A structurally perfect S = (1/2) kagomé antiferromagnet

The syntheses and magnetic susceptibilities of a pure series of rare copper minerals from the atacamite family with general formula ZnxCu4-x(OH)6Cl2 (0 相似文献   

Ethenedithione (S=C=C=S): Does It Obey Hund's Rule?

Significantly higher in energy (24 kJ mol⁻¹) than the triplet ground state (³Σ_g⁻) is the ¹Δ_g state of ethenedithione (S=C=C=S), in agreement with Hund's rule. This result was obtained from high-level ab initio calculations. Thus, ethenedithione cannot, as had been proposed, be considered as the first example for the violation of Hund's rule in an equilibrium structure.     

On the Double Salt Formation in the Systems Rb2SeO4=ZnSeO4=H2O andCs2SeO4=ZnSeO4=H2O at 25°C

 The solubilities in the systems Rb₂SeO₄=ZnSeO₄=H₂O and Cs₂SeO₄=ZnSeO₄=H₂O at 25°C were studied by the method of isothermal decrease of supersaturation. Comparatively wide crystallization fields of the double salts Rb₂Zn(SeO₄)₂ċ6H₂O and Cs₂Zn(SeO₄)₂ċ6H₂O are observed in the solubility diagrams. The double salts form monoclinic crystals which are isostructural with those of the corresponding rubidium and cesium zinc sulfate hexahydrates. TG and TDA measurements indicate that the double salts lose their crystallization water in one step in the temperature intervals of 50–160°C (rubidium salt) and 70–150°C (cesium salt).     

Synthesis, structure, and properties of M[VO2(XO4)(H2O)2] · H2O (X = S, M = K, Rb, NH4, Tl; X = Se, M = K, Rb, NH4)

Keeping of MVO(XO₄)₂ under saturated vapor pressure at room temperature resulted in the synthesis of a number of isostructural complexes M[VO₂(XO₄)(H₂O)₂] · H₂O, where X = S, M = K, Rb, NH₄, Tl and X = Se, M = K, Rb, NH₄. The conclusion about the isostructural nature of the synthesized sulfate and selenate compounds was based on X-ray diffraction and vibrational spectroscopy data. Characteristic features of the thermal decomposition of M[VO₂(XO₄)(H₂O)₂] · H₂O on heating in air were identified. It was shown that K[VO₂(SeO₄)(H₂O)₂] · H₂O tends to undergo spontaneous dehydration under ambient conditions to give the monohydrate K[VO₂(SeO₄)(H₂O)].     

The heterometallic two-dimensional structure in the Ba2[Cu(L)](ClO4)2 · nH2O crystals (L = ethylenediaminetetraacetate, n = 6; L = ethylenediaminetetra-3-propionate, n = 5)

The crystals of Ba₂[Cu(Edtp)](ClO₄)₂ · 5H₂O (i) contain the tetragonal-pyramidal complexes of Cu(II) with ethylenediaminetetra-3-propionate ion with one noncoordinated propionate group. The [Cu(Edtp)]²⁻ complex ions and two sorts of the Ba atoms form two-dimensional supramolecular aggregate. Two Ba(1) atoms and one Cu atom form a tetramer by means of the coordinated carboxyl group and a free propionate group. The tetramers are united through the propionate group into ribbons, which are joined by the Ba(2) atoms into the layers. The coordination sphere of each B atom involves four water molecules, including two bridging water molecules. The perchlorate ions are also coordinated by the Ba atoms, one Ba atom acting as a bridge. The structure of the previously studied Ba₂[Cu(Edta)](ClO₄)₂ · 6H₂O (II) crystals with the hexadentate ethylenediaminetetraacetate ion is shown to be similar to that of complex I, but in the case of II, the Ba atoms are equivalent as regards the number of the complex anions bound to them. Original Russian Text ? M. Zabel, V.I. Pavlovskii, A.L. Poznyak, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 1, pp. 55–60.     

连续二氧化碳激光敏化氧化CF2HCL,CF2=CF2,CF2=CFCl,CHCl3,CHCl=CCl2和CH2=CH2

本文报道了连续二氧化碳激光敏化氧化CF_2HCl,CF_2==CF_2,CF_2==CFCL,CHCl_3,CHCl==CCl_2和CH_2==CH_2的反应,讨论了某些反应的机制。结果表明,激光敏化方法可以使不能直接吸收激光的反应物分子在气相中发生反应,并有可能产生卡宾。     

微波辅助快速制备2D/1D ZnIn2S4/TiO2 S型异质结及其光催化制氢性能

The threat and global concern of energy crises have significantly increased over the last two decades. Because solar light and water are abundant on earth, photocatalytic hydrogen evolution through water splitting has been considered as a promising route to produce green energy. Therefore, semiconductor photocatalysts play a key role in transforming sunlight and water to hydrogen energy. To date, various photocatalysts have been studied. Among them, TiO₂ has been extensively investigated because of its non-toxicity, high chemical stability, controllable morphology, and high photocatalytic activity. In particular, 1D TiO₂ nanofibers (NFs) have attracted increasing attention as effective photocatalysts because of their unique 1D electron transfer pathway, high adsorption capacity, and high photoinduced electron–hole pair transfer capability. However, TiO₂ NFs are considered as an inefficient photocatalyst for the hydrogen evolution reaction (HER) because of their disadvantages such as a large band gap (~3.2 eV) and fast recombination of photoinduced electron–hole pairs. Therefore, the development of a high-performance TiO₂ NF photocatalyst is required for efficient solar light conversion. In recent years, several strategies have been explored to improve the photocatalytic activity of TiO₂ NFs, including coupling with narrow-bandgap semiconductors (such as ZnIn₂S₄). Recently, microwave (MW)-assisted synthesis has been considered as an important strategy for the preparation of photocatalyst semiconductors because of its low cost, environment-friendliness, simplicity, and high reaction rate. Herein, to overcome the above-mentioned limiting properties of TiO₂ NFs, we report a 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction synthesized through a microwave (MW)-assisted process. Herein, the 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction was constructed rapidly by using in situ 2D ZnIn₂S₄nanosheets decorated on 1D TiO₂ NFs. The loading of ZnIn₂S₄ nanoplates on the TiO₂ NFs could be easily controlled by adjusting the molar ratios of ZnIn₂S₄ precursors to TiO₂ NFs. The photocatalytic activity of the as-prepared samples for water splitting under simulated solar light irradiation was assessed. The experimental results showed that the photocatalytic performance of the ZnIn₂S₄/TiO₂ composites was significantly improved, and the obtained ZnIn₂S₄/TiO₂ composites showed increased optical absorption. Under optimal conditions, the highest HER rate of the ZT-0.5 (molar ratio of ZnIn₂S₄/TiO₂= 0.5) sample was 8774 μmol·g^-1·h^-1, which is considerably higher than those of pure TiO₂ NFs (3312 μmol·g^-1·h^-1) and ZnIn₂S₄nanoplates (3114 μmol·g^-1·h^-1) by factors of 2.7 and 2.8, respectively. Based on the experimental data and Mott-Schottky analysis, a possible mechanism for the formation of the S-scheme heterojunction between ZnIn₂S₄ and TiO₂ was proposed to interpret the enhanced HER activity of the ZnIn₂S₄/TiO₂heterojunctionphotocatalysts.      

3,4-二-O-乙酰基-L-阿拉伯烯糖与HR—CH2—CH=CH2（R=O,CH2,NH,S）的Ferrier重排反应机理

采用密度泛函理论方法对3,4-二-O-乙酰基-L-阿拉伯烯糖与HR—CH2—CH=CH2(R=O,CH2,NH,S)反应的Ferrier重排反应机理进行了研究,并通过自洽场极化连续模型(PCM)模拟了苯和二氯化碳溶剂对反应历程的影响,计算了相应结构的单点能,考虑了2条可能的反应途径,获得了较优反应途径和反应速率控制步骤.研究表明:苯和二氯化碳溶剂的溶剂效应未对反应历程产生明显影响.R基电负性越大、体积越大以及H+的存在,均有利于该重排反应进行.     

Cl2+2HBr=2HCl+Br2反应的机理和应用

用密度泛函理论(DFT)B3LYP方法,取6-311G**基组,细致研究了反应Cl2+2HBr= 2HCl+Br2的机理,求得一系列四中心和三中心过渡态.双分子基元反应Cl₂+HBr®HCl+ BrCl和BrCl+HBr®Br₂+HCl的活化能(138.96和147.24 kJ· mol-1)小于Cl₂,HBr和BrCl的解离能,从理论上证明了标题反应将优先以分子与分子作用形式完成.将其应用于从HBr中回收溴,以Cl₂直接与HBr气体反应,生成的含溴混合气体,经冷凝并以四氯化碳吸收分离得到液溴和盐酸;溴的回收率大于96%,其含氯量小于3.0%.提供了运用基础理论解决生产中难题的成功例证.     

13C NMR on the S=1/2 antiferromagnetically coupled spin chain compound [PM·Cu(NO3)2·(H2O)2]n (PM=pyrimidine)

We present ¹³C NMR experiments on the S=1/2 antiferromagnetically coupled spin chain compound [PM·Cu(NO₃)₂·(H₂O)₂]_n (PM=pyrimidine) at temperatures 5–120 K. In the NMR spectra, we observe three pairs of double lines. From the angular dependence of the NMR shift, we assign the three line pairs to the three inequivalent C sites on the pyrimidine molecule C₄N₂H₄, with the splitting of the signal from each site into two lines caused by the hydrogen atom bound to C. We obtain the temperature dependence of the NMR shift, which exhibits a qualitatively different behavior for the three inequivalent C sites.     

固体强酸催化剂S2O2-8/ZrO2-Al2O3-M2O3(M=Cr,Ce,La)的制备

酯化反应;固体强酸催化剂S2O2-8/ZrO2-Al2O3-M2O3(M=Cr;Ce;La)的制备     

Ir2S3/ZnIn2S4催化下可见光诱导发生的烯烃/炔烃的高效硫氢化反应:Ir2S3的作用

C–S键的构建在化学中具有非常重要的意义.利用硫醇和烯烃/炔烃的硫氢化反应来构建C?S键是一种绿色、可持续和低成本的方法.本文以ZnCl2,InCl3,硫代乙酰胺为前驱体,在微量IrCl3存在条件下,通过一步溶剂热法制备得到了含有不同Ir摩尔比(0.5 mol％,1 mol％和2 mol％)的Ir2S3/ZnIn2S4...     

Static field induced magnetic relaxations in dinuclear lanthanide compounds of [phen2Ln2（HCOO）4（HCOO）2-2x（NO3）2x]（1,Ln=Gd and x=0.52; 2, Ln=Er and x=0.90; phen=1,10-phenanthroline）

Two dinuclear lanthanide (Ln) complexes, formulated as [phen2Ln2(HCOO)4(HCOO)2-2x(NO3)2x](1, Ln=Gd and x=0.52; 2, Ln = Er and x = 0.90; phen = 1,10-phenanthroline), were synthesized and characterized. They are isostructural. The dinuclear molecule consists of two Ln 3+ bridged by four formate groups and chelated by phen and formate/nitrate ligands, and the Ln 3+ possesses a coordination environment of distorted tri-capped trigonal prism of LnO 7 N 2 . Both compounds behave as paramagnets between 2 and 300 K, but display two static field induced magnetic relaxation processes. One is slow and of spin-lattice type, and it results from the lifting of Kramer’s degeneracy of the ground-states of both Gd 3+ and Er 3+ , and the other is fast, and it might be spin-spin type.     

磷改性失活TS-1高效催化C5=裂解制备C2=/C3=反应的研究

发展C₅⁼催化裂解高效制乙烯和丙烯(C₂⁼/C₃⁼)技术具有重要的研究意义及工业应用价值,其核心在于高效催化剂的开发.本文发展了以失活钛硅分子筛TS-1(De-TS-1)为催化剂的C₅⁼催化裂解过程,研究发现,P改性后的De-TS-1显示出优异的催化反应性能,C₂⁼+C₃⁼选择性与单程寿命分别达77.1%和213 h,其综合催化性能优于经典的ZSM-5催化剂.进一步研究表明,De-TS-1的Br?nsted性质符合C₅⁼裂解高效裂解的基本要求,P改性可进一步降低De-TS-1中Br?nsted酸的酸密度和酸强度,从而促进了目标产物C₂⁼/C₃⁼生成的主反应,抑制了C₅     

S2O2-8/ZrO2固体超强酸的研究

以Ｓ２Ｏ８＾２－浸渍无定形Ｚr（ＯＨ）４,制得较ＳＯ４＾２－／ＺrＯ２酸性更强的固体超强酸。用正丁烷异构化反应考察了Ｓ２Ｏ８＾２－／ＺrＯ２的酸性。结果表明,在对 ＺrＯ２有促进作用的非卤素阴离子中,Ｓ２Ｏ８＾２－是最好的促进剂。最佳焙烧条件下Ｓ２Ｏ８＾２－／ＺrＯ２固体超强酸比ＳＯ４＾２－／ＺrＯ２的酸性更强。３５℃下,Ｓ２Ｏ８＾２－／ＺrＯ２上正丁烷异构化反应速率较ＳＯ４＾２－／ＺrＯ２提高了１．２倍     

非金属氧化-还原对MO2/MO2-(M=N,S,Cl)的电子转移反应动力学

以Marcus-Hush电子转移理论为基础,提出了用量子化学密度泛函方法研究自交换和异交换电子转移反应的理论方案.在DFTB3LYP/6-311+G(2D)水平上研究了溶液中NO₂/NO₂^-,SO₂/SO₂^-和ClO₂/ClO₂^-等3个氧化-还原对的自交换以及它们之间的6个交叉电子转移反应的动力学性质,获得了与实验较为一致的结果.     

(1S,2S)-DPEN修饰的3%Ir/SiO2/2TPP催化苄叉丙酮的不对称加氢

在温和的条件下制备了负载型3%(w)Ir/SiO2/2TPP(三苯基膦)催化剂, 并且考察了(1S,2S)-1,2-二苯基乙二胺[(1S,2S)-DPEN]作为手性修饰剂对其催化苄叉丙酮不对称加氢反应性能的影响. 结果表明, 手性修饰剂(1S,2S)-DPEN的加入, 对苄叉丙酮不对称加氢反应活性和C=O加氢的选择性都有很好的促进作用. 经优化条件, 在40 ℃下, LiOH浓度为0.375 mol·L-1的甲醇溶液中, 氢气压力为6 MPa, 反应8 h后, 苄叉丙酮的转化率大于99.0%, 对不饱和醇的选择性大于99.0%, 不饱和醇的对映选择性(ee)值达到48.1%.