Synthesis,X-ray crystal structure and electrochemical properties of (dithiolato)(diimine)copper(II) complexes: [Cu(mnt)(phen)] n and [Cu(dmit)(phen)] 2

Copper (II) complexes [Cu(dmit)(phen)]₂ (1) and [Cu(mnt)(phen)] _n (2) (mnt^2??=?maleonitriledithiolate, dmit^2??=?1,3-dithiole-2-thione-4,5-dithiolate, phen?=?1,10-phenanthroline) have been prepared by ligand-exchange between phen and [N(Bu)₄]₂[Cu(dmit)₂] or [N(Bu)₄]₂[Cu(mnt)₂]. Both complexes have been characterized by spectroscopic, electrochemical, and single-crystal X-ray analysis. In complex 1, dimers are extended into a two-dimensional array by weak S5–Cu contacts. In complex 2, monomers are extended into chains in a head-to-tail arrangement by weak Cu–S coordination bonds and π–π stacking interactions.     

cis-trans Germanium chains in the intermetallic compounds ALi1-xInxGe2 and A2(Li1-xInx)2Ge3 (A=Sr, Ba, Eu)—experimental and theoreticalstudies

Two types of strontium-, barium- and europium-containing germanides have been synthesized using high temperature reactions and characterized by single-crystal X-ray diffraction. All reported compounds also contain mixed-occupied Li and In atoms, resulting in quaternary phases with narrow homogeneity ranges. The first type comprises EuLi_0.91(1)In_0.09Ge₂, SrLi_0.95(1)In_0.05Ge₂ and BaLi_0.99(1)In_0.01Ge₂, which crystallize in the orthorhombic space group Pnma (BaLi_0.9Mg_0.1Si₂ structure type, Pearson code oP16). The lattice parameters are a=7.129(4)-7.405(4) Å; b=4.426(3)-4.638(2) Å; and c=11.462(7)-11.872(6) Å. The second type includes Eu₂Li_1.36(1)In_0.64Ge₃ and Sr₂Li_1.45(1)In_0.55Ge₃, which adopt the orthorhombic space group Cmcm (Ce₂Li₂Ge₃ structure type, Pearson code oC28) with lattice parameters a=4.534(2)-4.618(2) Å; b=19.347(8)-19.685(9) Å; and c=7.164(3)-7.260(3) Å. The polyanionic sub-structures in both cases feature one-dimensional Ge chains with alternating Ge-Ge bonds in cis- and trans-conformation. Theoretical studies using the tight-binding linear muffin-tin orbital (LMTO) method provide the rationale for optimizing the overall bonding by diminishing the π-p delocalization along the Ge chains, accounting for the experimentally confirmed substitution of Li forIn.     

Molecular assemblies of trichloride neodymium and europium complexes chelated by 1,10-phenanthroline

Four trichloride lanthanide (neodymium or europium) complexes (1-4) have been solvothermally synthesized with the 1,10-phenanthroline (phen) chelate in ethanol solvent and their structures have been characterized by single-crystal X-ray diffraction analysis. Depending on the Ln/phen ratio, different motif nuclearities have been observed. With Ln/phen = 1/2, a dinuclear species with μ₂-Cl₂ edge-sharing bridge is formed with neodymium, NdCl₃(phen)₂ (1), whereas a mononuclear complex appears with europium, EuCl₃(phen)₂ (4) with an unusual pentagonal bipyramid for the lanthanide center (coordination 7). When Ln/phen ratio increases (1/1), an identical complex is obtained with Nd (2) or Eu (3). It is a monohydrated complex LnCl₃(H₂O)(phen)₂ with one water molecule completing the coordination sphere of the lanthanide. For all compounds, each rare-earth cation is chelated by two distinct phen ligands. Thermal behavior of complexes 1 and 2 are discussed (by means of thermogravimetric analysis and X-ray thermodiffraction) as well as the luminescence spectra of europium-based complexes 3 and 4 (Supplementary Material).     

Epitactic formation of forsterite on MgO single crystals during vacuum annealing

Specimens of {0 0 1} MgO, prepared for analysis in the transmission electron microscope (TEM), have been heated in situ in a conventional TEM in order to study the effect of different heat treatments on the surface of the MgO specimens. A previous study, using a similar in situ heat treatment of MgO, found that at elevated temperatures (∼500 K) a film of different structure and composition formed on the surface of the sample. The previous study concluded that the composition and structure corresponded to that of MgO₂. In the present study, similar results to those shown previously have been found. However, the interpretation of these results is quite different. The films are shown to be of a composition and crystal structure that is consistent with forsterite, Mg₂SiO₄. The films can form as a result of contamination during the high-temperature in situ annealing process.     

Surface studies of supported model catalysts

Metal particles grown by vapour deposition on clean and well-defined oxide surfaces are used as model catalysts. These new model catalysts allow, unlike metal single crystals, a study of size and support effects in heterogeneous catalysis. The structure, the electronic properties and the reactivity of these supported model catalysts have been studied, in situ, by a large number of surface science techniques. In order to get relevant information from those studies it is necessary to control the nucleation and growth in order to get uniform collections of metal particles. The preparation conditions and the characterisation methods will be reviewed. Particles with well-defined shapes are obtained by epitaxial growth at high temperature on clean ordered surfaces. The electronic properties of the small metal particles depend not only on their size but also on their shape. The chemisorption properties are strongly related to the surface structure of the particles. The interplay between the surface structure, the local electronic properties and the adsorption energy will be discussed for CO chemisorption. The presence of the support plays an important role in the control of the particle morphology. Furthermore, it can increase the adsorption rate. The intrinsic heterogeneity of the supported model catalysts has to be taken into account to understand in detail the catalytic reactions. The reaction rate cannot be considered as an average on the different crystalline facets present on the particle. Finally, we will discuss the possibility to study in situ and at the atomic level simple chemical reactions on supported catalysts.     

Single-crystal analyses of a series of asymmetrically synthesized α-amino acid precursors

Three α-amino acid precursors and their common substrate were structurally analyzed by means of X-ray crystallography. Though the precursors were synthesized under asymmetric reaction conditions and showed certain optical activities, their single-crystals were in racemic forms. A systematic structural investigation on these precursors has been carried out by comparing their molecular conformations and crystal packing to that of the substrate.     

固态离子晶体β-K0.294Ga1.969O3的高压与变温拉曼光谱研究

β-镓酸盐（β-gallate）型化合物是一种非常有应用前景的固态离子导体,在储能领域具有重要的应用价值。该类型化合物导电层中往往可以容纳过量的碱金属离子,使得该体系体现出复杂的晶格动力学行为,这也为进一步理解其导电机制带来了困难。压力与温度两个参量均可以通过改变原子间的间距而影响材料的结构,在研究材料的动力学过程,尤其在研究离子的扩散过程方面有很大的应用价值。迄今为止,对于温度依赖的β-镓酸盐型化合物的特性研究很少,且尚无β-镓酸盐型结构化合物的高压研究。由于激光拉曼散射技术在研究物质晶格动力学方面的独特优势,尤其压力与温度依赖的拉曼光谱可以提供重要的结构信息,是研究物质晶格动力学行为的有效实验手段。使用大腔体静高压技术成功合成了一种新型的β-镓酸盐型K_0.294Ga_1.969O₃(KGO)晶体,利用扫描电镜、能谱对晶体进行了表征,通过单晶X射线衍射对其晶体结构进行了解析,并与β-Ga₂O₃的晶体结构进行了对比分析。利用高压和变温拉曼光谱研究了KGO导电层中无序碱金属离子的晶格动力学行为。研究发现,由尖晶石层与疏松的离子导电层交替排列而成的β-镓酸盐型KGO晶体结构在压力23.3 GPa条件下仍可保持稳定;由于振动模式不同,高频拉曼模与低频拉曼模的压力系数存在着显著差异,并表现出显著的对压力诱导非谐性。在约300 ℃,KGO中K+发生热激活,表现在与碱金属K+运动相关的低频拉曼模的强度迅速增加,而与Ga-O多面体相关的高频振动模强度增加缓慢,与此同时,K+在沿着导电平面的方向上发生了无序扩散过程。研究结果将有助于深入地理解β-镓酸盐型结构化合物的导电机制,而且对于实现β-镓酸盐型化合物精确的计算控制和掺杂尤为重要。     

Synthesis and characterization of the pseudo-hexagonal hollandites ALi2Ru6O12 (A=Na, K)

The crystal structures, synthesis and physical properties of ruthenium hollandites ALi₂Ru₆O₁₂ (A=Na, K) with a new pseudo-hexagonal structure type are described. Analogous to tetragonal hollandites, the framework is made of MO₆ octahedra in double chains that share corner oxygens with each other to create interstitial tunnels. The tunnels are either hexagonal or triangular in cross-section. Magnetic susceptibilities, low temperature specific heat, and electrical resistivities are reported. The data indicate that these materials are normal, low density of states metals. This new structure type can be extended from A=Group I to A=Group II ions with the synthesis of CaLi₂Ru₆O₁₂ and SrLi₂Ru₆O₁₂.     

Empty electronic states in low-energy absorbed current spectroscopy of NbSe2(0 0 0 1) surface

The fine structure of the experimental absorbed current spectra along the normal to a clean NbSe₂(0 0 0 1) surface is interpreted theoretically. It is shown that the fine structure of absorbed current spectra is mainly due to the electronic structure of unoccupied high-level electronic states (above the vacuum level), which become occupied by electrons entering a solid. The predominant role of the bulk energy-band structure effects in the spectra formation is shown. In addition, a comparison to existing theoretical and experimental data is given.     

An atypical easy reductive cleavage of the conjugated CC bond in 1,1′-disubstituted isoindigos under the action of aqueous hydrazine hydrate

The reaction of diverse symmetrically-substituted isoindigo derivatives with 80% aqueous hydrazine hydrate is described. The influence of the structure of the substituent on either oxindole or isatin-3-hydrazone formation is discussed.