TS-1分子筛酸性的固体核磁表征

钛硅分子筛是一种具有广泛用途的环境友好催化剂 .它的开发和应用 ,使分子筛由酸催化作用扩展到了催化氧化过程 .TS- 1作为氧化催化剂 ,在以双氧水为氧化剂的烯烃环氧化、芳烃环的羟基化、环己酮的肟化、醇以及饱和烃的氧化等反应中显示出优良的催化性能 ,因而倍受关注 [1～ 4 ] .然而 ,尽管钛以四配位的形式进入分子筛的骨架 ,但仍然存在弱酸中心 ,这种弱酸中心在一些催化氧化反应中起着一定的作用[5] .人们对分子筛的酸性进行了长期研究 ,从最初的化学滴定法到量热法以及 NH3- TPD,尽管可得到分子筛酸性位的一些信息 ,但无法区分酸的种…     

室温固相反应制备Keggin结构杂多酸铵盐纳米粒子

纳米材料由于其量子尺寸效应及表面效应而在磁、光、电等方面显示出许多常规粒子所不具有的特性[1] .纳米材料成功应用的实例及潜在应用前景推动了各种纳米粉末的合成及合成方法的发展 [2～ 4 ] .利用低温固相反应制备纳米粒子尚不多见 ,但已有报道 [5,6] .多金属氧酸盐因其独特的结构而具有较高的催化活性、导电性、磁性、光电致变色性以及抗病毒活性 ,因而有着广阔的应用前景 ,这些方面的研究已越来越引起人们的兴趣 [7～ 10 ] .本文采用室温固相反应首次制备了多金属氧酸盐纳米粒子 (NH4 ) 3PMo12 O4 0 · 9H2 O(1 )和 (NH4 ) 3PW12…     

Nucleophile‐Initiated Catalytic and Multicomponent Reactions

A number of well‐known reactions, proceed through the intermediacy of dipolar/zwitterionic species generated via the addition of a neutral nucleophile with an unsaturated electrophile. A mechanistic understanding of these reactions was made possible by seminal contributions of Huisgen. The design of novel reactions based on such dipolar species was, however, not pursued in detail for a long time. Our efforts to exploit various reactivity profiles available for the zwitterionic/dipolar intermediates have resulted in the discovery of a large number of novel, convenient protocols to access a wide variety of products. The nucleophilic initiators may participate in the reaction or play a mediating role depending upon the nature of nucleophile, its quantity and the reaction conditions. In a majority of these transformations two electrophilic components, that would normally be inert towards each other, are combined by the intermediacy of a nucelophile. A brief summary of such nucleophile‐initiated novel reactions that were developed in our research group are described. Reactions involving a variety of nucleophiles such as phosphines, pyridine, quinoline, isoquinoline, isocyanides, dimethoxycarbene and N‐heterocyclic carbenes (NHCs) are discussed.     

Mechanochemical Radical Boronation of Aryl Diazonium Salts Promoted by Sodium Chloride

Arylboronates are helpful building blocks in organic synthesis. Here, we present an efficient mechanochemical synthesis of arylboronates from arene diazonium salts. Importantly, this transformation was significantly enhanced by sodium chloride, which probably promotes the decomposition of diazonium salts via anion exchange. Chloride anions also participate in the formation of strongly reducing Cl−B anion radical intermediate that promotes radical chain reaction. The reaction proceeds more efficiently with a small amount of polar solvent as a liquid-assisted grinding additive. Quantum chemical calculations support the mechanistic proposal.     

The multicomponent reaction of dimethoxycarbene, dimethyl butynedioate and electrophilic styrenes: an unprecedented synthesis of highly substituted cyclopentenone acetals

The zwitterionic species generated by the addition of dimethoxycarbene to dimethyl butynedioate is trapped by arylidenemalononitrile to yield cyclopentenone derivatives.     

One-pot, four-component reaction of isocyanides, dimethyl acetylenedicarboxylate, and cyclobutene-1,2-diones: a synthesis of novel spiroheterocycles

Isocyanides, dimethyl acetylenedicarboxylate, and cyclobutene-1,2-diones react in one-pot to afford novel spirocyclic compounds with double insertion of the isocyanide.     

Zwitterionic Salts from the Reaction of Symmetrical and Unsymmetrical (thio)Barbituric Acids with 2‐Pyridinecarbaldehyde under Solvent‐free Condition

A simple and efficient synthesis for the preparation of unusual charge‐separated pyridinium (thio)barbiturate zwitterion derivatives was achieved via a one‐pot reaction of (thio)barbituric acid derivatives and 2‐pyridinecarbaldehyde under solvent‐free condition and also in methanol under refluxing. The structure of the compounds was confirmed by ¹H NMR, ¹³C NMR, FT‐IR, mass and X‐ray analysis. The mechanism of the formation is discussed. Instead, no related pyridinium zwitterion was afforded from the reaction between dimedone and 2‐pyridinecarbaldehyde under the same conditions and its xanthene derivative was obtained.     

绿色化学与铬盐工业的新一代产业革命

本文介绍了铬盐生产的绿色化学研究的内容和方法, 所开拓的熔盐液相氧化-高浓介质单向分离-介稳态相分离-碳化循环转化的多相反应与分离系统的绿色化学新原理, 资源深度利用-反应介质内循环-零排放的完整绿色工业化学体系。     

Lithium Ion Motion in Lithium Nitridoborate Chalcogenides Li5(BN2)Ch (Ch = Se,Te)

The compounds Li₅(BN₂)Se and Li₅(BN₂)Te were synthesized at 900 °C in a closed system utilizing weld shut niobium ampoules and obtained as white microcrystalline powders. Their crystal structures were solved and refined on the basis of single‐crystal X‐ray diffraction data with the space group I4₁md [a = 6.3983(4) Å, c = 11.1072(9) Å for Li₅(BN₂)Se and a = 6.5878(3) Å, c = 11.4382(7) Å for Li₅(BN₂)Te]. The temperature dependent Li⁺ motion was investigated by ⁷Li MAS NMR spectroscopy.     

Solid-state NMR study of biodegradable starch/polycaprolactone blends

Abundant literature exists on starch or modified starch blended with biodegradable polyesters to achieve good performance with cheap compost plastics. The level of miscibility in these blends is one of the most relevant parameters. In the present study, solid-state ¹H and ¹³C NMR spectra, as well as carbon spin-lattice relaxation times T₁(C) and proton spin-lattice relaxation times T₁(H) and proton spin-lattice relaxation times in the rotating frame T_1ρ(H) of biodegradable starch (or starch formate)/polycaprolactone (PCL) (or polyester (PE) oligomers) blends and samples of the neat components were measured. From the T_1ρ(H) and T₁(H) relaxation times it follows that blends starch/PCL, starch/PE-oligomers and starch formate/PE-oligomers are phase separated even on the scale of 20-110 nm. On the contrary starch formate/PCL blend is phase separated on the scale 2.5-12 nm but homogeneously mixed on the scale 20-90 nm. Moreover, shorter T₁(C) and especially T_1ρ(H) values found for the starch or starch formate component in all these blends in comparison with neat samples show that molecular mobility of starch and starch formate segments is affected by blending. This indicates some miscibility also in phase separated blends which can happen in amorphous channels of starch.     

The Coordination Chemistry of f-Block Elements in Molten Salts

The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties.     

The synthesis of functionalized pyranophenalenones

Abstract  Protonation of the highly reactive 1:1 intermediate produced in the reaction between alkyl or aryl isocyanides and electron-deficient acetylenic esters with 3-hydroxy-1H-phenalene-1-one leads to a vinylisonitrilium cation, which undergoes an addition reaction with the conjugate base of the 3-hydroxy-1H-phenalene-1-one to produce biologically interesting dialkyl 10-(alkyl or arylamino)-7-oxo-7H,8H-naphtho[1,8-gh]chromene-8,9-dicarboxylates in moderate to fairly good yields at room temperature. Graphical abstract        

Three-component reaction of imidazoles,cyanophenylacetylene, and chalcogens: stereoselective synthesis of 3-alkenyl-2-imidazolethiones and -selones

The three-component reaction of 1-substituted imidazoles, cyanophenylacetylene, and elemental sulfur or selenium proceeds readily (for sulfur at room temperature without solvent, and for selenium in boiling MeCN) to stereoselectively afford 3-(Z)-cyanophenylethenyl-2-imidazolethiones or -selones in yields ranging 39–97% (for thiones) and 39–84% (for selones). In this reaction, tellurium is inactive both under the above conditions and upon heating (50–55 °C) in DMSO, instead, only the C(2)-vinylation of the imidazole ring in up to 98% yield takes place. The Z-stereoselectivity of the reaction is close to 100% (for sulfur) and reaches 91–99% (for selenium). The reaction involves the zwitterionic adduct of imidazoles with cyanophenylacetylene, which converts to the carbene via proton transfer (from the imidazole 2 position to the carbanionic site of the zwitterion) further reacting with chalcogens.     

Reactivity in the System Copper/Arsenic/Sulfur II. The Formation of CuAsS, (Lautite)

The reaction pathways during the synthesis of CuAsS have been studied with the DTA in the range 25 — 810 °C with a heating rate of 10 K/min. Educts, intermediates, and products were characterized by X‐ray diffraction at room and elevated temperatures. Educts were the corresponding elements and the binary compounds As₄S₄, As₂S₃, Cu_3—xAs, Cu_5—δAs₂, Cu₂S, and CuS. The 13 examined educt mixtures can be divided into four groups specified by their thermal effects observed during the reaction. Mixtures of group I contain copper arsenides and arsenic sulfides, those of group II and III arsenic and copper sulfides, and arsenic sulfides and copper, respectively. Group IV includes mixtures showing individual reactions. In all cases the reaction to CuAsS proceeds stepwise. The reaction is not completed at 574 °C, the decomposition temperature of CuAsS, because the product is still associated with Cu_12+xAs_4+yS₁₃ , As, and to a lesser amount with Cu_1.81S. Nevertheless, a consecutive run in which the samples were heated above the liquidus temperature shows no exothermic reaction effect. When the mixtures were cooled at 10 K/min after the runs, no CuAsS was found in the X‐ray experiments. Only Cu_12+xAs_4+yS₁₃ and As were then observed.     

Solid-state,optical-rotation measurements on macromolecules using powder-suspensions

Summary We report techniques for measuring optical rotation of suspended solids, including dissymmetric molecular crystals (e.g. sodium chlorate and bromate), synthetic polymers, polypeptides and biopolymers. Examples include poly(triphenylmethyl methacrylate), poly-S-lactide, poly-L-hydroxyproline, hemocyanine, cellulose acetate andRNA. The results indicate that optical rotation measurements are sensitive to differences in secondary structure and can serve as a probe for structural differences between solid-state and solution.

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Messung der optischen Rotation von Makromolekülen im Festzustand unter Verwendung von Pulversuspensionen

Zusammenfassung Es wird über eine Methode zur Messung der optischen Rotation von Festkörpern in Suspensionen berichtet, wobei dissymetrische Kristalle (z. B. Natriumchlorat und -bromat), synthetische Polymere, Polypeptide und Biopolymere behandelt werden. Die Beispiele umfassen Poly(triphenylmethylmethacrylat), Poly-S-lactid, Poly-L-hydroxyprolin, Hemocyanin, Celluloseacetat undRNA. Die Ergebnisse zeigen, daß die optischen Rotationen bezüglich Unterschiede in der Sekundärstruktur empfindlich sind und daß diese Messungen als ein Maß für Strukturunterschiede zwischen Festzustand und Lösung herangezogen werden können.

     

Solid-state mechanochemical synthesis of ferrocene

Solid-state mechanochemical reactions of iron(II) chloride with cyclopentadienides of alkaline metals or thallium, which lead to the formation of ferrocene, were studied. The dependence of the yield of the product on the parameters of mechanical loading for the reaction with cyclopentadienylthallium was determined.     

Theoretical Investigation of the Solid State Reaction of Silicon Nitride and Silicon Dioxide forming Silicon Oxynitride (Si2N2O) under Pressure

The high‐pressure behavior of Si₂N₂O is studied for pressures up to 100 GPa using density functional theory calculations. The investigation of a manifold of hypothetical polymorphs leads us to propose two dense phases of Si₂N₂O, succeeding the orthorhombic ambient‐pressure polymorph at higher pressures:a defect spinel structure at moderate pressures and a corundum‐type structure at very high pressures. Taking into account the formation of silicon oxynitride from silicon dioxide and silicon nitride and its pressure dependence, we propose five pressure regions of interest for Si₂N₂O within the pseudo‐binary phase diagram SiO₂‐Si₃N₄: (i) stability of the orthorhombic ternary phase of Si₂N₂O up to 6 GPa, (ii) a phase assemblage of coesite, stishovite, and β‐Si₃N₄ between 6 and 11 GPa, (iii) a possible defect spinel modification of Si₂N₂O between 11 and 16 GPa, (iv) a phase assemblage of stishovite and γ‐Si₃N₄ above 40 GPa, and (v) a possible ternary Si₂N₂O phase with corundum‐type structure beyond 80 GPa. The existence of both ternary high‐pressure phases of Si₂N₂O, however, depends on the delicate influence of configurational entropy to the free energy of the solid state reaction.     

Luminescence Tuning of Sr8MgCe(PO4)7:Eu2+,Mn2+ Phosphors: Structure Refinement,Site Occupancy,and Energy Transfer

Sr₈MgCe(PO₄)₇:Eu²⁺,Mn²⁺ phosphor with whitlockite‐type structure was prepared by a combustion‐assisted solid‐state reaction. The crystal structure and luminescence properties were investigated. Under UV radiation, Sr₈MgCe(PO₄)₇ host exhibits a violet‐blue emission band from Ce³⁺ ions. When Eu²⁺/Mn²⁺ are doped into the host, the samples excited with 270 nm UV radiation present multicolor emissions due to the energy transfer (ET) from Ce³⁺ to Eu²⁺/Mn²⁺. The emitting color of Sr₈MgCe(PO₄)₇:Eu²⁺ can be tuned from violet‐blue to yellow‐green, whereas Sr₈MgCe(PO₄)₇:Mn²⁺ can emit red light. Under excitation with long wavelength at 360 nm, Sr₈MgCe(PO₄)₇:Eu²⁺ phosphor shows a broadband emission from 390 to 700 nm, which is attributed to the 4f⁶5d¹→4f⁷ transition of Eu²⁺ without the contribution from Ce³⁺ emission. Tunable full‐color emitting light can be achieved in the Eu²⁺ and Mn²⁺‐codoped Sr₈MgCe(PO₄)₇ phosphor by ET_Eu–Mn through control of the levels of doped Eu²⁺ and Mn²⁺ ions. These results suggest that Sr₈MgCe(PO₄)₇:Eu²⁺,Mn²⁺ phosphor has potential applications in NUV chip pumped white LEDs.