Liquid-Like Phase of N,N-Dimethylpyrrolidinium Iodide Impregnated into COFs Endows Fast Lithium Ion Conduction in the Solid State

A novel kind of solid-state lithium electrolyte was fabricated by impregnating organic ionic plastic crystals (OIPCs) into the pores of covalent organic frameworks (COFs). The liquid-like phase of confined N,N-dimethylpyrrolidinium iodide (P_1,1I) and the ordered nanochannels of COFs simultaneously stimulated the lithium ion conduction.     

The temperature dependence of the HO2 + HO2 reaction

The temperature dependence of the rate constant for the reaction HO₂ + HO₂ → H₂O₂ + O₂ (2k₁) has been determined using flash photolysis techniques, over the temperature range 298–510 K, in a nitrogen diluent at a total pressure of 700 Torr. The overall second order state constant is given by k₁ = (4.14 ± 1.15) × 10^?13 exp[(630 ± 115)/T] cm³ molecule^?1 s^?1, where the quoted errors refer to one standard deviation. This result is compared with previous findings and the negative activation energy is shown to be consistent with the observation that the rate constant is pressure dependent at 700 Torr.     

Effect of autoclaving on zinc oxide in the presence of sulphate ions

The effect of autoclaving a zinc oxide preparation containing SO^2?₄ under 5 and 10 atmospheres is studied by combining X-ray diffraction, differential thermal analysis, thermogravimetry and IR spectroscopy. Textural measurements are also carried out on the parent samples and those produced in the temperature range 200–1000°C.A new phase of a basic carbonates?ulphate, including ammonia in its coordination shell, is observed in the original preparation and having its d distances at 11.060, 8.954 and 2.714 Å. This is transformed to another phase at ～180°C which is also the main phase characterizing the autoclaved samples, and belongs to a basic zinc oxide—sulphate possessing d distances at 7.055, 2.468 and 2.805 Å. Autoclaving the oxide preparation under 10 atm gives hexagonal zinc oxide of high purity and crystallinity at 1000°C. An empirical formula is given for the oxide preparation which describes the different decomposition stages observed. At ～390°C, a reversible reduction process comprising oxygen evolution is observed.Autoclaving increases the area of the parent oxide and at temperatures below 600°C is a function of the structural changes. The autoclaving pressure is insignificant ?600°C.Pore structure analysis showed all the samples to be predominantly mesoporous, coexisting with some micropores except that autoclaved under 5 atm and heated at 250°C which is predominantly microporous. Autoclaving under 5 atm causes narrowing of the pores for products below 600°C. Autoclaving has little effect on the average pore radius ?600°C.Evaluation of the average pore radius from the constructed t-curves for parallel-plate pore idealization is discussed.     

Design of Thermochromic Luminescent Dyes Based on the Bis(ortho‐carborane)‐Substituted Benzobithiophene Structure

To obtain solid‐state emissive materials having stimuli‐responsive luminescent chromic properties without phase transition, benzobithiophenes modified with two o‐carborane units having various substituents in the adjacent phenyl ring in o‐carborane were designed and synthesized. Their emission colors were strongly affected not only by the substituents at the para‐position of the phenyl ring but also by molecular distribution in the solid state. In particular, the emission colors were changed by heating without crystal phase transition. It was proposed that their thermochromic properties were correlated not with isomerization but with the molecular motion at the distorted benzobithiophene moiety.     

Silica‐Grafted Tris(neopentyl)aluminum: A Monomeric Aluminum Solid Co‐catalyst for Efficient Nickel‐Catalyzed Ethene Dimerization

A silica‐supported monomeric alkylaluminum co‐catalyst was prepared via surface organometallic chemistry by contacting tris(neopentyl)aluminum and partially dehydroxylated silica. This system, fully characterized by solid‐state ²⁷Al NMR spectroscopy augmented by computational studies, efficiently activates (ⁿBu₃P)₂NiCl₂ towards dimerization of ethene, demonstrating comparable activity to previously reported dimeric diethylaluminum chloride supported on silica. Three types of aluminum surface species have been identified: monografted tetracoordinated Al species as well as two types of bisgrafted Al species—tetra‐ and pentacoordinated. Of them, only the monografted Al species is proposed to be able to activate the (ⁿBu₃P)₂NiCl₂ complex and generate the active cationic species.     

Knight Shift in 13C NMR Resonances Confirms the Coordination of N-Heterocyclic Carbene Ligands to Water-Soluble Palladium Nanoparticles

The coordination of N-heterocyclic carbene (NHC) ligands to the surface of 3.7 nm palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the ¹³C resonance of the carbenic carbon. In order to validate this coordination, PdNPs with sizes ranging from 1.3 to 4.8 nm were prepared by thermal decomposition or reduction with CO of a dimethyl NHC Pd^II complex. NMR studies after ¹³CO adsorption established that the KS shifts the ¹³C resonances of the chemisorbed molecules several hundreds of ppm to high frequencies only when the particle exceeds a critical size of around 2 nm. Finally, the resonance of a carbenic carbon is reported to be Knight-shifted to 600 ppm for ¹³C-labelled NHCs bound to PdNPs of 3.7 nm. The observation of these very broad KS resonances was facilitated by using Car–Purcell–Meiboom–Gill (CPMG) echo train acquisition NMR experiments.     

Na2BaMQ4 (M=Ge,Sn; Q=S,Se): Infrared Nonlinear Optical Materials with Excellent Performances and that Undergo Structural Transformations

Infrared nonlinear optical (IR NLO) materials with excellent performances are particularly important in laser technology. However, to design and synthesize an efficient IR NLO material with a balance between the optical band gap and the NLO coefficient is still a huge challenge. With this in mind, four new IR NLO materials Na₂BaSnS₄, Na₂BaSnSe₄, Na₂BaGeS₄, and Na₂BaGeSe₄ were successfully designed and synthesized. The compounds exhibit excellent properties with a suitable balance of band gap and NLO coefficient measured for Na₂BaSnS₄ (3.27 eV and about 17×KDP, that is, about 17 times that of KH₂PO₄ (KDP)) and Na₂BaGeS₄ (3.7 eV and about 10×KDP), demonstrating that the systems satisfy the key requirements as promising IR NLO candidates. Remarkably, the new compounds also undergo a novel structural transformation from tetragonal to trigonal systems, the first time that this has been reported for quaternary metal chalcogenides.     

Stereoselective Solid‐State Synthesis of Substituted Cyclobutanes Assisted by Pseudorotaxane‐like MOFs

Regioselective photodimerization of trans‐4‐styrylpyridine (4‐spy) derivatives is performed using pseudorotaxane‐like Zn‐based metal organic frameworks MOFs as templates. The formation of rctt‐HT (head‐to‐tail) dimers is achieved by confining pairs of coordinated 4‐spy derivative ligands within hexagonal windows and then irradiating them with UV light. It is also possible to achieve a photodimerization reaction where two different substituted 4‐spy ligands are included in such a MOF material. The ether bond formation is employed to protect the sensitive ‐OH group of HO‐spy and the methyl group of CH₃O‐spy is subsequently removed after the formation of cyclobutane derivative in the CH₃O‐spy‐based MOF. Introducing substituents at the 2‐ or 3‐position of the phenyl group of 4‐spy does not significantly affect the rate of the dimerization process except in the case of the strongly electron‐withdrawing nitro group where the rate is significantly decreased. These results are in striking contrast to the mixtures of photoproducts and low yields obtained by untemplated photodimerization in organic solvents.     

Li(Na,K)Ba(Sr,Ca)B9O15∶Eu3+荧光粉的制备及发光性能

采用高温固相法在空气气氛下合成了一系列Eu³⁺掺杂硼酸盐基质荧光粉。用X射线衍射、荧光光谱以及色坐标等手段对荧光粉的晶相和发光性能进行表征。通过LiBaB₉O₁₅中的碱金属以及碱土金属之间的相互取代,研究了基质组成的改变对荧光粉发光性能的影响。结果表明,在Li(Na,K)Ba(Sr,Ca)B₉O₁₅∶0.07Eu³⁺系列荧光粉中,LiSrB₉O₁₅∶0.07Eu³⁺荧光粉的发光强度最强。考察了煅烧温度、保温时间和Eu³⁺掺杂量对LiSrB₉O₁₅∶Eu³⁺荧光粉晶相和发光性能的影响,煅烧温度为750 ℃,保温时间为1~5 h时,样品的结晶性均良好。Eu³⁺掺杂量为0.52时,LiSrB₉O₁₅∶Eu³⁺荧光粉的发光强度最强。当x≥0.42(x=0.42,0.47,0.52,0.57)时,LiSrB₉O₁₅∶xEu³⁺色坐标均接近标准红光(0.67,0.33)。比较了LiSrB₉O₁₅∶xEu³⁺(x=0.02~0.57)荧光粉的611 nm(⁵D₀→⁷F₂)和586 nm(⁵D₀→⁷F₁)处发射峰相对强度比值R,R值变化不大,说明多数Eu³⁺在晶格中处于非反演对称中心的格位;比较了LiSrB₉O₁₅∶0.52Eu³⁺荧光粉和商用Y₂O₃∶Eu³⁺荧光粉的发光特性,在260 nm波长激发下,LiSrB₉O₁₅∶0.52Eu³⁺荧光粉的发光强度弱于Y₂O₃∶Eu³⁺荧光粉;在362 nm和394 nm波长激发下,LiSrB₉O₁₅∶0.52Eu³⁺荧光粉的发光强度强于Y₂O₃∶Eu³⁺荧光粉。