry Adapted Perturbation Theory)能量分解结果表明, 在分子间相互作用中, 静电作用与诱导作用占主导地位, 而诱导作用与复合物的电荷转移之间具有良好的正相关性.     

1,2,3-三氮杂苯-水复合物氢键相互作用

Density functional theory B3LYP method with 6-31++G** basis was used to optimize the geometries of the ground states for 1,2,3-triazine-(H2O)n (n=1,2,3) complexes. All calculations indicate that the 1,2,3-triazine-water complexes in the ground states have strong hydrogen-bonding interaction, and the complex having a N…H-O hydrogen bond and a chain of water molecules which is terminated by a O…H-C hydrogen bond is the most stable. The H-O stretching modes of complexes are red-shifted relative to that of the monomer. In addition, the Natural bond orbit (NBO) analysis indicates that the intermolecular charge transfer between 1,2,3-triazine and water is 0.0222e, 0.0261e and 0.0273e for the most stable 1:1, 1:2 and 1:3 complexes, respectively. The first singlet (n, π*) vertical excitation energy of the monomer 1,2,3-triazine and the hydrogen-bonding complexes of 1,2,3-triazine-(H2O)n were investigated by time-dependent density functional theory.     

Hydrogen bonds: a comparison of semiempirical and ab initio treatments

H-bonding interactions calculated using the AM1, PM3 and SAM1 semiempirical molecular orbital methods are compared with the best available ab initio calculations for several intermolecular interactions of interest: acetic acid dimers, water/ acetylene, water/HCN, formaldehyde/acetylene, formaldehyde/HCN, ozone/acetylene, ozone/HCN, acetylacetone, melamine/ cyanuric acid, and nitromethane/ammonia. Experimental values are also presented where available. The energetic comparisons are based upon enthalpies of interaction from the ab initio calculations after counterpoise and vibrational corrections have been applied. Overall, AM1 seems to do best, except for O---H…O interactions, where none of the three methods excel.     

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.     

Counterpoise corrections to the interaction energy components in bimolecular complexes

A new definition of counterpoise corrections (CP) to the components of E evaluated with the Kitaura and Morokuma method is presented and tested on the (H₂O)₂ and (NH₃·HF) molecular systems with two different basis sets. The CP corrections are further decomposed into subsystems contributions, facilitating their interpretation and the elaboration of computationally simplified procedures.     

烟酸二聚体的结构与性质

用密度泛函理论B3LYP方法选取6-311+G(d,p)基组对烟酸-烟酸复合物进行了量子化学计算研究, 通过在相同水平下的频率振动分析发现了势能面上存在7个极小值点, 其最稳定构型1对应一N…H—O型强氢键, 其结合能在消除基组重叠误差后为-48.3 kJ·mol-1. 通过自然键轨道(NBO)分析, 研究了电荷转移及轨道相互作用. 通过自洽反应场(SCRF)理论中的极化连续模型(PCM)在介电常数分别为1.0(真空)、2.247(苯)、10.36(二氯乙烷)、20.7(丙酮)、32.63(甲醇)、78.39(水)的不同溶剂环境下重新优化烟酸复合物势能面上最稳定构型1, 研究了溶剂对烟酸复合物几何构型及结合能的影响. 发现溶剂化作用增大了烟酸复合物分子间的结合能, 导致N…H距离减小. 当溶液介电常数在1.0-32.63范围时, 溶剂效应十分显著, 当介电常数大于32.63后, 溶剂化作用趋于稳定.     

On the non-additivity of the basis set superposition error and how to prevent its appearance

An analytical consideration is made for the simplest possible model in which the BSSE problem may appear. The results demonstrate that BSSE cannot be corrected in any consistent manner by readjusting the monomer energies to the enlarged basis, because the energy effects caused by BSSE and by the true interactions are not additive. The way out is to correct BSSE, or prevent its appearance by an appropriate analysis and special treatment at the supermolecule level, permitting to keep the supermolecule problem consistent with the monomer calculations, as provided by the chemical Hamiltonian approach recently introduced.