Synthesis of tetrasubstituted thiophenes from pyridinium 1,4-zwitterionic thiolates and modified activated alkynes

Pyridinium 1,4-zwitterionic thiolates were applied to a formal [3 + 2] annulation reaction with modified activated alkynes, affording various tetrasubstituted thiophenes with aryl, alkenyl, alkyl or silyl group at the special position. The structural modification of alkyne substrates enabled the synthesis of diverse thiophenes to be achieved using the pyridinium 1,4-zwitterionic thiolates as the sulfur-containing building blocks. This approach is metal-free and catalyst-free.     

中高能电子被甲烷及氯代甲烷散射的总截面

利用可加性规则，使用HartreeFock波函数，采用由束缚原子概念修正过的复光学势（由静 电势、交换势、修正极化势及吸收势这四部分组成），在较大的能量(30—5000eV)范围内对 电子被甲烷及氯代甲烷（CH₄，CCl₄，CHCl₃，CH₂Cl₂和CH ₃Cl）散射的总截面进行了计算，且将计算结果与实验结果及其他理论计算 结果进行 了比较.结果表明，利用被束缚原子概念修正过的复光学势及可加性规则进行计算，所得结 果的精度要比利用未被束缚原子概念修正的复光学势及可加性规则进行计算得到的结果好很 多.因此，在复光学势中采用束缚原子概念可提高电子被分子散射的总截面的计算准确度. 关键词： 电子散射 可加性规则 束缚原子 总截面     

Molecular insight into structures of monocationic and dicationic ionic liquids in mica slits

Structures of ionic liquids (ILs) 1-decyl-3-methylimidazolium bis(trifluoromethanesulfonyl)azanide ([C₁₀mim][TFSA]) and 1-decyl-dimethylimidazolium bis(trifluoromethanesulfonyl)azanide ([C₁₀(mim)₂](TFSA)₂) in different-sized mica slits have been investigated using molecular dynamics simulations. Ion density and angular distributions for monocationic IL [C₁₀mim][TFSA] were analysed to elucidate the IL structures under different surface charges and especially their changes in the direction perpendicular to the surfaces. [C₁₀mim][TFSA] formes in bilayers, compatible with existing models of ILs with long alkyl chains. For dicationic IL [C₁₀(mim)₂](TFSA)₂, cations adjacent to the mica surface tend to stay parallel to the surface with both positively charged rings absorbed. While near the centre of the slit, dications show the weak tendency of orientation distribution, more random than [C₁₀mim]⁺ ions. Structures of [C₁₀(mim)₂](TFSA)₂ cannot be described by bilayer models. Additionally, the in-plane arrangement of [C₁₀mim][TFSA] is more ordered when K⁺ ions completely neutralise the negative charge of the mica surface, and [C₁₀mim]⁺ ions tend to be located in hexagonal mica lattices with two aluminium atoms in replacement of silicon atoms. [TFSA]^? ions are constrained by the neighbouring K⁺ ions absorbed onto mica lattices.     

Perfect matchings extend to two or more hamiltonian cycles in hypercubes

Kreweras conjectured that every perfect matching of a hypercube $Q_n$ for $n\ge 2$ can be extended to a hamiltonian cycle of $Q_n$. Fink confirmed the conjecture to be true. It is more general to ask whether every perfect matching of $Q_n$ for $n\ge 2$ can be extended to two or more hamiltonian cycles of $Q_n$. In this paper, we prove that every perfect matching of $Q_n$ for $n\ge 4$ can be extended to at least $2^{2^{n?4}}$ different hamiltonian cycles of $Q_n$.     

Lithium–Lanthanide Bimetallic Metal–Organic Frameworks towards Negative Electrode Materials for Lithium-Ion Batteries

Novel lithium–lanthanide (Ln: cerium and praseodymium) bimetallic coordination polymers with formulas C₁₀H₂LnLiO₈ (Ln: Ce (CeLipma) and Pr (PrLipma)) and C₁₀H₃CeO₈ (Cepma) were prepared through a simple hydrothermal method. The three compounds were characterized by means of FTIR spectroscopy, X-ray diffraction, single-crystal X-ray diffraction, SEM, TEM, and X-ray photoelectron spectroscopy. The results of structural refinement show that they belong to triclinic symmetry and P space group with cerium (or praseodymium) and lithium cations, forming coordination bonds to oxygen atoms from different pyromellitic acid molecules, and leading to the construction of 3D structures. It is interesting to note that the frameworks exclude any coordination water and lattice water. As an electrode material for lithium-ion batteries, CeLipma exhibits a maximum capacity of 800.5 mAh g⁻¹ and a retention of 91.4 % after 50 cycles at a current density of 100 mA g⁻¹. The favorable electrochemical properties of the lanthanide coordination polymers show potential application prospects in the field of electrode materials.     

Decomposable super‐simple NRBIBDs with block size 4 and index 6

Necessary conditions for the existence of a super‐simple, decomposable, near‐resolvable ‐balanced incomplete block design (BIBD) whose 2‐component subdesigns are both near‐resolvable ‐BIBDs are (mod ) and . In this paper, we show that these necessary conditions are sufficient. Using these designs, we also establish that the necessary conditions for the existence of a super‐simple near‐resolvable ‐RBIBD, namely (mod ) and , are sufficient. A few new pairwise balanced designs are also given.     

Comparative XPS study between experimentally and naturally weathered pyrites

A comparative study has been carried out between experimentally and naturally weathered pyrites. Both were found to share similar species of weathering products and a similar weathering mechanism. The weathering products could be divided into sulphur-bearing or iron-bearing groups. The sulphur-bearing group was comprised of sulphate, sulphite, thiosulphate, elemental sulphur, polysulphide, and mono-sulphide. The iron-bearing group was comprised of goethite, hematite or magnetite, and iron sulphate. The weathering structural profile was also similar for both types of weathering, being composed of a surficial layer and a transitional layer. The surficial layer was made up of both the sulphur-bearing and the iron-bearing products, while the transitional layer was comprised of goethite, and hematite or magnetite. The inward migration of the weathering interface was stimulated by the diffusion of oxygen and moisture. The oxygen was considered to preferably squeeze the iron to form goethite, and the ferric ions of goethite to have acted as a bridge for electron transfer between the oxygen and bulk S₂²⁻ and Fe²⁺ of pyrite.