氨及其氟取代物与氟化氢形成氢键络合物的系列理论研究

采用ａｂ ｉｎｉｔｉｏ方法，在６－３１Ｇ水平上，对ＮＨ３…ＮＦ、ＮＨ２Ｆ…ＨＦ、ＮＦ３…ＨＦ４种氢键络合物的５组构型进行了一系列能量梯度法的构型优化和能量计算，取得到关于这些分子络合物的结构特征，氢键键能与键级，单体电荷迁移量等信息，分析，比较得出了在每种构型下各体系的重要物理量随氟基数的递变规律，并探讨了氟基的诱导效应对上述体系氢键作用的影响。     

水分子体系中用解析函数拟合质子转移势能的理论研究

采用量子化学ab initio(4-31G基组)计算方法,求得水分子体系(H_2O…H~ …OH_2)在氢键取不同方向和长度情况下的质子转移势能,它们均具有双势阱特征.寻找合理的解析函数形式,拟合上述的ab initio计算结果,以扩大其适用性.拟合相关系数可达0.999.拟合参数受氢键取向影响不大,但对氢键长度变化较敏感.     

XH···HOCl···YH体系中氢键与卤键协同效应的理论研究

采用MP2方法在6-311++G(d,p)基组水平上对三分子体系XH…HOCl…YH(X=F,Cl,Br,OH;Y=F,Cl,Br,OH,NH2)中氢键和卤键之间的协同效应进行了研究。研究过程中计算了二体XH…HOCl中氢键,二体HOCl…YH中卤键和三体XH…HOCl…YH中氢键和卤键的键长、分子间的相互作用能以及它们的振动频率。发现和二体相比,三体中氢键和卤键的键长缩短,分子间的相互作用能增大,振动频率增大。再通过AIM分析,比较了二体、三体中氢键和卤键键鞍点处电子密度强弱的变化,结果电子密度在三体中明显增大,分析结果还显示氢键和卤键属于分子间弱相互作用的范畴,它们的静电作用和二体相比也有所增强。这些现象都表明三体中氢键和卤键之间存在正的协同效应。     

水溶液中氨基酸侧链对G∶C碱基对间氢键影响的理论研究

利用量子化学方法研究了气相和水溶液下,氨基酸侧链与鸟嘌呤和胞嘧啶间的氢键作用.应用B3LYP/6-31+G(d,p)方法优化复合物几何结构,使用MP2/aug-cc-p VDZ方法进行复合物能量、自然键轨道(NBO)电荷和二阶稳定化能的计算.结果表明,水溶液可使氨基酸侧链与碱基或碱基对之间氢键键能显著减小;带电复合物气相和水溶液氢键键能之差范围为50.63~146.48 k J/mol,中性为0.17~24.94 k J/mol;电荷的转移量与氢键键能成正比,电荷转移量越多,复合物越稳定;二阶稳定化能与氢键键长成反比,与电荷转移量成正比,且气相与水溶液氢键二阶稳定化能之比约为两相的电荷转移量之比.水溶液对该类体系中氢键作用具有明显影响.     

醇及脱氧核糖与水分子间三体作用强度的快速准确计算

快速准确预测醇及脱氧核糖分子与水形成的氢键复合物的三体作用强度, 对准确模拟水环境下蛋白质和DNA的结构和功能至关重要. 基于对多体极化作用的理解, 在可极化偶极-偶极作用模型(PBFF)基础上, 将体系中的极性化学键视为化学键偶极, 通过模拟键偶极的极化计算了醇及脱氧核糖与水分子形成的氢键复合物的三体作用能. 通过拟合甲醇与水氢键复合物的三体作用能随分子间距离变化的能量曲线确定了所需的参数. 将模型和所确定的参数应用于计算更多的甲醇、 乙醇及脱氧核糖与水氢键复合物的三体作用能, 检验了模型的准确性和参数的可转移性. 计算结果表明, 可极化偶极-偶极作用模型及所确定的参数能够较好地预测具有不同结构的氢键复合物的三体作用强度, 其精度可与MP2方法的计算精度相当.     

金属丝桃蒽酮结构变化的理论研究

用MMX和AM1方法对金属桃蒽酮(HYP)结构变化过程的生成热进行了计算.发现:1.HYP1,2位OH可越过20kJ/mol左右的势,绕C--O键旋转而形成分子内氢键,并估算出键能约为10kJ/mol;2.HYP其他四个OH也可进行类似的构象变化,势垒在26kJ/mol左右,相应分子内氢键键能约为20kJmol;3.HYP分子内氢传递产生的异构体在能量上不稳定,进而在基础上探讨了1,2位OH分子内氢键的形成对HYP光敏活性的影响。     

金属丝桃蒽酮结构变化的理论研究

用MMX和AM1方法对金属桃蒽酮(HYP)结构变化过程的生成热进行了计算.发现:1.HYP1,2位OH可越过20kJ/mol左右的势,绕C--O键旋转而形成分子内氢键,并估算出键能约为10kJ/mol;2.HYP其他四个OH也可进行类似的构象变化,势垒在26kJ/mol左右,相应分子内氢键键能约为20kJmol;3.HYP分子内氢传递产生的异构体在能量上不稳定,进而在基础上探讨了1,2位OH分子内氢键的形成对HYP光敏活性的影响。     

CaH_2…HY（Y=CH_3,C_2H_3,C_2H,CN,NC）体系双氢键性质的理论研究

在B3LYP/6-311＋＋G（3df,2p）及MP2/6-311＋＋G（3df,2p）水平上探讨了以CaH2为质子受体及多种常见质子供体构成的CaH2…HY（Y=CH3,C2H3,C2H,CN,NC）弱相互作用体系的几何结构以及所形成的双氢键的性质.MP2方法计算得到线型的CaH2分子结构,在B3LYP方法计算下优化得到的CaH2部分则是一个非常明显的弯曲结构.NBO分析计算表明,线型结构（MP2）中Ca原子杂化轨道主要源自于sp杂化而弯曲结构（B3LYP）则主要为sd杂化,这与之前报道的相关研究结论相一致.基于不同CaH2分子结构计算得到的CaH2…HY体系的H…H间距离、相互作用能以及电荷转移性质等非常接近.MP2和B3LYP方法计算得到的CaH2…HY体系H…H间距离均处于0.15～0.24nm,相互作用能处于1～44kJmol-1范围.CaH2…HY体系的相互作用能变化趋势为CaH2…CH4-CaH2…C2H4-CaH2…C2H2-CaH2…HCN-CaH2…HNC,H…H距离的变化规律与相互作用能变化趋势相反,即键能越大H…H距离越小.相较于HY单体,形成的CaH2…HY复合物体系的质子供体键H-Y的键长增大,质子供体的键长增加量△r（H-Y）与H…H间距离间有这样的关系：H…H间距离越小,△r（H-Y）越大.双氢键AIM拓扑数据表明形成CaH2…HY复合物后,Ca-H键临界点的电子密度（ρc）较单体时减小且与双氢键相互作用能成线性关系,即复合物中Ca-H键临界点的ρc数值越小同时双氢键键能越大.NPA结果表明,CaH2…HY体系中分子间的电荷转移总量随键能增大而增大.通过H…H间距离、相互作用能以及AIM分析,我们认为CaH2…CH4和CaH2…C2H4体系可划分为弱的范德华相互作用,而CaH2…C2H2,CaH2…HCN和CaH2…HNC体系形成的双氢键强度上相当于常规氢键,且最值得注意的是CaH2分子结构的差异性对CaH2…HY体系性质的影响微乎其微.     

C6H5—H…X分子间氢键的理论计算

利用密度泛函理论B3LYP方法, 在6-311+G(3df,2p)水平上对C6H5—H…X型分子间氢键进行了几何构型优化、氢键相互作用能、电子密度分布等计算. 其中C6H6为质子供体, HCOH、H2O、NH3、CH2NH和HCN为质子受体. 从电荷布居分析、自然键轨道等角度详细地讨论了C6H5—H…X 体系中, 共轭π键、O和N的不同键型结构对氢键形成的影响以及孤电子对与C—H 反键轨道之间的相互作用(n→σ*)等.     

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.     

A luminescent bis(pyridyl)‐substituted benzimidazole platinum(II) complex exhibiting an intermolecular anagostic interaction

The photophysical properties of transition metal complexes of the 5,6‐dimethyl‐2‐(pyridin‐2‐yl)‐1‐(pyridin‐2‐ylmethyl)‐1H‐benzimidazole ligand are of interest. Dichlorido[5,6‐dimethyl‐2‐(pyridin‐2‐yl)‐1‐(pyridin‐2‐ylmethyl)‐1H‐benzimidazole‐κ²N ²,N ³]platinum(II), [PtCl₂(C₂₀H₁₈N₄)], is luminescent in the solid state at room temperature. The compound displays a distorted square‐planar coordination geometry. The Pt—N(imidazole) bond length is shorter than the Pt—N(pyridine) bond length. The extended structure reveals that symmetry‐related molecules display weak C—H…N, C—H…Cl, and C—H…Pt hydrogen‐bonding interactions that are clearly discernable in the Hirshfeld surface and fingerprint plots. The intermolecular C—H…Pt and C—H…N interactions have been explored using density functional theory. The result of an analysis of the distance dependence of C—H…Pt yields a value consistent with that observed in the solid‐state structure. The energy of interaction for the C—H…Pt interaction is found to be about −11 kJ mol⁻¹.     

Syntheses and Crystal Structures of Some Aryloxy and Alkoxy Substituted Phthalonitriles

Phthalonitriles substituted with aryloxy and alkoxy groups have been synthesized and characterized by elemental analyses, IR, mass spectra and 1H NMR spectroscopy. And four of such crystal structures have also been determined. In the crystal structures, the major inter- molecular interactions between the neighboring molecules are the hydrogen bonds as C≡N···H and C-O···H that lead to similar networks in the crystal structures.     

磷炔R-C≡P(R=－BH2,－CH3,－NH2,－OH)及其异构体的稳定性

采用B3LYP和CCSD(T)方法对R－C≡P(R=－BH2, －CH3,－NH2, －OH)体系进行了理论研究.结果表明，含C≡P三键的异构体BH2－C≡P和CH3－C≡P在各自的体系中分别是热力学最稳定的结构.而在HO－C≡P和NH2－C≡P体系中，热力学最稳定的结构却是H－P=C=O和含C≡N三键的N≡C－PH2.动力学理论研究表明，没有相关实验研究的R－C≡P(R=－BH2, NH2)体系中共有5种异构体是动力学稳定的. 在HO－C≡P体系的2种动力学稳定的异构体中， H－P=C=O连接方式的异构体已被实验所证实，而另外一种HO－C≡P连接方式的异构体的动力学稳定性较高，实验中可以观察到.对于CH3C≡P体系，研究所预示的2种动力学稳定的异构体中CH3－C≡P已被实验证实，从理论上推测另一种动力学稳定性较高的异构体HC≡C－PH2在实验中也可以检测到.     

吡啶与HCl和CHCl3形成分子间红移氢键和蓝移氢键的理论研究

采用量子化学从头算的MP2方法, 分别在6-31G(d,p), 6-311+G(d,p)和AUG-cc-pVDZ基组下, 研究了复合物C5H5N…HCl(1), C5H5N…HCCl3(2)和C5H5N…HCCl3(3)的分子间氢键. 计算结果表明, 在复合物1中, HCl中Cl—H键伸长, 形成Cl—H…N红移氢键; 在复合物2中, HCCl3中C—H键伸长, 形成C—H…N 红移氢键; 在复合物3中, HCCl3中C—H键收缩, 形成C—H…π蓝移氢键. 自然键轨道(NBO)分析表明, 影响氢键红移和氢键蓝移主要有3个因素: n(Y)→σ*(X—H)超共轭作用、X—H键轨道再杂化和质子供体电子密度重排. 其中, 超共轭作用属于键伸长效应, 电子密度重排和轨道再杂化属于键收缩效应. 在复合物1和2中, 由于键伸长效应处于优势地位导致形成红移氢键; 在复合物3中, 由于键收缩效应处于优势地位导致形成蓝移氢键.     

Interplay of noncovalent interactions in antiseptic quaternary ammonium surfactant Miramistin

The molecular and crystal structure of the widely used antiseptic benzyldimethyl{3‐[(1‐oxotetradecyl)amino]propyl}ammonium chloride monohydrate (Miramistin, MR ), C₂₆H₄₇N₂O⁺·Cl^?·H₂O, was determined by a single‐crystal X‐ray diffraction study and analyzed in the framework of the QTAIM (quantum theory of atoms in molecules) approach using both periodic and molecular DFT (density functional theory) calculations. The various noncovalent intermolecular interactions of different strengths were found to be realized in the hydrophilic parts of the crystal packing (i.e. O—H…Cl, N—H…Cl, C—H…Cl, C—H…O and C—H…π). The hydrophobic parts are built up exclusively by van der Waals H…H contacts. Quantification of the interaction energies using calculated electron‐density distribution revealed that the total energy of the contacts within the hydrophilic and hydrophobic regions are comparable in value. The organic MR cation adopts the bent conformation with the head group tilted back to the long‐chain alkyl tail in both the crystalline and the isolated state due to stabilization of this geometry by several intramolecular C—H…π, C—H…N and H…H interactions. This conformation preference is hypothesized to play an important role in the interaction of MR with biomembranes.     

OCS,CO2,N2O与烯、炔烃之间π…π作用的电子密度拓扑研究

采用MP2/aug-cc-pVDZ方法对氧硫化碳(OCS)、二氧化碳(CO2)、一氧化二氮(N2O)与乙烯(C2H4)、乙炔(C2H2)、2-丁炔(C4H6)之间形成的平行构型复合物中的分子间相互作用进行了理论研究.复合物的相互作用能按照B…C2H4B…C2H2>B…C4H6(B=OCS,CO2,N2O)的顺序依次减小.采用电子密度拓扑分析理论方法,讨论了复合物中π…π作用的成键特性.电子密度拓扑分析表明复合物中形成了弱的分子间相互作用,且以静电作用为主;π电子密度分子图与全电子密度分子图中键径方向是一致的,说明π…π作用在本文所讨论的体系中起着很重要的作用.NBO分析表明净电荷迁移从电子给体C2H4,C2H2,C4H6到电子受体OCS,CO2,N2O,迁移数按照B…C2H4相似文献   

The synergistic co‐operation of N—H…O=P hydrogen bonds and C—H…OX weak intermolecular interactions (X is =P or —C) in the (CH3O)2P(O)(NH–NHC6F5) amidophosphoester: a combined X‐ray crystallographic and theoretical study

The asymmetric unit of O,O′‐dimethyl [(2,3,4,5,6‐pentafluorophenyl)hydrazinyl]phosphonate, C₈H₈F₅N₂O₃P, is composed of two symmetry‐independent molecules with significant differences in the orientations of the C₆F₅ and OMe groups. In the crystal structure, a one‐dimensional assembly is mediated from classical N—H…O hydrogen bonds, which includes R₂²(8), D(2) and some higher‐order graph‐set motifs. By also considering weak C—H…O=P and C—H…O—C intermolecular interactions, a two‐dimensional network extends along the ab plane. The strengths of the hydrogen bonds were evaluated using quantum chemical calculations with the GAUSSIAN09 software package at the B3LYP/6‐311G(d,p) level of theory. The LP(O) to σ*(NH) and σ*(CH) charge‐transfer interactions were examined according to second‐order perturbation theory in natural bond orbital (NBO) methodology. The hydrogen‐bonded clusters of molecules, including N—H…O and C—H…O interactions, were constructed as input files for the calculations and the strengths of the hydrogen bonds are as follows: N—H…O [R₂²(8)] > N—H…O [D(2)] > C—H…O. The decomposed fingerprint plots show that the contribution portions of the F…H/H…F contacts in both molecules are the largest.     

Supramolecular hydrogen‐bonding patterns in the organic–inorganic hybrid compound bis(4‐amino‐5‐chloro‐2,6‐dimethylpyrimidinium) tetrathiocyanatozinc(II)–4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine–water (1/2/2)

Zinc thiocyanate complexes have been found to be biologically active compounds. Zinc is also an essential element for the normal function of most organisms and is the main constituent in a number of metalloenzyme proteins. Pyrimidine and aminopyrimidine derivatives are biologically very important as they are components of nucleic acids. Thiocyanate ions can bridge metal ions by employing both their N and S atoms for coordination. They can play an important role in assembling different coordination structures and yield an interesting variety of one‐, two‐ and three‐dimensional polymeric metal–thiocyanate supramolecular frameworks. The structure of a new zinc thiocyanate–aminopyrimidine organic–inorganic compound, (C₆H₉ClN₃)₂[Zn(NCS)₄]·2C₆H₈ClN₃·2H₂O, is reported. The asymmetric unit consist of half a tetrathiocyanatozinc(II) dianion, an uncoordinated 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidinium cation, a 4‐amino‐5‐chloro‐2,6‐dimethylpyrimidine molecule and a water molecule. The Zn^II atom adopts a distorted tetrahedral coordination geometry and is coordinated by four N atoms from the thiocyanate anions. The Zn^II atom is located on a special position (twofold axis of symmetry). The pyrimidinium cation and the pyrimidine molecule are not coordinated to the Zn^II atom, but are hydrogen bonded to the uncoordinated water molecules and the metal‐coordinated thiocyanate ligands. The pyrimidine molecules and pyrimidinium cations also form base‐pair‐like structures with an R₂²(8) ring motif via N—H…N hydrogen bonds. The crystal structure is further stabilized by intermolecular N—H…O, O—H…S, N—H…S and O—H…N hydrogen bonds, by intramolecular N—H…Cl and C—H…Cl hydrogen bonds, and also by π–π stacking interactions.     

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.     

How short can the H...H intermolecular contact be? New findings that reveal the covalent nature of extremely strong interactions

Ab initio calculations at the MP2/6-311++G(d,p) and MP2/aug-cc-pVDZ//MP2/aug-cc-pVTZ levels have been performed for the following complexes: H2OH+...HBeH, H2OH+...HBeBeH, H2OH+...HBeF, HClOH+...HBeH, Cl2OH+...HBeH, and Cl2OH+...HBeF. For all dimers considered, extremely short H...H intermolecular contacts (1.0-1.3 A) were obtained. These are the shortest intermolecular distances which have ever been reported, with binding energies within the range of 13.7-24.3 kcal/mol (MP2/aug-cc-pVDZ//MP2/aug-cc-pVTZ level). The interaction energies of the complexes analyzed were also extrapolated to the complete basis set (CBS) limit. To explain the nature of such strong interactions, the Bader theory was applied, and the characteristics of the bond critical points (BCPs) were analyzed. It was pointed out that for the major part of the H...H contacts considered here the Laplacian of the electron density at H...H BCP is negative indicating the partly covalent nature of such a connection. The term "covalent character of the hydrogen bond" used sometimes in recent studies is discussed. An analysis of the interaction energy components for dihydrogen bonded systems considered indicates that in contrast to conventional hydrogen bonded systems the attractive electrostatic term is outweighed by the repulsive exchange energy term and that the higher order delocalization energy term is the most important attractive term.