HArF和HNO二聚体相互作用氢键的理论研究

用二阶微扰理论结合6-311+G**、6-311++G**和6-311++G(2d,2p)基组对氢键相互作用二聚体HNO···HArF进行研究．在MP2/6-311+G**、MP2/6-311++G**和MP2/6-311++G(2d,2p)水平上，利用标准方法和均衡校正方法对二聚体进行了几何优化、振动频率和相互作用能的计算．对于相互作用能采用G2MP2方法计算．计算结果表明存在两种稳定的二聚体HNO···HArF结构，在这两种结构中，Dimer I(H···F)比Dimer II(H···O)更加稳定．通过振动频率的计算表明，在Dimer I(H···F)中存在N-H···F蓝移氢键，在DimerII(H···O)中存在Ar-H···O红移氢键，并对蓝移氢键加以确认．利用电子密度拓扑学分析和自然键轨道分析对于氢键红移和蓝移进行了合理解释．     

C6H5COOH⋯X分子间氢键的理论研究

在B3LYP/6-311++G(3df,2p)理论水平,计算研究C6H5COOH...X分子间氢键的理论研究(X=H2O, HCOH, CH3COCH3, NH3, CH2NH和HCN)氢键体系。获得氢键复合物稳定结构、氢键相互作用能、振动频率、热力学性质等。计算结果表明,C6H5COO—H...X体系存在较强的O—H...O与O—H...N红移氢键。C6H5COO—H...X氢键复合物气态分子的自发形成过程温度不同,C6H5COOH...NH3和C6H5COOH...CH2NH 体系在室温下能自发进行,其余二聚体要在低温下才能自发进行。     

C6H5COOH⋯X分子间氢键的理论研究

在B3LYP/6-311++G(3df,2p)理论水平,计算研究C6H5COOH...X分子间氢键的理论研究(X=H2O, HCOH, CH3COCH3, NH3, CH2NH和HCN)氢键体系。获得氢键复合物稳定结构、氢键相互作用能、振动频率、热力学性质等。计算结果表明,C6H5COO—H...X体系存在较强的O—H...O与O—H...N红移氢键。C6H5COO—H...X氢键复合物气态分子的自发形成过程温度不同,C6H5COOH...NH3和C6H5COOH...CH2NH 体系在室温下能自发进行,其余二聚体要在低温下才能自发进行。     

1,1,3,3-四甲基脲—溶剂氢键复合物的理论研究

采用密度泛函理论在B3LYP/6-311++G(d,p)水平上对水、苯胺、氯仿与1,1,3,3-四甲基脲分子形成的1:1气相氢键复合物进行计算研究.结果表明,三种物质与1,1,3,3-四甲基脲形成的复合物存在氢键,表现为羰基氧原子的孤对电子与H—X(X=O,N,C)反键轨道的相互作用.氢键的形成使C=O和H—X的伸缩振动频率红移.在标准压力和298.15 K下,氢键复合物的形成是一个放热的非自发过程.     

气相中HOCl和O3分子间氯键和氢键的结构和性质

在DFT-B3LYP/6-311 G**水平上分别求得O3…ClOH氯键复合物和O3…HOCl氢键复合物势能面上的稳定构型.频率分析表明,与单体HOCl相比,分别在两种复合物中,Cl4-O5和H6-O5键伸缩振动频率发生红移,红移值分别为5.70和76.44cm-1.经MP2/6-311 G**水平计算的含BSSE和零点振动能校正的气相中相互作用能分别为-2.102和-4.920 kJ·mol-1.NBO分析表明,在O3…ClOH氯键复合物中,引起Cl4-05键变长的因素包括2种电荷转移:(1)LP(O1)1→σ*(C14-05);(2)LP(O1)2→σ*(Cl4-O5),其中LP(O1)2→σ*((Cl4-O5)转移占主要作用,总的结果是使σ*(Cl10-O11)的自然布居数增加了14.44 me;在O3…HOCl氢键复合物中也存在类似的电荷转移,结果使σ*(H6-O5)的自然布居数增加了18.09 me.NRT理论进行键序分析表明,在氯键复合物和氢键复合物中,Cl4-O5和H6-O5键的键序都减小,与红外光谱频率计算分析和NBO分析的结论一致.AIM理论分析表明,分别在两种复合物中,O1…Cl4间和O1…H6间都存在键鞍点,而且O1…Cl4和O1…H6的P(r)都较小,分别为0.0111和0.0152 a.u.,说明复合物中的氯键和氢键相互作用较弱.另外,O1…Cl4氯键和O1…H6氢键的Laplacian量(△)ρP(r)分别为0.0479和0.0641 a.u.,都是较小的正值,说明这两种相互作用都以静电作用为主.     

硝酸羟胺-(H_2O)_n复合物氢键相互作用的密度泛函研究

为研究硝酸羟胺-(H_2O)_n复合物的氢键作用,采用密度泛函B3LYP方法在6-311++G(d, p)基组水平上对硝酸羟胺-(H_2O)_n复合物的结构进行优化,采用MP2/6-311++G(d, p)方法,经基组叠加误差和零点能校正计算得到复合物的相互作用能.利用自然键轨道分析方法研究复合物氢键作用的本质,并对复合物中水分子的振动光谱进行分析.计算结果表明,硝酸羟胺-(H_2O)_n复合物存在着6个硝酸羟胺-H_2O稳定构型和8个硝酸羟胺-(H_2O)_2稳定构型,且最稳定构型的相互作用能分别为52.821 kJ·mol~(-1)和73.349 kJ·mol~(-1).在硝酸羟胺-(H_2O)_n复合物中,水中H-O伸缩振动频率明显红移,且红移增大的程度与复合物稳定化能的变化趋势基本一致.     

腺嘌呤-水分子团簇的理论研究

利用密度泛函理论在B3LYP/6-311++G(d , p)基组水平上对C5H5N5·(H2O)m (m=1~3)进行了优化与振动频率计算,得到了团簇的六种稳定结构. 应用AIM程序计算了三种最稳定结构的氢键临界点的拓扑参数,结果表明,O—H…N氢键的形成使得O—H之间电子密度减小,伸缩振动频率减小,产生了红移;N—H…O氢键的形成使得N—H之间的电子密度减小,键的强度变弱,伸缩振动频率变小,发生了红移. 利用veda4软件对团簇C5H5N5·(H2O)m (m=0~3)的红外光谱的振动频率进行模式指认,并对部分振动频率进行了比较.     

腺嘌呤-水分子团簇结构与振动频率的理论研究

利用密度泛函理论在B3LYP/6-311++G(d,p)基组水平上对C_5H_5N_5·(H_2O)m(m=1~3)进行了优化与振动频率计算,得到了团簇的六种稳定结构.应用AIM程序计算了三种最稳定结构的氢键临界点的拓扑参数,结果表明,O—H…N氢键的形成使得O—H之间电子密度减小,伸缩振动频率减小,产生了红移;N—H…O氢键的形成使得N—H之间的电子密度减小,键的强度变弱,伸缩振动频率变小,发生了红移.利用veda4软件对团簇C_5H_5N_5·(H_2O)m(m=0~3)的红外光谱的振动频率进行模式指认,并对部分振动频率进行了比较.     

CH3⊕ … Br-Y(Y=H, CCH, CN, NC)缺电子体系中Br原子参与的反向卤键相互作用

采用B3LYP/6-311++G(d,p)和MP2/6-311++G(d,p)理论方法研究了CH₃^⊕…Br-Y(Y=H, CCH, CN, NC) 缺电子体系中Br参与的反向卤键(IXB)结构. 四个IXB复合物中,MP2/6-311++G(d,p)水平上考虑了基组叠加误差的分子间相互作用能分别为218.87, 219.48, 159.18和143.05 kJ/mol,相对稳定性的递增顺序CH₃^⊕…BrCN相似文献   

甘氨酸与水分子间相互作用的理论研究

在密度泛函(DFT)B3LYP/6_311++G(3d,3p)水平,对中性甘氨酸的最小点结构Ip和H2O分子间可能存在的氢键复合物进行全自由度能量梯度优化,发现了三个氢键极小结构A、C和E,其中结构A为最稳定结构,它是H2O与甘氨酸的羧基(-COOH)形成两个氢键的结构,具有C1对称性.分别采用密度泛函理论(DFT)和MP2方法,在6-311++G(3d,3p)水平,对结构A的结构和结合能进行了比较计算,得到结合能ΔEDFT为-41.88 kJ/mol,ΔEMP2为-40.34 kJ/mol.     

HNO二聚体蓝移氢键的理论研究

利用分子轨道从头算理论和密度泛函理论结合不同理论基组对于N-H…O蓝移氢键进行了详细的研究.利用标准方法和均衡校正方法对二聚体进行了几何优化,振动频率和相互作用能的计算.拓扑学和自然键轨道理论对于蓝移氢键的本质进行分析.自然键轨道(NBO)分析表明,σ*(N-H)轨道上电子密度降低是电子密度重排效应的结果.分子内电子重排、轨道再杂化和电子受体内部结构重组共同作用结果导致了N-H的振动频率大幅蓝移现象的出现.     

Odd-even effect of the number of free valence electrons on the electronic structure properties of gold-thiolate clusters

ABSTRACT

It is essential to understand the intrinsic stability of the gold-thiolate clusters, which present extensive potential applications in many fields such as the catalysis, biomedicines and molecular machines. The electronic structures and aromaticity indexes of a series of Au_m(SH)_n (m, n?=?5–12) were comprehensively investigated through energetic, vibrational, magnetic, and electronic density properties, which are highly sensitive to the size and topological structure of the cluster. Generally, computational results of energy gap between the frontier molecular orbitals, normalized atomization energy (NAE), and electron localization function (ELF)-σ values exhibit the odd-even effect, in which clusters with the even number of free valence electrons, being reflected by the value of (m–n), possess relatively higher stability than the odd one. However, it is difficult to describe the stability of cluster with the sophisticated three-dimensional structure through one single aromaticity index such as the nucleus-independent chemical shift (NICS) value. Principal component analysis and clustering analysis of the calculation results of Au_m(SR)_n clusters suggest that the value of (m–n) and the Au₄ unit are important for predicting the stability of the Au clusters.     

Cooperative effects between tetrel bond and other σ–hole bond interactions: a comparative investigation

Covalently bonded atoms of Groups IV–VII tend to have anisotropic charge distributions, the electronic densities being less on the extensions of the bonds (σ–holes) than in the intervening regions. These σ–holes often give rise to positive electrostatic potentials through which the atom can interact attractively and highly directionally with negative sites. In this work, cooperative effects between tetrel bond and halogen/chalcogen/pnicogen bond interactions are studied in multi-component YH₃M···NCX···NH₃ complexes, where Y = F, CN; M = C, Si and X = Cl, SH and PH₂. These effects are analysed in detail in terms of the structural, energetic, charge-transfer and electron density properties of the complexes. The nature of the σ–hole bonds is unveiled by quantum theory of atoms in molecules and natural bond orbital theory. A favourable cooperativity is found with values that range between ?0.34 and ?1.15 kcal/mol. Many-body decomposition of interaction energies indicate that two-body energy term is the most important source of the attraction, which its contribution accounts for 87%–96% of the total interaction energy.     

Analysis of surface and bulk polymerization of a thin film using a chemical derivatization technique and TOF-SIMS

A chemical derivatization technique in TOF-SIMS along with ultra-low angle sample cutting technique were used to perform a quantitative study of the surface and in-depth double bond profile of the photo-initiated polymerized thin film. We found out that the characteristic peaks at m/z 185 and 199 were obtained from the thin film composed of acrylate monomer and methacrylate monomer, respectively, after reaction with bromine gas. The detection sensitivity of certain chemical indicators is affected by changing the primary ion species. The Bi₃⁺ primary ion results in the best chemical sensitivity. The surface double-bond density obtained by TOF-SIMS and the Br 3d signal intensity of XPS showed a good linear relationship in the limited region due to the effect of matrix hardness.The thin film was cut with microtome about 1° angle and was left to react with bromine and was measured using TOF-SIMS. It was clearly observed from this technique that double bond of acrylate and methacrylate monomer remained much more at the surface of the photo-initiated polymerized thin film, due to the inhibition of polymerization by oxygen. From the surface to 1 μm depth, both monomers show the same behavior, but the rate of polymerization of methacrylate monomer was lower than that of acrylate in deeper layers.     

金属Ni纳米线凝固行为的分子动力学模拟

采用EAM镶嵌原子作用势，通过经典的分子动力学模拟方法研究了不同冷却速度下的金属Ni纳米线的凝固行为，并给出了纳米线在凝固区域的结构演变过程.利用键对分析技术研究了在不同冷却速度下体系中的原子团簇在降温过程中的变化情况.研究表明，纳米线的凝固起始于表面原子，并且随着冷却速度的降低，Ni纳米线的微观结构从非晶态过渡到多壳螺旋结构，最终达到稳定的面心立方结构.多壳螺旋结构同时具有确定的结晶温度和长程无序、短程有序的非晶结构的特征. 关键词： 纳米线 凝固行为 分子动力学 键对分析     

Cooperative effects of hydrogen,halogen and beryllium bonds on model halogen-bonded FCl … YZ (YZ = BF,CO, N2) complexes in FX′ … FCl … YZ trimers (FX′ = FH,FCl, F2Be)

A computational study of model halogen-bonded FCl?…?YZ dimers and FX′?…?FCl?…?YZ (FX′ = FH, FCl, F₂Be; YZ = BF, CO, N₂) trimers was undertaken at the MP2/6-311++G (2d, 2p) level of theory. Three different trimer arrangements are possible and the cooperative effect of hydrogen-, halogen- and beryllium-bonding in each of these trimers was assessed relative to the FCl?…?YZ dimer. It was found that the beryllium bond has the largest cooperative effect, while the halogen bond has the smallest, with the hydrogen bond being intermediate between the other two interactions. Interesting trends in selected properties were identified and discussed.     

Tin(n=2~7)团簇结构, 稳定性和电荷分布关系的密度泛函研究

利用密度泛函理论中的B3LYP方法, 选择LANL2DZ基组优化Tin(2~7)团簇得到各团簇的稳定结构,然后对稳定结构的束缚能及自然轨道进行分析. 研究结果表明: Tin(n=2~7)团簇都依带帽的形式在前一个团簇的结构基础上加一个原子变化而来; 通过自然轨道分析发现, 团簇原子的轨道存在sp-d杂化, 有大约一个电子从4s转移到了3d, 原子之间亦存在电子转移, 而且除Ti7外, 团簇键长由最外层4d轨道电子和3d轨道共同决定, 在Ti7中, 团簇键长由3d轨道决定.     

取代基对N-H•••O=C氢键二聚体中氢键强度的影响

使用MP2方法研究了N-H•••O=C氢键二聚体的氢键强度,探讨了不同取代基对N-H•••O=C氢键强度的影响.研究发现,可以通过改变质子供体或受体分子上取代基的供电性或吸电性来调控氢键强度:乙基等供电子基团对N-H•••O=C氢键强度的调节作用不大;NO2和CN等强吸电子基团可极大地改变N-H•••O=C氢键强度;质子供体分子中的强吸电子基团如CN可使N-H•••O=C氢键强度增强多达4.6kcal/mol,质子受体分子中的强吸电子基团如NO2可使N-H•••O=C氢键强度减弱多达2.6kcal/mol.自然键轨道(NBO)分析表明,N-H•••O=C氢键强度越强,参与形成氢键的氢原子电荷越正,氧原子电荷越负,单体分子间电荷转移越多,N-H•••O=C氢键中氧原子孤对电子n(O)对N-H反键轨道σ*(N-H)的二阶稳定化能越大.     

取代基对N-H…O=C氢键二聚体中氢键强度的影响

使用MP2方法研究了N-H…O=C氢键二聚体的氢键强度,探讨了不同取代基对N-H…O=C氢键强度的影响.研究发现,可以通过改变取代基的供电性或吸电性来调控氢键强度:乙基等供电子基团对N-H…=C氢键强度的调节作用不大;-NO_2等强吸电子基团可极大地改变N-H…=C氢键强度;质子受体分子中的强吸电子基团如-NO_2可使N-H…O=C氢键强度减弱多达2.6 kcal/mol.自然键轨道(NBO)分析表明,N-H…O=C氢键强度越强,参与形成氢键的氢原子电荷越正,氧原子电荷越负,单体分子间电荷转移越多,N-H…O=C氢键中氧原子孤对电子n(O)对N-H反键轨道σ*(N-H)的二阶稳定化能越大.