Transitional Metal/Chalcogen Dependant Interactions of Hairpin DNA with Transition Metal Dichalcogenides,MX2

Owing to the attractive properties that transition metal dichalcogenides (TMDs) display, they have found recent application in the fabrication of biosensing devices. These devices involve the immobilization of a recognition element such as DNA onto the surface of TMDs. Therefore, it is imperative to examine the interactions between TMDs and DNA. Herein, we explore the effect of different transition metals (Mo and W) and chalcogens (S and Se) on the interactions between hairpin DNA and TMDs of both bulk and t‐BuLi exfoliated forms. We discovered that the interactions are strongly dependent on the metal/chalcogen composition in TMDs.     

Preparation and Crystal Growth of Transition Metal Dichalcogenides

Dichalcogenides are known from almost all transition metals. The representatives of this class of compounds show a number of interesting physical and chemical properties depending on their constituent transition metal and crystal structure, which makes them interesting for basic studies and applications in high-end electronics, spintronics, optoelectronics, energy storage, flexible electronics, DNA sequencing and personalized medicine to this day. Many of these properties and effects can only be investigated on chemically and crystallographically pure samples - usually on single crystals. The vast majority of these compounds can be crystallized using chemical vapour transport. However crystallization from the melt is also possible in a considerable number of compounds, including the frequently used self-flux technique. For several compounds the crystallization from different solvents or solvent mixtures by means of solvothermal or hydrothermal synthesis is described.     

Crystal chemistry of MX · MgX2 · 6H2O type compounds

The following MX · MgX₂ · 6H₂O compounds (double salt hexahydrates) were synthesized by variation of the M⁺ and X^? ions: CsCl · MgCl₂ · 6 H₂O, Li(H₂O)Cl · MgCl₂ · 6H₂O, NH₄Br · MgBr₂ · 6 H₂O, RbBr · MgBr₂ · 6 H₂O, CsBr. MgBr₂ · 6 H₂O, KI · MgI₂ · 6 H₂O, NH₄I. Mgl₂ · 6 H₂O and RbI · MgI₂ · 6H₂O. By X-ray analysis of powder samples the lattice parameters and the space group were determined. On the basis of the results thus obtained, an identification with structural types was carried out. In accordance with the findings, the structure is made up of (M⁺)X₆^?octahedra which are linked into perovskite type units by sharing vertices. Their interstices are occupied by the Mg(H₂O)₆²⁺ octahedra. A “tolerance factor” t which has been calculated on the basis of the proportion of radii and which attains values between 1.045 and 1.061 is a criterion for the upper limit of the area of existence of this structure. Carnallite has a higher to value and, therefore, a different structure.     

2D Transition Metal Dichalcogenides for Photocatalysis

Two-dimensional (2D) transition metal dichalcogenides (TMDs), a rising star in the post-graphene era, are fundamentally and technologically intriguing for photocatalysis. Their extraordinary electronic, optical, and chemical properties endow them as promising materials for effectively harvesting light and catalyzing the redox reaction in photocatalysis. Here, we present a tutorial-style review of the field of 2D TMDs for photocatalysis to educate researchers (especially the new-comers), which begins with a brief introduction of the fundamentals of 2D TMDs and photocatalysis along with the synthesis of this type of material, then look deeply into the merits of 2D TMDs as co-catalysts and active photocatalysts, followed by an overview of the challenges and corresponding strategies of 2D TMDs for photocatalysis, and finally look ahead this topic.     

Chemistry and Crystal Growth

Single-crystal materials, along with other forms of condensed matter (ceramics, polymers, liquid crystals, etc.) are fundamental to modern technology. The basic research and production of new materials with “tailored” solid-state physical properties therefore necessitate not only chemical synthesis but also the production of single crystals of a particular morphology (either bulk or thin layer crystals) and well-defined crystal defects (doping). In this review, an attempt is made to broaden the traditional synthetic concept of chemistry to the process of single-crystal synthesis. The methods of the resulting approach, which takes into account the specific properties of solid materials, are discussed and illustrated by experimental set-ups for the solution of a range of problems in chemical crystallization. Also included is recent work on the growing of single crystals of high-temperature superconductors, organic non-linear optical compounds, and proteins.     

Crystal Chemistry of Rare-Earth Chalcogenides

Crystal structures of Ln–X, Ln–Ln'–X, Ln–M–X, and Ln–X–Z compounds (Ln and Ln' are rare-earth elements; M is subgroup I–VIIIa or II–Vb cation and Z is subgroup V–VIIb anion; X is S, Se, or Te) were systematized and analyzed using data obtained by us and data from the literature. The structures of binary Ln–X chalcogenides can be divided into 4 groups: derivatives of NaCl-type structures, structures with one small parameter b 4 Å, structures similar to those of oxides and pniktides, and derivatives of PbFCl-type structures. Triple Ln–Ln'–X chalcogenides have structures similar to those of the binary chalcogenides of the first, second, and third groups. It was shown that the crystal structure of Ln–M–X depends on the size of cation M, its formal charge, electronegativity value, and electronic structure. The crystal structures of the phases in the Ln–M–X and Ln–X–Z compounds were compared with binary chalcogenide structures. Different variants of structure characterization and their potentialities are considered. Special attention is given to the defect-containing and ordered structures and to elucidating the role of the cation and anion vacancies in the phase structures.     

晶体化学中的次级键

应用现代实验技术精确测定分子和晶体的微观结构是 2 0世纪自然科学的一项伟大成就。主要基于晶体结构数据归纳出来的 4套半径数据 ,即离子半径、共价半径、金属原子半径和范德华半径构成了结构化学的支柱。人们利用其各自具有的恒定性和加和性研究物质的结构以及结构与性能的关系 ,已经取得了丰硕的成果。　　离子键、共价键和金属键是化学键的极限类型。不同化学键型之间的过渡所形成的相对于极限键型的偏离被称为键型的变异 ,但是化学键与范德华引力是原子间作用力的不同层次。除后者无须电子云重迭因而没有方向性和饱和性外 ,其作用能要…     

The Crystal Chemistry of Copper Oxometalates

Up to three or four years ago oxocuprates were a class of chemical compounds no more remarkable than countless others. Then, as a result of the euphoria surrounding the high-temperature oxide superconductors and the discovery that copper plays an essential role in these materials, there was a world-wide awakening of interest in copper-containing oxide compounds. The number of scientists engaged in the synthesis and structure determination of copper oxometalates has grown from just a few to very many. As superconductivity is inseparably connected with the structure of the solid state, there has been a spontaneous awakening of interest in the role of copper in the crystal chemistry of solid materials, leading to new research projects on this aspect of oxocuprates. Most of the work published so far on the interesting chemistry of this group of compounds has related to individual compounds. New aids in describing complex solid state structures are now available through the development of methods that give three-dimensional displays of crystal structures using computer graphics terminals, as this review illustrates for the example of the oxocuprates.     

The Crystal Structure of Ba2Cu2AlF11: a New Structure Type in Copper Fluoride Crystal Chemistry

Ba₂Cu₂AlF₁₁ is trigonal: a = 7.301(1) Å, c = 14.145(2) Å, γ = 120°, Z = 3. The crystal structure was solved in the space group P3₂ (n° 145), from X-ray single crystal data using 2675 unique reflections (2476 with F/σ(F) > 4). It consists in a complex tridimensional arrangement of copper-fluorine and aluminium-fluorine octahedra, with an original kind of linkage which involves simultaneously edges and vertices.     

两个有机锡呋喃-2-甲酸酯化合物的合成、结构及量子化学研究

氧化双[三(2-甲基-2-苯基)丙基锡]、三苄基氯化锡分别与呋喃-2-甲酸反应,合成了配位聚合物{[(C4H3O)CO2]Sn(CH2CPhMe2)3}n(1)和{[(C4H3O)CO2]Sn(CH2Ph)3}n(2)。经IR、1H NMR、元素分析和X射线衍射表征结构。1和2均属单斜晶系,配合物1空间群P21/n,晶体学参数:a=1.122 06(7)nm,b=1.747 60(11)nm,c=1.632 62(10)nm,β=91.503(3)°,Z=4,V=3.200 3(3)nm3,Dc=1.306 g.cm-3,μ(Mo Kα)=0.829 mm-1,F(000)=1 304,R1=0.023 9,wR2=0.059 4。配合物2空间群C2/c,晶体学参数:a=2.939 49(13)nm,b=1.035 36(4)nm,c=1.976 64(9)nm,β=129.582(2)°,Z=8,V=4.636 4(3)nm3,Dc=1.442 g.cm-3,μ(Mo Kα)=1.125 mm-1,F(000)=2 032,R1=0.024 2,wR2=0.060 6。配合物1和2的中心锡原子分别为四面体和三角双锥构型。通过分子间氢键作用,1和2分别形成三维结构。对配合物进行了量子化学从头计算,探讨了配合物的稳定性、分子轨道能量及一些前沿分子轨道的组成特征。     

晶体工程及其在化学中的应用

晶体工程是实现分子到材料的一条重要途径 ,化学家致力于晶体工程是为了更好了解分子间的相互作用以便设计新颖的固体材料及固体反应     

富铁硅钛铈矿的晶体化学

通过电子探针分析和晶体结构测定, 证明四川冕宁碱性花岗岩中的天然非变生铁硅钛铈矿, 以富含铁、稀土和铌为特征, FeO(全铁)质量分数为10.97%～11.59%, Ce2O3 变化范围为23%～25%, Nb2O5为1.53%～2.10%;化学式中存在A型和(B C)型阳离子缺失; 具有C2/m空间群(R=2.41%); 晶胞参数为: a=1.3456(3) nm, b=0.57280(10) nm, c=1.1083(2) nm, β=100.60(3)°, V=0.8397(3) nm3, Z=2. 富铁硅钛铈矿的晶体结构由2种层组成, 一是由Si2O7 基团和B-八面体构成的层, 一是由C-八面体层构成的层; 2种层均平行ab平面, 沿c轴交替排列构成三维格架. 稀土离子位于双硅酸根和八面体层之间, 形成(8 3)配位的A(1)多面体和10配位的A(2)多面体. Fe和Ti呈部分有序分布于B, C(1), C(2A) 和C(2B)位置中.     

Crystal Chemistry of Complex Carbides and Related Compounds

Numerous metal carbides can be discussed in a rather uniform way by means of structural features, mainly characterized by the mode of linking of octahedral and occasionally trigonal prismatic [M₆C] groups (M = transition element). From this point of view perovskite carbides (M₃M′C, M′ = another transition or A-group element) and derivatives, β-Mn carbides (M₃M′₂C), κ-carbides, carbides with V₃AsC- and Cr₂AlC type structures and derivatives, η-carbides (M₃M′₃C) and carbides having the filled Mn₅Si₃ type structure will be treated. The high stability of these complex carbides is due to the strong bonding M? C and additional bonding of M? M′ atoms forming an ordered parent lattice. Besides the interstitial principle of filling of lattice holes (by isolated carbon atoms), substitution with A-group elements may also take place. Thus in borocarbides extended structural elements occur.     

In Situ Hydrogenation and Crystal Chemistry Studies of Co2Si Type Compounds MgPd2 and Pd2Zn

The hydrogenation properties of the intermetallic compounds MgPd₂ and Pd₂Zn, crystallizing in the Co₂Si type, were studied by in situ thermal analysis (DSC) under hydrogen pressure. Pd₂Zn does not show any reaction with hydrogen while MgPd₂ reversibly forms the hydride MgPd₂H. Neutron diffraction on the deuterides reveals the compositions MgPd₂D_0.861(6) (ambient) and MgPd₂D_0.97(1) [308(2) K, 2.56(5) MPa deuterium] with hydrogen (deuterium) occupying distorted [MgPd₅] octahedral voids. Quantum mechanical calculations support the structure models and show the hydrogenation to be exergonic for MgPd₂ and endergonic for Pd₂Zn. MgPd₂H releases hydrogen under normal conditions or vacuum. Heating under hydrogen pressure leads first reversibly to MgPd₂H_≈0.2 and subsequently irreversibly to MgPd₃H_≈1 and MgH₂. MgPd₂, Pd₂Zn, and MgPd₂H were classified in a structure map. Trends of axial ratio changes upon hydrogenation of TiNiSi type and ZrBeSi type compounds are discussed.     

三环已基锡2-氨基-6-氯苯甲酸酯配合物的合成、结构及量子化学研究

三环己基氢氧化锡与2-氨基-6-氯苯甲酸按物质的量比1∶1在苯溶剂中反应合成了三环己基锡2-氨基-6-氯苯甲酸酯。经X-射线衍射方法测定了其晶体结构,配合物属单斜晶系,空间群为P21/c,晶体学参数a=0.952 00(4)nm,b=0.918 55(3)nm,c=2.909 12(12)nm,β=93.187(2)°,V=2.539 97(17)nm3,Z=4,Dc=1.409 g.cm-3,μ(Mo Kα)=11.31 cm-1,F(000)=1 112,R1=0.038 2,wR2=0.098 6。中心锡与环己基碳原子和氧原子构成畸型四面体。对其结构进行量子化学从头计算,探讨了配合物的稳定性、分子轨道能量以及一些前沿分子轨道的组成特征。通过循环伏安法研究了其电化学性质。     

尿素晶体介电性能的量子化学计算

利用量子化学的第一性原理,在自洽场理论水平上对尿素晶体的线性和非线性光学介电性质进行了定量计算,获得了与实验值相符的理论计算结果.提供了一种解决分子晶体量子化学理论计算的新思路.     

Redox Potential and Crystal Chemistry of Hexanuclear Cluster Compounds

Most of TM₆-cluster compounds (TM = transition metal) are soluble in polar solvents, in which the cluster units commonly remain intact, preserving the same atomic arrangement as in solids. Consequently, the redox potential is often used to characterize structural and electronic features of respective solids. Although a high lability and variety of ligands allow for tuning of redox potential and of the related spectroscopic properties in wide ranges, the mechanism of this tuning is still unclear. Crystal chemistry approach was applied for the first time to clarify this mechanism. It was shown that there are two factors affecting redox potential of a given metal couple: Lever’s electrochemical parameters of the ligands and the effective ionic charge of TM, which in cluster compounds differs effectively from the formal value due to the bond strains around TM atoms. Calculations of the effective ionic charge of TMs were performed in the framework of bond valence model, which relates the valence of a bond to its length by simple Pauling relationship. It was also shown that due to the bond strains the charge depends mainly on the atomic size of the inner ligands.