Chemical diffusion of oxygen in tin dioxide: Effects of dopants and oxygen partial pressure

Tin dioxide SnO_2−δ is a pronounced n-type electron conductor due to its oxygen deficiency. This study investigates the rate of chemical diffusion of oxygen in SnO_2−δ single crystals, which is a crucial step in the overall stoichiometry change of the material. The chemical diffusion coefficient D^δ was determined from conductivity- and EPR-relaxation methods. The temperature dependence was found to be . The dependence on crystal orientation, dopant content and oxygen partial pressure was below experimental error. The latter observation leads to the conclusion that the chemical diffusion coefficient is close to the diffusion coefficient of oxygen vacancies. Along with the relaxation process resulting from the chemical diffusion of oxygen, additional processes were observed. One of these was attributed to complications in the defect chemistry of the material. The relevance of the results for the kinetics of drift processes of Taguchi sensors is discussed.     

Synthesis and molecular structure of [Re2(μ:η-C24H18N4)(CO)6] containing the rtct-tetrakis(2-pyridyl)cyclobutandiyl ligand, derived from the reaction of [Re2(CO)8(MeCN)2] and 1,2-bis(2-pyridyl)ethene

The reaction of the labile compound [Re₂(CO)₈(CH₃CN)₂] with trans-1,2-bis(2-pyridyl)ethene (C₁₂H₁₀N₂) at room temperature in tetrahydrofuran affords the compounds [Re₂(μ:η³-C₁₂H₁₀N₂)(CO)₈] (1) and the oxidative addition product [Re₂(μ-H)(μ:η³-C₁₂H₉N₂)(CO)₇] (2). When the reaction is carried out at temperatures of refluxing tetrahydrofuran, besides compounds 1 and 2, the oxidative addition product [Re₂(μ-H)(μ:η⁴-C₁₂H₉N₂)(CO)₆] (3), the insertion product [Re₂(μ:η⁴-C₁₂H₁₀N₂)(CO)₈] (4) and [Re₂(μ:η⁶-C₂₄H₁₈N₄)(CO)₆] (5) are obtained. Compound 5 contains the organic ligand rtct-tetrakis(2-pyridyl)cyclobutandiyl which is derived from a [2 + 2] cycloaddition of 1,2-bis(2-pyridyl)ethene mediated by its coordination to the bimetallic framework. The molecular structures of 1, 2, 4 and 5 were confirmed by X-ray crystallographic studies.     

Pyrazine-2,3-dicarbonitriles substituted with maleimide derivatives

Syntheses and spectroscopic characteristics are reported for eight pyrazine-2,3-dicarbonitriles substituted with maleimide residue in addition to phenyl, 2-thienyl, or 2-furyl substituent. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1409–1414, September, 2007.     

铈改性NaZSM-5分子筛担载Pd催化剂上CO氧化性能研究

以浸渍法制备了一系列添加CeO2的Pd-Ce/NaZSM-5负载型催化剂．以C0氧化为 模型反应，考察了反应温度、Ce含量、预还原、空速及水蒸气等对C0氧化性能的影 响，并利用XIlD和朋等手段对催化剂体相及表面结构进行了表征．结果表明：加入 CeO2作助剂可明显提高催化剂的活性，且催化转化率随着反应温度及Ce含量的增加 而增加；随着空速的增加而降低；催化剂对水蒸气不敏感，在水蒸气存在的条件下 反应可连续进行720h以上保持C0完全转化；H2预还原作用使催化剂活性有所提高． XRD测试结果表明，催化剂中Pd组分处于高分散状态，Ceob的引入促进了N物种在 NaZSM—5载体上的分散．表面XPS分析证实催化剂表面Pd物种处于较高的氧化状态 ，且CeO2与Pd物种间存在协同作用．Pd的高分散及其与CeO2的相互作用是催化剂具 有高活性的关键．     

C–H· π Interaction and N·H–O Hydrogen Bonding in the Chair-like p-tert-Butylcalix[8]arene Complex Including Four Pyridine Molecules

Crystal structure analysis shows that the p-tert-butylcalix[8]arene host and its four pyridine guests sit around an inversion center in the P2₁/c crystal lattice. The monoclinic cell parameters and its volume are: a = 19.617(4), b = 9.912(2), c = 25.178(5) , = 101.03(3)°, V =4805.27(17) ³. For Z = 2 and Mw = 1614.18, the calculated density Dcalc = 1.116 g/cm³. A host calixarene molecule includes four pyridine guests in two different ways: by hydrogen bonding and by possible C–H· interaction between the molecules. The hydrogen bonding drives the host macrocycle into a chair-like conformation.     

Synthese und Geruch von Tricyclo[6.2.2.02, 7]dodecan-Derivaten

Summary The acetale-ketone9 was synthesized as precursor for the preparation of -santalol derivatives posessing a bicyclo[2.2.2]octane nucleus. After methylenation of the keto-group the subsequent acidic hydrolysis of the acetal leads via a Prins reaction of the liberated aldehyde with the methylene group to tricyclo[6.2.2.0^{2, 7}]dodecane derivatives. Their olfactory properties are described.

     

Theoretical Study on the Structures and Stability of Isomers and Complex of[Si,C,O,O] Sytem

A detailed singlet potential energy surface(PES) of [Si,C,O,O] system including a van der Waals (vdW) comples SiO……CO2,eight isomers,and twelve transiton states is investigated by MP2 and QCISD(T) (single-point)methods.At the final QCISD(T)/6-311 G(2df)//MP2/6-311G(d) level with zero-point energy included,the complex SiO……CO is found to be thermodynamically and kinetically the most stable species.Although eight ismoers are located as local energy minima,they are rather unstable toward isomerization to the dissociation fragments or comples.For the reaction of silocon atoms with carbon dioxide,two competitive reaction channels are found,and the primary pathway,which leads to the products of SiO and CO fragments,is the direct oxygen-abstraction process from carbon dioxide by silicon atom with a41.16 kJ/mol reaction barrier height.Our predications are in good agreement with previous experimental and theoretical studies.     

四甲氧基取代的二苯并并四苯(DBN)的合成, 晶体结构及聚集效应

本文从商品化的间溴苯甲醚和对甲氧基苯甲醛出发，通过傅-克酰基化反应、串联的羟醛缩合及1,4-迈克尔加成反应，得到三芳基取代的1,5-二酮，然后用查尔酮（Chalcone）作氧化剂，二酮与BF₃.Et₂O 反应形成吡喃鎓盐，再与苯基乙酸钠盐缩合得到芳香二溴代衍生物，产物的DMA溶液在DBU和钯催化剂的作用下，160°C 加热12 h进行脱卤化氢环化反应, 生成四甲氧基取代的二苯并并四苯（DBN）类衍生物。并报道了产物的晶体结构和在溶液中的聚集效应。     

A liquid chromatography-mass spectrometry method for the quantification of both etoricoxib and valdecoxib in human plasma

A practicable and selective liquid chromatography-mass spectrometry assay for the determination of two cyclooxygenase-2 inhibitors, etoricoxib and valdecoxib, in human plasma is presented. The analytical technique is based on reversed-phase high-performance liquid chromatography (HPLC) coupled to atmospheric pressure chemical ionisation (APCI) mass spectrometry (Finnigan Mat LCQ ion trap). Mass analysis was performed in the positive ion mode. The ion trap was operated in the tandem MS mode (MS2) and the transitions of etoricoxib (m/z 359.2 --> 280.3) and valdecoxib (m/z 315.1 --> 235.1) were followed by selected reaction monitoring. Retention times of etoricoxib and valdecoxib were 1.05 and 1.08 min, respectively. The method was validated over a linear range 10-2500 and 5-1000 microg/L using the other substrate as internal standard. After validation, the method was used to study the pharmacokinetic pro fi le of etoricoxib or valdecoxib in a healthy volunteer after administration of a single oral dose (valdecoxib, 20 mg; etoricoxib, 90 mg). The presented method was suf fi cient to cover more than 90% of the area under the plasma concentration time curve.     

2-取代亚肼基-1,3-二硫杂环戊烷类化合物的合成及其生物活性研究

以取代苯甲醛、取代吡啶和取代苯甲酸酯等为原料合成了 10种含硫杂环化合物 (其中 2a～ 2g化合物为国内外未见报道 ) .在合成过程中采用了超声波技术 ,极大地缩短了反应时间 ,提高了收率 .所得化合物的结构经IR ,1 HNMR ,MS和元素分析证实 .对其生物活性进行了初步测试 ,结果证明一些化合物具有良好的抑菌或杀菌作用 ,其中 2b ,2c ,2e ,2h ,2i和2j对大肠杆菌 ( 10 40 7号 )的抗菌效果与CET和SMZ相当 ;2b ,2c ,2f对草绿色链球菌 ( 112 3号 )的抗菌效果与CET和SMZ相当 .