乙腈、苯基氰在Cu(111)与Pd(100)表面上的吸附与反应

用高分辨电子能量损失谱(HREELS~*)对CH_3CN(乙腈)及C_6H_5CN(苯基氰)在清洁与氧覆盖的Cu(111)及Pd(100)表面上的吸附及其反应进行了研究。从198 K时CH_3CN吸附在Cu(111)及Pd(100)表面上的高分辨电子能量损失谱(HREELS)中观察到v(C≡N)几乎消失, 并在195 meV处出现一个较弱的v(C=N)谱带, 表明CH_3CN在吸附过程中C≡N再杂化为C=N,C,N原子分别与金属表面原子键合并C=N平行于表面。从198 K时C_6H_5CN在Pd(100)及Cu(111)上的HREELS表明C_6H_5CN的环平面与CN平行于金属表面。在185K时C_6H_5CN在氧覆盖的Pd(100)表面上的HREELS与其在清洁表面上的相似。并未观察到覆盖氧增强了C_6H_5CN在Pd(100)上的吸附及其它效应。C_6H_5CN吸附在氧覆盖的Cu(111)表面上产生了C_6H_5CNO的特征谱带。     

Enantiospecific desorption of chiral compounds from chiral Cu(643) and achiral Cu(111) surfaces

Temperature-programmed desorption (TPD) experiments have been conducted to investigate enantiospecific desorption from chiral single-crystal surfaces. The (643) and (six four three) planes of face-centered cubic metals such as Cu have kinked and stepped structures which are nonsuperimposable mirror images of one another and therefore are chiral. These chiral surfaces are denoted Cu(643)(R) and Cu(643)(S). We have observed that the desorption energies of (R)-3-methylcyclohexanone and (R)- and (S)-propylene oxides from the Cu(643)(R) and Cu(643)(S) surfaces depend on the relative handedness of the adsorbate/substrate combination. Since the (643) surface is comprised of terraces with local (111) orientation which are separated by kinked monatomic steps, it is instructive to perform TPD experiments with these chiral compounds on the achiral Cu(111) surface. These experiments have given some insight into the adsorption sites for the chiral molecules on the Cu(643) surfaces. There are several high-temperature features in the TPD spectra of the chiral compounds that only appear in the spectra from the (643) surfaces and thus are attributed to molecules adsorbed at or near the kinked steps. In addition there are lower temperature desorption features observed on the Cu(643) surfaces which occur in the same temperature range as desorption features observed on the Cu(111) surface. These features observed on the (643) surfaces are attributed to desorption from the flat (111) terraces.     

Scanning tunneling microscope imaging of (CH3S)2 on Cu(111)

Scanning tunneling microscope (STM) images of isolated molecules of dimethyl disulfide, (CH(3)S)(2), adsorbed on the Cu(111) surface were successfully obtained at a sample temperature of 4.7 K. A (CH(3)S)(2) molecule appears as an elliptic protrusion in the STM images. From density functional theory calculation, it was suggested that the bright part in the protrusion corresponds to the molecular orbital which is widely spread around H atoms in each CH(3) group in the (CH(3)S)(2) molecule. The STM images revealed that the molecules have a total of six equivalent adsorption orientations on Cu(111), which are given by the combination of three equivalent adsorption sites and two conformational isomers for each adsorption site.     

一氧化碳共吸附法确定叔丁胺分子在Cu(111)表面的吸附位

采用扫描隧道显微镜(STM)和密度泛函理论(DFT)研究了78 K时单个叔丁胺分子在Cu(111)表面的吸附位. 我们提出以共吸附的一氧化碳√3 ×√3 超结构为基底铜原子的标识方法, 确定了低覆盖度的叔丁胺分子在Cu(111)表面的吸附位为顶位. 而采用单个一氧化碳分子标识基底铜原子的位置, 同样得出了叔丁胺分子的吸附位为顶位. 此外, 还采用DFT计算叔丁胺分子在Cu(111)表面的优势吸附构型. 理论计算结果表明顶位吸附构型为能量最稳定的构型, 与实验结果相吻合.     

吸附氢气后的钯团簇在氧化亚铜表面上的稳定性研究

为了探究吸附H2后的Pdn团簇在Cu2O（111）完整表面和铜缺陷表面上的稳定性,计算了负载在Cu2O（111）完整表面和铜缺陷表面上的Pdn（n=1-4）对H2分子的最稳定吸附结构;利用在给定H2压力和温度下Pdn / Cu2O表面吸附H2的相图揭示了Pdn团簇在Cu2O（111）两个表面的变化情况。结果表明,在吸附了H2分子以后,Pdn团簇更倾向于保持原有的结构,且随着Pd团簇的增大,吸附H2的数量也逐渐增长。     

甲硫醇在Cu(111)表面的解离吸附: 密度泛函理论研究

采用基于密度泛函理论的第一性原理方法和平板模型研究了CH₃SH分子在Cu(111)表面的吸附反应.系统地计算了S原子在不同位置以不同方式吸附的一系列构型, 第一次得到未解离的CH₃SH分子在Cu(111)表面顶位上的稳定吸附构型,该构型吸附属于弱的化学吸附, 吸附能为0.39 eV. 计算同时发现在热力学上解离结构比未解离结构更加稳定. 解离的CH₃S吸附在桥位和中空位之间, 吸附能为0.75-0.77 eV. 计算分析了未解离吸附到解离吸附的两条反应路径, 最小能量路径的能垒为0.57 eV. 计算结果还表明S―H键断裂后的H原子并不是以H₂分子的形式从表面解吸附而是以与表面成键的形式存在. 通过比较S原子在独立的CH₃SH分子和吸附状态下的局域态密度, 发现S―H键断裂后S原子和表面的键合强于未断裂时S原子和表面的键合.     

DFT study of gas-phase adsorption of benzotriazole on Cu(111), Cu(100), Cu(110), and low coordinated defects thereon

The adsorption of benzotriazole--an outstanding corrosion inhibitor for copper--on Cu(111), Cu(100), Cu(110), and low coordinated defects thereon has been studied and characterized using density functional theory (DFT) calculations. We find that benzotriazole can either chemisorb in an upright geometry or physisorb with the molecular plane being nearly parallel to the surface. While the magnitude of chemisorption energy increases as passing from densely packed Cu(111) to more open surfaces and low coordinated defects, the physisorption energy is instead rather similar on all three low Miller index surfaces. It is pointed out that due to a large dipole moment of benzotriazole the dipole-dipole interactions are rather important. For perpendicular chemisorption modes the lateral repulsion is very long ranged, extending up to the nearest-neighbor distance of about 60 bohrs, whereas for parallel adsorption modes the lateral interactions are far less pronounced and the molecules experience a weak attraction at distances ?25 bohrs. The chemisorption energies were therefore extrapolated to zero coverage by a recently developed scheme and the resulting values are -0.60, -0.73, and -0.92 eV for Cu(111), Cu(100), and Cu(110), respectively, whereas the zero-coverage physisorption energy is about -0.7 eV irrespective of the surface plane. While the more densely packed surfaces are not reactive enough to interact with the molecular π-system, the reactivity of Cu(110) appears to be at the onset of such interaction, resulting in a very stable parallel adsorption structure with an adsorption energy of -1.3 eV that is ascribed as an apparent chemisorption+physisorption mode.     

2-氯噻吩在 Rh(111) 表面吸附的密度泛函理论研究

 采用密度泛函理论探讨了 2-氯噻吩分子在 Rh(111) 表面上吸附行为. 结果表明, 平行的 hol 位及 bridge 位上的吸附最稳定. 吸附后, 2-氯噻吩键长发生明显变化, 分子平面被扭曲, 分子中 C–H(Cl, S) 相对于金属表面倾斜上翘. 垂直吸附模式不如平行吸附模式稳定, 但吸附后噻吩环未发生变形. hol 及 bridge 吸附模式下 2-氯噻吩的芳香性已遭破坏, 噻吩环上的碳原子呈现准 sp3 杂化. 在平行的 hol 位吸附后, 2-氯噻吩环累计得到 0.77 个电子, 而 Rh(111) 表面累计失去 1.19 个电子.     

密度泛函理论研究十二烷硫醇在Au(111)面上的吸附

采用第一性原理方法研究了十二烷硫醇(C₁₂H₂₅SH)分子在Au(111)面上未解离和解离吸附的结构、能量和吸附性质,在此基础上分析判断长链硫醇分子在Au(111)面吸附时S―H键的解离, 以及分子链长度对吸附结构和能量的影响. 计算了S原子在不同位置以不同方式吸附的系列构型, 结果表明在S―H键解离前和解离后,均存在两种可能的表面结构, 直立吸附构型和平铺吸附构型; 未解离的C₁₂H₂₅SH分子倾向于吸附在top位, 吸附能为0.35-0.38 eV; H原子解离后C₁₂H₂₅S基团倾向于吸附在bri-fcc位, 吸附能量为2.01-2.09 eV. 比较分析未解离吸附和解离吸附, 发现C₁₂H₂₅SH分子未解离吸附相较于解离吸附要稳定, 未解离吸附属于弱化学吸附.局域电子态密度和差分电荷密度分析进一步验证了S―H解离后S原子与表面之间成键的数目增加, 而且键合更强. 同时我们发现长链硫醇的吸附能量较短链硫醇的吸附能量略大, S原子与表面Au原子之间的距离略小.     

α,β-不饱和醛在Ni-Pt(111)面上吸附的理论研究

利用密度泛函理论研究了巴豆醛和肉桂醛分子在Pt-Ni-Pt(111)面的吸附构型以及相关电子性质. 吸附构型与吸附能结果表明, 巴豆醛和肉桂醛在覆盖度为1/25 ML的条件下, 以C=C和C=O双键协同吸附在Pt-Ni-Pt(111)面较为稳定, 且肉桂醛与Pt-Ni-Pt(111)面的吸附能远大于巴豆醛. 由Mulliken电荷布局和差分电荷密度可知, 在吸附过程中肉桂醛分子向Pt-Ni-Pt(111)面上转移的电荷数较巴豆醛更多, 相互作用更大. 由电子态密度分析结果可知, 不饱和醛与Pt-Ni-Pt(111)面的吸附作用主要是由于分子的p轨道电子与催化剂d轨道电子之间的相互作用. 由于苯基的存在使肉桂醛分子在Pt-Ni-Pt(111)面上的吸附更强, 且平行于催化剂表面.     

Molecular anchor Cu-S formed on a thiophene mediated Si(111)-(7x7) surface

Thiophene molecule selectively binds to the adjacent adatom-rest atom pair on the Si(111)-(7x7) surface through its alpha-carbon atoms, leading to the covalent attachment of a C-S-C linkage and remaining C=C (beta-carbon) bond onto the surface. Photoemission studies show that Cu atom readily adsorbs onto the S atom of the functional group to form the Cu-S molecular anchor in two forms: one points away from the thiophene C=C group; the other points toward the C=C group.     

First-principles study on the reconstruction induced by the adsorption of C60 on Pt(111)

The adsorption of C60 on a Pt(111) surface and the origins of the √13 × √13R13.9° or 2√3 × 2√3R30° reconstruction of the C60/Pt(111) system have been investigated by means of first-principles calculations. In agreement with the experimental observations, our calculations reveal that the C60 molecule binds covalently on the Pt(111) surface. The C60 molecule adsorbs on the Pt(111) surface with the center of a hexagonal ring located on top of a surface Pt atom. The surface Pt atom can be removed easily, forming a Pt vacancy upon the adsorption of C60 molecule. Our calculation results show that the strong covalent bonds between C60 and the Pt(111) surface and the formation of adatom-vacancy pairs in the C60/Pt(111) system may be the main driving forces promoting the substrate reconstructing pattern observed in experiments.     

金属-有机配合物分子在Au(111)表面的吸附行为

用STM对含氧桥的金属-有机配合物[Cu₂(μ-O)(dptap)4(NO₃)₂]分子在Au(111)表面的吸附行为进行了研究. STM结果表明, 该分子同时存在非解离吸附和解离吸附, 大部分分子在Au(111)面形成有规则的排列, 少量分子发生解离吸附, 并形成(√3×√3)R30°Cu原子吸附结构. 探讨了两种吸附现象共存的起因.     

Complex orientational ordering of C60 molecules on Au(111)

The orientation and adsorption site for C(60) molecules on Au(111) has been studied using low temperature scanning tunneling microscopy. A complex orientational ordering has been observed for molecules inside the "in-phase" (R0°) domain. A 7-molecule cluster consisting a central molecule sitting atop of a gold atom and 6 tilted surrounding molecules is identified as the structural motif. The 2√3 × 2√3-R30° phase consists of molecules bonding to a gold atomic vacancies with a preferred azimuthal orientation. The quasi-periodic R14° phase is composed of groups of similarly oriented molecules with the groups organized into a 4√3 × 4√3-R30° like super-lattice unit cell.     

Conformation Controls Mobility: 2H-Tetranaphthylporphyrins on Cu(111)

The adsorption behavior and the mobility of 2H-Tetranaphthylporphyrin (2HTNP) on Cu(111) was investigated by scanning tunneling microscopy (STM) at room temperature (RT). The molecules adsorb, like the structurally related 2HTPP, in the “inverted” structure with the naphthyl plane restricted to an orientation parallel to the Cu surface. The orientation of the four naphthyl groups yields altogether 16 possible conformations. Due to the existence of rotamer pairs, 10 different appearances are expected on the surface, and all of them are identified by STM at RT. Most interestingly, the orientation of the naphthyl groups significantly influences the diffusion behavior of the molecules on Cu(111). We identify three different groups of conformers, which are either immobile, medium or fast diffusing at RT. The mobility seems to decrease with increasing size of the footprint of the conformers on the surface.     

Asymmetric Synthesis and Crystal Structure of （-）-N-[（3R）-3-Cyclohexyl]-3-phenylpropananoyl]bornane-10,2-sultam

The title compound (-)-N-[(3R)-3-cyclohexyl]-3-phenylpropananoyl]bornane-10,2sultam (C 25 H 35 NO 3 S,M r=429.60),a derivative of camphorsultam,crystallizes in the monoclinic space group P2 1 /c with a=10.3301(7),b=19.4040(13),c=11.8106(8),β=100.5580(10)°,V=2327.3(3) 3,Z=4,D c=1.226 g/cm 3,λ=0.71073,μ(MoKα)=0.165 mm-1 and F(000)=928.X-ray diffraction analysis reveals that the six-membered ring of sultam shows a boat form (Fig.1).The planes constructed by (C(4),C(5),C(6),C(7)) and (C(7),C(8),C(9),C(4)) form a dihedral angle of 69.5°.The C(1)-C(2)-C(3) plane forms dihedral angles to the aforementioned planes of 89.8(1) and 85.9(3)°,respectively.And molecules are linked via hydrogen bonding (C-H···N/O) interactions.     

Adsorption and coordination of tartaric acid enantiomers on Cu(111) in aqueous solution

Chiral modifiers have gained much attention because they can induce high enantioselectivity on reactive metal surface in heterogeneous enantioselective catalysis. The high enantioselectivity is attributed to that the chirality of modifiers is bestowed onto the metal surface upon adsorption. Much study on the adsorption of modifiers on metal surface has been performed in an ultrahigh vacuum. In this paper, the adsorption of tartaric acid on Cu(111) has been studied by electrochemical scanning tunneling microscopy (STM) in aqueous solution. It is found that (R,R)-tartaric acid and (S,S)-tartaric acid can form a well-ordered adlayer on the Cu(111) surface with a (4 x 4) symmetry. A dimeric structure is proposed in the temporary model from STM observation.     

Low-temperature adsorption of H2S on Ag(111)

H(2)S forms a rich variety of structures on Ag(111) at low temperature and submonolayer coverage. The molecules decorate step edges, exist as isolated entities on terraces, and aggregate into clusters and islands, under various conditions. One type of island exhibits a (√37×√37)R25.3° unit cell. Typically, molecules in the clusters and islands are separated by about 0.4 nm, the same as the S-S separation in crystalline H(2)S. Density functional theory indicates that hydrogen-bonded clusters contain two types of molecules. One is very similar to an isolated adsorbed H(2)S molecule, with both S-H bonds nearly parallel to the surface. The other has a S-H bond pointed toward the surface. The potential energy surface for adsorption and diffusion is very smooth.     

Imaging the Bonds of Dehalogenated Benzene Radicals on Cu(111) and Au(111)

Dissociative adsorption of doubly substituted benzene molecules leads to formation of benzyne radicals. In this study, co‐adsorbed hydrogen molecules are used in scanning tunneling hydrogen microscopy to enhance the contrast of the meta‐ and the para‐isomers of these radicals on Cu(111) and Au(111). Up to three hydrogen molecules are attached to one radical. One hydrogen molecule reveals the orientation of the carbon ring and its adsorption site, allowing discrimination between the two radicals. Two hydrogen molecules reflect the bond picture of the carbon skeleton and reveals that adsorption on Cu(111) distorts the meta‐ isomer differently from its gas‐phase distortion. Three hydrogen molecules allow us to determine the bond picture of a minor species.     

噻吩在M(111)(M=Pd,Pt,Au)表面的吸附(英文)

采用密度泛函理论(DFT),选取DMol3程序模块,对噻吩在M(111)(M=Pd,Pt,Au)表面上的吸附行为进行了探讨.通过对噻吩在不同底物金属上的吸附能、吸附构型、Mulliken电荷布居、差分电荷密度以及态密度的分析发现,噻吩在Pd(111)面上的吸附能最大,Pt(111)面次之,Au(111)面最小.吸附后,噻吩在Au(111)面上的构型几乎保持不变,最终通过S端倾斜吸附于top位;噻吩在Pd(111)及Pt(111)面上发生了折叠与变形,环中氢原子向上翘起,最终通过环平面平行吸附于hollow位.此外,噻吩环吸附后芳香性遭到了破坏,环中碳原子发生sp3杂化,同时电子逐渐由噻吩向M(111)面发生转移,M(111)面上的部分电子也反馈给了噻吩环中的空轨道,这种协同作用最终导致了噻吩分子稳定吸附于M(111)面.