Infrared and MAS NMR Spectroscopic Studies of Al18B4O33

IntroductionAllsB.O,, is a refractory compound with the melting point of 1 713 K. It has a low density of 2. 94 g/cm' and tends to form a needle--shaped crystal. These characteristics lead to itspotential application in reinforced plastics or metal alloys['j. The investigationL'] in the crystalstructure Of Al,SB,O,, by X-ray study has reve.aled that the material has a 10Al,O,. BZO3type structure. This structure contains AIO.--tetrahedra, AIO,-octahedra, five-oxygen-coordinated Al ato…     

成庄无烟煤大分子结构模型及其分子模拟

利用晋城矿区成庄矿煤的工业分析、元素分析、¹³C-NMR、XPS等实验结果,构建了其大分子结构模型.模型中,芳香碳以2、3、4环结构为主,最大环数达五个;脂肪碳以甲、乙基侧链及环烷烃的形式存在.九个氧原子分别以七个羰基(主要为醌基)、一个羟基及一个醚氧的型式存在;两个氮原子以吡咯的形式存在.硫原子含量很低,在模型构建中没有体现.采用分子力学(MM)和分子动力学(MD)方法,对成庄煤结构模型进行能量最小化模拟.结果表明,分子内及分子间芳香层片之间的π-π相互作用,使其以近似平行的方式排列;高煤级煤结构中,短程有序的原因主要是分子间芳香层片的定向排列.分子间的氢键能及范德华能使结构达到最稳构型.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. XXXIX. Blei(II)-bis-tri-tert-butoxysilanthiolat

Contributions to the Chemistry of Silicon Sulfur Compounds. XXXIX. Lead(II)-bis-tritertbutoxysilanethiolate The title compound 1 is formed from (t-C₄H₉O)₃SiSH and PbO by an exothermic reaction. In benzene solution 1 is monomeric, whereas a solvated dimer the structure of which was determined crystallizes from glyme solutions. The F.I. mass spectrum only shows the mass of the monomeric unit. The ²⁹Si n.m.r. spectrum shows only one sharp signal at δ = ?68.33 ppm. The central four-membered (Pb₂S₂) ring of the dimer is puckered (butterfly; 51.2°). The folding takes place at the Pb atoms. The Pb atoms are threefold coordinated by S atoms (d_endo = 278.9 pm; d_exo = 258.6 pm) whereas the S atoms are bonded to two Pb atoms and one Si atom (208.8–214.3 pm).     

Ab initio and experimental study of the K-shell spectra of 2,5-dihydrofuran

The K-shell spectra of gaseous 2,5-dihydrofuran at the carbon and oxygen thresholds are reported for the first time. They have been measured using the inner-shell electron energy loss spectroscopy (ISEELS) method. Ab initio Configuration Interaction calculations have been carried out to assign the observed bands. The O1s spectrum is similar to that of tetrahydrofuran and the assignments of the bands are close to those obtained in the case of furan, excepting the furan first π* band. At the C1s edge, the spectrum differs from the furan case, because of the different chemical environment of one of the non-equivalent carbon atoms: due to the presence of hydrogen atoms out of the carbon–oxygen ring plane, several Rydberg core excited states have an important valence character, leading to large intensities in the experimental spectrum.     

铕与2，4-二氯苯甲酸一维链状配位聚合物的合成，晶体结构和发光性质

溶液法合成了一个新的铕配位聚合物[Eu(2,4-DClBA)₃(CH₃CH₂OH)₂]_n(2,4-DClBA=2,4-二氯苯甲酸根),并用X-射线单晶衍射分析确定了其晶体结构。配合物晶体属于三斜晶系,P1空间群。标题配合物是无限一维链状聚合物,中心Eu³⁺离子通过桥联双齿2,4-二氯苯甲酸根氧原子连接。Eu³⁺离子的配位数为8     

一维链状4-乙基苯甲酸镧配合物[La(EBA)_3(EBAH)(H_2O)]_n的合成、晶体结构和性质研究(英文)

水热法合成了配位聚合物[La(EBA)3(EBAH)(H2O)]n(EBA=4-乙基苯甲酸根,EBAH=4-乙基苯甲酸),并通过X-射线衍射单晶结构分析、红外光谱、紫外光谱、荧光光谱以及热重分析对配合物进行了结构和性质研究。配合物属三斜晶系,P1空间群。该配合物具有一维链状结构。La3+离子与9个O原子配位,其中4个O原子来自4个双齿桥联的4-乙基苯甲酸根,3个O原子来自2个螯合-桥联的4-乙基苯甲酸根,1个O原子来自1个中性的4-乙基苯甲酸,1个O原子来自配位水分子。La3+离子处于九配位扭变的三帽三角棱柱构型中。相邻La3+离子通过双齿桥联或螯合桥联的4-乙基苯甲酸根联结成一维链状结构。存在于分子内的氢键使一维链状结构更加稳定。由于相邻一维链的苯环间存在弱的π…π堆积作用,使分子沿着a轴堆积形成二维层状结构。同时,标题配合物固体具有光致发光特性,蓝光区的较强发射归于配体的π→π*电子跃迁。     

g-C3N4碳位掺杂电学及光学性质的分析

使用第一性原理研究了C位掺杂的g-C₃N₄的电学性质和光学性质,掺杂原子为B、P、S. g-C₃N₄有C1位和C2 位两种对称位碳原子,其中在C1 位上的掺杂易于C2 位,掺杂体系也较C2 位稳定. 相比于磷和硫在g-C₃N₄上的掺杂,硼掺杂最易于进行. 掺杂后体系的晶体结构之间差别较大,这与掺杂原子的大小以及电负性有关. 由轨道布居分布可知,掺杂后的硼、磷、硫原子价电子发生了变化,表明掺杂原子发生了杂化,与相邻原子以强的共价键相连. 掺杂原子与被取代的碳原子之间的价电子差异导致了能带的增加. 在原来的体系中,掺杂后的体系出现了一条新的能带,因此导致实际带隙下降,表明了掺杂后的体系导电性能增强. 对纯g-C₃N₄及掺杂g-C₃N₄的光学性质分析表明,g-C₃N₄的光学吸收主要在紫外光区,掺杂磷和硫后对g-C₃N₄的光吸收波长范围无改变,掺杂硼后的g-C₃N₄光吸收不再局限于紫外光区,而且延伸至可见光区和红外光区,并在红外光区有很强的吸收,表明g-C₃N₄掺杂硼后能大大地提高光催化效率. 电子能量损失光谱和光导率谱以及介电常数都佐证了上述观点.     

Complete assignment of the carbon-13 NMR spectrum of chlorophyl a

The ¹³C NMR spectrum (at natural abundance) of monomeric chlorophyll α in acetone-d₆ has been recorded to re-examine the assignments of the low field (aromatic-olefinic) region of the spectrum. The assignments, made by the examination of the fully coupled spectrum and by the use of long-range selective ¹H decoupling (LSPD) with low-power irradiation, were compared with those of the previous reports. The results of the present work clarify the ambiguities previously encountered in the assignment of the 10a-ester, 7c-propionyl, P-2-phytyl, 2b-vinyl, γ- and β-methine carbon atoms, as well as the β-pyrrolic carbon-6 and α-pyrrolic carbons ?16 and ?17 of chlorophyll α. Reassignment of the three last carbons was found necessary. Knowledge of the chemical shifts of these carbon atoms was considered to be particularly valuable, as it yields relevant information on the delocalized π electron system which is crucial for the function of chlorophyll in photosynthesis.     

Low-frequency (20–400 cm−1) vibrational spectra of N-methylacetamide in the liquid state

Low-frequency Raman spectra (20–400 cm⁻¹) of liquid N-methylacetamide were studied. The experimental data were directly transformed into the R(v) representation. This spectrum was compared with the far infrared spectrum. Temperatures from 30 to 165 °C were investigated. A low-frequency band around 100 cm⁻¹ is assigned to a mode involving atoms in intermolecular hydrogen bonds. This assignment is qualitatively supported by the observed spectrum of Nd-methylacetamide.     

Analysis of the LIF Spectroscopy of Nickel Hydride in 19000-21400 cm-1

The laser-induced fluorescence (LIF) excitation spectrum of NiH was recorded in the spectral region from 15000 cm-1 to 21400 cm-1, with the NiH molecules produced by the reaction of sputtered nickel atoms with methanol under supersonic jet conditions. The 19000-21400 cm-1 portion of the spectrum of NiH is reported for the first time. Twenty-four bands were observed and classified into seven electronic transitions. Every band was rotationally analyzed. Higher vibrational levels of many excited states, A, B, D, E, F, and G,were observed and the complete set of spectroscopic parameters, vibrational frequency, unharmonic constant, rotational constant, and equilibrium length of these states were obtained. Some bands were reassigned     

一维链状3-碘苯甲酸铽配合物的合成、晶体结构和性质表征

溶液法合成了配合物{[Tb(3-IBA)₃(H₂O)₂]·0.5(4,4′-bipy)}_n(3-IBA=3-碘苯甲酸根;4,4′-bipy=4,4′-联吡啶),并通过X-射线衍射单晶结构分析、红外光谱、紫外光谱、荧光光谱以及热重分析对配合物进行了结构和性质表征。配合物晶体属三斜晶系,P1空间群。该配合物具有一维链状结构。Tb³⁺离子与8个O原子配位,其中6个O原子来自5个3-碘苯甲酸根,2个O原子来自水分子。相邻Tb³⁺离子通过2个双齿桥联的3-碘苯甲酸根联结成一维链状结构。未配位的4,4′-联吡啶分子与配位水分子之间形成氢键,并将相邻的一维链联结起来形成二维网状结构。沿a轴的分子堆积形成一维孔道,是由于相邻一维链的苯环之间部分重叠而形成的。在紫外光照射下,配合物发出很强的绿色荧光。配合物的荧光光谱中,4个峰位于490、544、583和619 nm,分别对应于Tb³⁺离子的⁵D₄→⁷F₆、⁵D₄→⁷F₅、⁵D₄→⁷F₄和⁵D₄→⁷F₃跃迁。     

取向Zn1-xMgxO纳米线阵列的制备及光学特性

采用化学气相沉积(CVD)法, 以高纯ZnO、Mg和活性C混合粉末为原料, 在Si(111)衬底上制备了不同配比的取向Zn1-xMgxO纳米线阵列. 用X射线衍射仪(XRD), 扫描电镜(SEM), 能量色散X射线分析(EDAX)及光致发光(PL)光谱分析仪对样品的晶体结构、形貌、成分组成和光致发光特性进行了分析. 用霍尔效应测量系统测试了不同配比样品的载流子浓度. 实验发现, 当Zn1-xMgxO纳米线阵列中Mg原子相对Zn原子摩尔比x值较小时(x<0.29), XRD衍射谱中只有ZnO晶体标准衍射峰, 没有MgO晶体衍射峰, 说明此时制备的Zn1-xMgxO纳米线样品晶格结构以ZnO纤锌矿结构为主, Mg原子只是作为替位或填隙原子分布在ZnO晶体中. 但当样品中x>0.53时, ZnO与MgO的特征衍射峰同时出现在样品的衍射谱图中, 说明随原料中Mg原子摩尔比的增加, 制备的Zn1-xMgxO纳米阵列样品中ZnO纤锌矿结构与MgO岩盐结构同时存在, 样品呈现多晶体结构形式. 实验还对比了制备的纯ZnO与不同配比的Zn1-xMgxO纳米线阵列的光致发光光谱和载流子浓度, 发现随Mg含量的增加, Zn1-xMgxO阵列紫光发光峰出现了较明显的蓝移现象, 同时, 测试结果也表明, 随Mg含量的增加, Zn1-xMgxO阵列的紫光和绿光峰发光强度都有所减弱, 样品的载流子浓度也随之下降. 文章对实验结果进行了分析和探讨.     

Synthesis and spectroscopic studies of the new Ag(I) organoselenium complex

The new complex of Ag(I) with an organoselenium compound was synthesized. The 2 : 1 (silver : ligand) stoichiometry of the complex and chelating mode of the hetero-selenium ligand have been considered on the basis of elemental analyses, IR, Raman, ¹H and ¹³C NMR, and thermogravimetric data. The IR spectrum of the complex supported two sites of coordination (selenium and nitrogen atoms of quinoline moiety). The bidentate ligand was bound to selenium via oxygen atoms of the carboxylate group. The complex demonstrated the non-electrolyte nature. Nano-scale range of Ag(I) complex has been estimated according to X-ray powder diffraction, scanning electron microscope and transmission electron microscopy.     

N-氧化吡啶-2-甲醛衍生物的配合物研究 III: N-氧化吡啶 -2-甲醛缩氨基硫脲的双核铜配合物的晶体结构和电子结构

合成了N-氧化吡啶 -2-甲醛缩氨基硫脲的双核铜配合物。晶体结构的测定表明两Cu原子之间是通过两个单原子氧桥相联, 每个桥联氧原子既处于一个Cu原子为中心的四方锥底面, 又是另一个Cu原子四方锥的锥顶。晶体属单斜晶系, 空间群为Ce, 晶体结构参数为a=16.445,b=13.889,c=12.770A,β=122.82°。根据半经验MO法的计算结果, 指出了红外谱中N-O键和C=N 键特征峰朝不同方向位移的原因, 并对磁偶合常数作了估计。     

Monte Carlo simulations of Na atoms in dynamically disordered Ar systems: Solid,liquid, and critical-point fluid Ar

We present the results of simulations of the structures and optical absorption spectra of Na atoms in solid and liquid Ar at its triple point, and in critical-point Ar fluid. The spectral simulations combine a classical Monte Carlo scheme for generating thermally accessible ground state configurations, along with a first-order perturbation theory treatment of the interactions between the excited Na^*(3p ²P) atom and the surrounding Ar perturbers [Boatz and Fajardo, J. Chem. Phys., 101 , 3472 (1994)]. These simulations predict a “triplet” (i.e., three peaks) absorption lineshape for Na atoms in solid and liquid Ar at its triple point, and an asymmetrical, blue degraded absorption band for Na atoms in critical Ar fluid. We also note and discuss the similarities between the simulated Na/Ar₍₁₎ lineshape and an experimental Li/Ar/Xe mixed host matrix spectrum, and the similarities between the simulated spectrum of Na atoms in critical point Ar fluid, and an experimental Li/H₂ matrix absorption spectrum. © 1997 by John Wiley & Sons, Inc.     

Photoinduced charge transfer reaction at surfaces. III. (HF)2...Na n/LiF(001)+hnu(640 nm)-->HFF-Na n +/LiF(001)+H(g)

A sub-monolayer of atomic sodium was deposited on a LiF(001) surface at 40 K. The adsorbed sodium exists at the surface as single atoms and clusters. The surface was dosed with 1 L of HF, to form adsorbed (HF)2...Na(n) (n=1,2,3,...) complexes, which were then irradiated by 640 nm laser light, to induce charge-transfer reaction. The reaction-product atomic H(g) was observed leaving the surface by two-color Rydberg-atom time-of-flight (TOF) spectroscopy. The TOF spectrum of the desorbed H atoms contained two components; a "fast" component with a maximum at approximately 0.85 eV, and a "slow" component with a maximum at 0.45 eV. These two components were attributed to photoreaction on adsorbed single atoms and clusters of sodium, respectively. The fast component exhibited a structure (48+/-17 meV spacing) near the high-energy end of spectrum. This structure was attributed to vibration of NaFHF photoproduct residing on the surface. The cross section of the harpooning event in the Na...(HF)2 adsorbed complex was determined as (9.1+/-2.0)x10(-19) cm(2). To interpret the experimental vibrational structure and the relative energies of the fast and slow components of the TOF spectrum, high-level ab initio calculations were performed for reactants Na(n)...(HF)(m) (n,m=1,2) and reaction products Na(n)F(m)H(m-1). The calculated NaF-HF and Na-Na(HF)(2) bond dissociation energies indicated that photoexcitation of the precursor complexes led not only to ejection of H atoms, but also to dissociation of the Na(n)...(HF)(2) (n=1,2) species through cleavage of the NaF-HF and Na-Na(HF)(2) bonds.     

Phase transitions and critical phenomena of tiny grains carbon films synthesized in microwave-based vapor deposition system

Different peak trends of tiny grains carbon film have been observed under the investigations of the Raman spectroscopy and energy loss spectroscopy. Carbon films known in nanocrystalline and ultrananocrystalline diamond films are synthesized by employing microwave-based vapor deposition system. Carbon atoms exhibit several state behaviors depending on the incurred positions of their electrons. Different morphology of tiny grains under different chamber pressure is related to different rate of arriving typical energies at/near substrate surface. Those tiny grains of carbon film, which evolved in graphitic state atoms are converted to structure of smooth elements where elongation of atoms of one-dimensional arrays is as per exerting surface format forces along opposite poles from their centers. Such tiny grains in the film are the cause of v₁ peak under the investigation of the Raman spectrum because of the enhanced propagation of input laser signals through channelized inter-state electron gaps of elongated graphitic state atoms. Those tiny grains of carbon film, which evolved in fullerene state are the cause of v₂ peak. The tiny grains related to v₁ peak possess a low intensity as compared with the ones which comprised atoms having state behaviors known in their exceptional hardness. Tiny grains representing v₁ peak in the Raman spectrum are also the cause of field emission characteristic of a carbon film. Different peak recordings were made for the Raman at defined positions indicating a different state of carbon atoms for a different phase of deposited tiny grains, which is in line to their energy loss spectroscopy.     

Single crystal X-Ray structure of BeF2: α-quartz

We report for the first time, the synthesis and X-ray diffraction studies of single crystals of BeF(2). The crystals were obtained during the sublimation of amorphous BeF(2) under static reduced pressure. BeF(2) crystallizes in the chiral trigonal space group P3(1)21. A single-crystal X-ray diffraction study on these crystals shows that each of the Be atoms is bonded to four F atoms, and each of the F atoms is bonded to two Be atoms with associated Be-F bond distances of 1.5420(13) and 1.5471(13) ?, showing an almost regular tetrahedron. The infrared spectrum of these crystals recorded at room temperature shows distinct peaks around 770 and 410 cm(-1).     

具有方石英拓扑结构的微孔硫代锗锌酸盐的溶剂热合成与表征

微孔化合物是一类重要的材料,广泛地应用于催化、吸附及分离等领域。目前已知的微孔材料绝大多数为无机氧化物或氟氧化物,20世纪80年代末,Bedard等首先报道了微孔硫属化物的合成．这类化合物除具有微孔材料的性质外,还具有半导体性质,在电催化、光催化、太阳能电池及新型光电子材料如量子点(dots)及反量子点(antidots)材料方面有着广泛的应用前景,     

X-ray emission spectroscopy and electronic structure of heterocyclic compounds. 1. Furan

The electronic structure of the furan molecule was investigated by x-ray spectroscopy. A quantum-chemical calculation (ab initio) was undertaken, and the results were compared with the experimental data. The interpretation of the x-ray spectra of the molecule, the carbon atoms of which have a different energy position for the 1s levels, is discussed in detail. The electronic transitions from the MO to these core levels are clearly recorded in the carbon x-ray spectrum. It was shown experimentally that the HOMO is an orbital in which the electron density is localized at the carbon atoms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1631–1635, December, 1991.