应用ABEEM/MM模型研究水分子团簇(H2O)n(n=7~10)的性质

应用ABEEM/MM模型计算了中等大小水分子团簇(H₂O)_n(n=7~10)的各种性质, 如: 优化的几何构型、氢键个数、结合能、稳定性、ABEEM电荷分布、偶极矩、结构参数的描述等, 并描述了六聚水区域中所反映的从二维结构(从二聚水到五聚水)到三维结构(n>6的水分子团簇)的过渡.     

CnBδ(δ=0, ±1; n =1～6)团簇的结构、稳定性和光谱

采用密度泛函理论(DFT)的B3LYP方法,在6-31G*和6-311＋G(3df)水平上对C_nB(n=1～6)团簇及其阴离子和阳离子的几何构型和电子结构进行了优化和振动频率计算.得到了C_nB(n=1～6)团簇的电离能,绝热电子亲合势以及C_nB^δ(δ=0,±1)团簇的能隙.结果表明C_nB^－(n=1～6)团簇的基态构型均为线形,这与等电子的C_n簇合物的结构是一致的; C_nB(n=1～6)团簇的基态构型中,除C₂B为不对称的三角形,C₆B为具有C_2v对称性的环状结构外,其余均为线形结构.阳离子团簇中n=2、3、6的基态结构具有C_2v对称性外,其它几个均为线形结构.从几何参数和振动频率上发现,采用密度泛函B3LYP方法在6-311＋G(3df)和6-31G*两种基组上计算得到的键长参数和振动频率非常接近,说明B3LYP方法在计算C_nB簇合物结构参数上对于基组的选择是不太敏感的.通过对C_nB(n=1～6)的光电子能谱性质的研究发现,C₄B容易获得一个电子形成阴离子团簇,但失去一个电子是很困难的,这与实验上观测到的结果非常吻合.     

二聚体C2H4-nFn···LiH (n=0, 1, 2)中π锂键的性质和弱方向性

采用二级微扰理论(MP2)量子化学研究方法, 对C₂H_4-nF_n···LiH (n=0, 1, 2)二聚体的结构和π锂键性质进行了分析. 结果表明氟原子的取代改变了乙烯分子的π电子云形状, 从而使二聚体体系中的π锂键发生偏移、伸长和弯曲. 通过与类似的π氢键体系C₂H_4-nF_n···HF (n=0, 1, 2)比较, 发现π锂键在二级弱相互作用的影响下, 发生了明显的弯曲, 表现出弱的方向性. 在CCSD(T)/6-311++G(3df, 3pd)理论水平下, 二聚体的相互作用能强弱顺序为: 33.85 kJ·mol^-1 (C₂H₄-LiH)>27.32 kJ·mol^-1 (C₂H₃F-LiH)>21.34 kJ·mol^-1 (cis-C₂H₂F₂-LiH)>20.25 kJ·mol^-1 (g-C₂H₂F₂-LiH), 说明氟取代削减了乙烯分子与LiH之间的相互作用.     

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.     

包含两个平面五配位碳原子C2＋nB10－n (n＝0～10)团簇的结构的理论研究

采用B3LYP/6-311＋G**方法, 我们优化了初始构型中包含两个平面五配位碳原子(ppCs)的C_{2＋nB10－n (n＝0～10)团簇的结构并计算了它们的振动频率. 计算结果表明, C2＋nB10－n (n＝0～2)团簇是稳定的, 而且这三个结构中ppC—B键的Wiberg键级介于0.511～0.909之间, ppC—C键的Wiberg键级为0.2254 (n＝1)和0.8586 (n＝2), ppC的键级介于3.778到3.879之间, 即这三个结构中存在两个ppCs, 而且ppC遵循八隅规则; C2＋nB10－n (n＝3～6)团簇的最稳定结构包含一个ppC; C2＋nB10－n (n＞6)团簇能量最低结构中不存在ppC. 而且只有团簇C2＋nB10－n (n＝0～2)中没有悬键, 它们的(电子数分别为: 6, 7和8, 计算它们的NICS(0)值表明强芳香性一般位于局部的三元环中心, 表明局部离域有利于平面结构的形成. C2＋nB10－n (n＝0～2)团簇的第一垂直激发能分别为: 1.91, 0.56和3.12 eV.}     

TinO2和TinO2-(n=1-10)团簇的几何结构、电子和磁性质

基于密度泛函理论(DFT)的B3LYP方法, 研究了Ti_nO₂和Ti_nO₂^- (n=1-10)团簇的几何结构、电子结构以及磁性. 结果表明, 两个氧以分离的原子状态吸附在金属团簇的表面, 呈现出以一个钛原子为中心的O-Ti-O 的相邻吸附形式. 中性团簇和阴离子团簇的能量最低结构相似. 稳定性分析表明Ti_nO₂具有很高的稳定性, 特别是TiO₂和Ti₇O₂. 此外, 详细讨论了团簇的电离势、电子亲和能、电子解离能和能隙. 基于最低能量结构, 讨论了团簇的磁性, 发现电荷从Ti 原子向O原子转移, 并且电荷转移主要发生在Ti_nO₂的Ti-3d、Ti-4s和O-2p轨道. 磁性团簇中反铁磁序占据主导, 磁矩主要来源Ti-3d电子的贡献, 而两个氧原子的贡献非常小.     

应用ABEEM/MM模型研究水分子团簇(H2O)n (n=11～16)的性质

应用ABEEM/MM 模型计算了较大的水分子团簇(H2O)n (n=11~16)的各种性质,如：优化的几何构型, 氢键个数, 结合能, 稳定性, ABEEM 电荷分布, 偶极矩, 以及结构参数、平均氢键个数和强度, 增加的团簇结合能等.结果表明,从立方体结构到笼状结构的过渡出现在n=12的水分子团簇中,随着类似于笼状结构特点的不断增强,五元环的富集程度有所增加.     

Aun(n=2-9)团簇与乙醇分子相互作用的第一性原理研究

利用密度泛函理论研究了Au_n(n=2-9)团簇吸附一个乙醇分子的结构和电子性质. 研究结果表明: Au_n(n=2-9)团簇的最稳定构型为二维平面结构, Au6团簇最稳定; 吸附过程是通过金团簇上一个特定的金原子与乙醇分子中氧原子相互作用完成, 形成了20种稳定构型; 金原子的配位数对吸附作用影响明显; 作为吸附主体的金团簇和被吸附的乙醇分子在吸附前后构型无明显变化, 它们之间为弱相互作用.     

1,3-二(4-吡啶基)丙烷Cd(Ⅱ)配合物的合成、晶体结构及发光性质研究

以1, 3-二(4-吡啶基)丙烷(L)为配体,合成了一种新的Cd(Ⅱ)配合物{[CdL₂(H₂O)₂]·2(C₇H₆N₅)}_n(C₇H₆N₅=5-(3-氨基苯基)四唑离子)。X射线单晶衍射结构分析表明该配合物为一维链状结构,Cd(Ⅱ)分别与4个1, 3-二(4-吡啶基)丙烷配体的4个氮原子,2个配位水分子的氧原子形成了六配位的扭曲八面体几何构型,1, 3-二(4-吡啶基)丙烷配体桥梁相邻的Cd(Ⅱ)离子形成了一维的无限延伸的链状结构,分子间通过O-H…N、N-H…N氢键作用构筑成三维超分子网络结构。     

硼碳团簇BnC2 (n＝1～6)的理论研究

应用密度泛函理论在B3LYP/6-311＋G(d)水平上研究了硼碳团簇B_nC₂ (n＝1～6)的几何结构、生长机制和相对稳定性. 计算结果表明, 对于n＝2～6的簇, 平面多环状构型为最稳定的结构, 其中C原子分布于环的顶点、有尽可能多的三配位硼原子和尽可能多的B—C键. 碳原子作为杂原子倾向掺杂于团簇的顶点位置, 它的掺杂不改变硼团簇的主体结构. 与平面多环状结构相比, 随着簇尺寸的增大, 三维结构和线性链结构更不稳定. 在低能线性结构中, C原子位于链两侧的第二个位置. 计算的碎片分裂能、递增键能以及HOMO-LUMO能隙表明, B₄C₂为幻数簇.     

类硅烯H2C＝SiLiBr与RH (R＝F, OH, NH2)的插入反应

采用DFT B3LYP和QCISD方法研究了类硅烯H2C＝SiLiBr与RH (R＝F, OH, NH2)的插入反应. 在B3LYP/6- 311＋G(d,p)水平上优化了反应势能面上的驻点构型. 结果表明, H2C＝SiLiBr与HF, H2O或NH3发生插入反应的机理相同. QCISD/6-311＋＋G(d,p)//B3LYP/6-311＋G(d,p)计算的三个反应的势垒分别为148.62, 164.42和165.07 kJ•mol－1, 反应热分别为－69.63, －43.02和－28.27 kJ•mol－1. 相同条件下发生插入反应时, 反应活性都是H—F＞H—OH＞H—NH2.     

类锗烯H2C=GeLiCl与RH(R=F,OH, NH2)的插入反应

采用DFT B3LYP和QCISD方法研究了不饱和类锗烯H2C=GeLiCl与RH(R=F, OH, NH2)的插入反应. 在B3LYP/6-311+G(d,p)水平上优化了反应势能面上的驻点构型. 结果表明, H2C=GeLiCl与HF、H2O 或NH3发生插入反应的机理相同. QCISD/6-311++G(d,p)//B3LYP/6-311+G(d,p)计算的三个反应的势垒分别为173.53、194.48和209.05 kJ·mol-1, 反应热分别为60.18、72.93和75.34 kJ·mol-1. 相同条件下发生插入反应时, 反应活性顺序都是H—F>H—OH>H—NH2.     

Theoretical Studies on the Stabilities and Hydrogen Bond Actions of （H2O）n Clusters

1 INTRODUCTION In the latest ten years, the structure and function of water clusters have captured the interest of chemists. One of the most important study objects in water cluster is to describe the behavior of water so- lution quantitatively at molecule level, which will pave the way for the solving of some environmental and other scientific problems, such as the formation of acid rain and nucleation mechanism of little water drop. Besides, weak interaction in water clusters could be al…     

Comparison of hydrated hydroperoxide anion (HOO-)(H2O)n clusters with alkaline hydrogen peroxide (HOOH)(OH-)(H2O)(n-1) clusters, n = 1-8, 20: an ab initio study

Hydroperoxide anion (HOO(-)), the conjugate base of hydrogen peroxide (HOOH), has been relatively little studied despite the importance of HOOH in commercial processes, atmospheric science, and biology. The anion has been shown to exist as a stable species in alkaline water. This project explored the structure of gas phase (HOO(-))(H(2)O)(n) clusters and identified the lowest energy configurations for n ≤ 8 at the B3LYP/6-311++G** level of theory and for n ≤ 6 at the MP2/aug-cc-pVTZ level of theory. As a start toward understanding equilibration between HOO(-) and HOOH in an alkaline environment, (HOOH)(OH(-))(H(2)O)(n-1) clusters were likewise examined, and the lowest energy configurations were determined for n ≤ 8 (B3LYP/6-311++G**) and n ≤ 6 (MP2/aug-cc-pVTZ). Some studies were also done for n = 20. The two species have very different solvation behaviors. In low energy (HOOH)(OH(-))(H(2)O)(n-1) clusters, HOOH sits on the surface of the cluster, is 4-coordinated (each O is donor once and acceptor once), and donates to the hydroxide ion. In contrast, in low energy (HOO(-))(H(2)O)(n) clusters, (HOO(-)) takes a position in the cluster center surrounded on all sides by water molecules, and its optimum coordination number appears to be 7 (one O is donor-acceptor-acceptor while the other is a 4-fold acceptor). For n ≤ 6 the lowest (HOOH)(OH(-))(H(2)O)(n-1) cluster lies 1.0-2.1 kcal/mol below the lowest (HOO(-))(H(2)O)(n) cluster, but the lowest clusters found for n = 20 favor (HOO(-))(H(2)O)(20). The results suggest that ambient water could act as a substantial kinetic brake that slows equilibration between (HOOH)(OH(-)) and (HOO(-))(H(2)O) because extensive rearrangement of solvation shells is necessary to restabilize either species after proton transfer.     

Theoretical Studies on the Intermonomer Interaction of F~-·(H_2O)_n (n = 1, 2)

1 INTRODUCTION Hydrogen bond plays an important role in the fields of physics, biology and chemistry. It has cap- tured the interest of chemists for a long time and reports about its theory and experiment have been well represented[1～6]. Concerning its theoretical inves- tigations, most of the emphases are placed on the weak interaction energy of intramolecular hydrogen bond. But studies on its spectrum behavior are rela- tively rare. These years spectrum behavior led by hydrogen bond h…     

IR spectroscopy of hydrogen-bonded 2-fluoropyridine-methanol clusters

The electronic and infrared spectra of 2-fluoropyridine-methanol clusters were observed in a supersonic free jet. The structure of hydrogen-bonded clusters of 2-fluoropyridine with methanol was studied on the basis of the molecular orbital calculations. The IR spectra of 2-fluoropyridine-(CH3OH)n(n = 1-3) clusters were observed with a fluorescence-detected infrared depletion (FDIR) technique in the OH and CH stretching vibrational regions. The structures of the clusters are similar to those observed for 2-fluoropyridine-(H2O)n (n = 1-3) clusters. The existence of weak hydrogen bond interaction through aromatic hydrogen was observed in the IR spectra. The theoretical calculation also supports the result. The vibrational frequencies of CH bonds in CH3 group are affected by hydrogen bond formation although these bonds do not directly relate to the hydrogen bond interaction. The B3LYP/6-311 ++G(d,p) calculations reproduce well the vibrational frequency of the hydrogen-bonded OH stretching vibrations. However, the calculated frequency of CH stretching vibration could not reproduce the IR spectra because of anharmonic interaction with closely lying overtone or combination bands for nu3 and nu9 vibrations. The vibrational shift of nu2 vibration is reproduced well with molecular orbital calculations. The calculation also shows that the frequency shift of nu2 vibration is closely related to the CH bond length at the trans position against the OH bond in hydrogen-bonded methanol.     

Energetics of the O-H bond and of intramolecular hydrogen bonding in HOC6H4C(O)Y (Y = H, CH3, CH2CH=CH2, C[triple bond]CH, CH2F, NH2, NHCH3, NO2, OH, OCH3, OCN, CN, F, Cl, SH, and SCH3) compounds

The energetics of the phenolic O-H bond in a series of 2- and 4-HOC 6H 4C(O)Y (Y = H, CH3, CH 2CH=CH2, C[triple bond]CH, CH2F, NH2, NHCH 3, NO2, OH, OCH3, OCN, CN, F, Cl, SH, and SCH3) compounds and of the intramolecular O...H hydrogen bond in 2-HOC 6H 4C(O)Y, was investigated by using a combination of experimental and theoretical methods. The standard molar enthalpies of formation of 2-hydroxybenzaldehyde (2HBA), 4-hydroxybenzaldehyde (4HBA), 2'-hydroxyacetophenone (2HAP), 2-hydroxybenzamide (2HBM), and 4-hydroxybenzamide (4HBM), at 298.15 K, were determined by micro- or macrocombustion calorimetry. The corresponding enthalpies of vaporization or sublimation were also measured by Calvet drop-calorimetry and Knudsen effusion measurements. The combination of the obtained experimental data led to Delta f H m (o)(2HBA, g) = -238.3 +/- 2.5 kJ.mol (-1), DeltafHm(o)(4HBA, g) = -220.3 +/- 2.0 kJ.mol(-1), Delta f H m (o)(2HAP, g) = -291.8 +/- 2.1 kJ.mol(-1), DeltafHm(o)(2HBM, g) = -304.8 +/- 1.5 kJ.mol (-1), and DeltafHm(o) (4HBM, g) = -278.4 +/- 2.4 kJ.mol (-1). These values, were used to assess the predictions of the B3LYP/6-31G(d,p), B3LYP/6-311+G(d,p), B3LYP/aug-cc-pVDZ, B3P86/6-31G(d,p), B3P86/6-311+G(d,p), B3P86/aug-cc-pVDZ, and CBS-QB3 methods, for the enthalpies of a series of isodesmic gas phase reactions. In general, the CBS-QB3 method was able to reproduce the experimental enthalpies of reaction within their uncertainties. The B3LYP/6-311+G(d,p) method, with a slightly poorer accuracy than the CBS-QB3 approach, achieved the best performance of the tested DFT models. It was further used to analyze the trends of the intramolecular O...H hydrogen bond in 2-HOC 6H 4C(O)Y evaluated by the ortho-para method and to compare the energetics of the phenolic O-H bond in 2- and 4-HOC 6H 4C(O)Y compounds. It was concluded that the O-H bond "strength" is systematically larger for 2-hydroxybenzoyl than for the corresponding 4-hydroxybenzoyl isomers mainly due to the presence of the intramolecular O...H hydrogen bond in the 2-isomers. The observed differences are, however, significantly dependent on the nature of the substituent Y, in particular, when an intramolecular H-bond can be present in the radical obtained upon cleavage of the O-H bond.     

Theoretical and kinetic study of the H + C2H5CN reaction

The reaction of H radical with C₂H₅CN has been studied using various quantum chemistry methods. The geometries were optimized at the B3LYP/6‐311+G(d,p) and B3LYP/6‐311++G(2d,2p) levels. The single‐point energies were calculated using G3 and BMC‐CCSD methods based on B3LYP/6‐311++G(2d,2p) geometries. Four mechanisms were investigated, namely, hydrogen abstraction, C‐addition/elimination, N‐addition/elimination and substitution. The kinetics of this reaction were studied using the transition state theory and multichannel Rice‐Ramsperger‐Kassel‐Marcus methodologies over a wide temperature range of 200–3000 K. The calculated results indicate that C‐addition/elimination channel is the most feasible over the whole temperature range. The deactivation of initial adduct C₂H₅CHN is dominant at lower temperature with bath gas H₂ of 760 Torr; whereas C₂H₅+HCN is the dominant product at higher temperature. Our calculated rate constants are in good agreement with the available experimental data. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

A combined spectroscopic and theoretical study of propofol[middle dot](H(2)O)(3)

Propofol (2,6-di-isopropylphenol) is probably the most widely used general anesthetic. Previous studies focused on its complexes containing 1 and 2 water molecules. In this work, propofol clusters containing three water molecules were formed using supersonic expansions and probed by means of a number of mass-resolved laser spectroscopic techniques. The 2-color REMPI spectrum of propofol[middle dot](H(2)O)(3) contains contributions from at least two conformational isomers, as demonstrated by UV/UV hole burning. Using the infrared IR/UV double resonance technique, the IR spectrum of each isomer was obtained both in ground and first excited electronic states and interpreted in the light of density functional theory (DFT) calculations at M06-2X/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The spectral analysis reveals that in both isomers the water molecules are forming cyclic hydrogen bond networks around propofol's OH moiety. Furthermore, some evidences point to the existence of isomerization processes, due to a complicated conformational landscape and the existence of multiple paths with low energy barriers connecting the different conformers. Such processes are discussed with the aid of DFT calculations.