甲烷在Li-Ln-MgO氧化物上催化氧化偶联

近年来,对天然气的综合利用已逐渐为人们所重视。甲烷氧化偶联制乙烯、乙烷这一新课题受到催化工作者愈来愈多的关注^[1~5]。本工作初步探讨了Li-Ln-MgO三元氧化物催化剂对甲烷氧化偶联反应的催化性能。添加稀土元素可使C₂的选择性、单收明显提高。本催化剂体系制备简单、原料便宜,值得进一步开发研究。     

First Total Synthesis of (±)-Aiphanol

Aiphanol was isolated from the seeds of Aiphanes aculeate Willd. (Arecaceae) collected in Peru and was reported to exhibit significant inhibitory activities against cyclooxyge- nases-1 and -2. The structure of aiphanol was elucidated by spectroscopic methods as an unprecedented stilbenolignan skeleton in which a stilbene moiety is linked to a phenylpropane unit through a dioxane bridge1. In our previous works the synthetic approach to 1,4-benzodioxane lignans were achieved2. Since aiphanol…     

A NOVEL ZWITTERIONIC SILANE COUPLING AGENT FOR NONTHROMBOGENIC BIOMATERIALS

A novel silane coupling agent bearing sulfobetaine group, N,N-diethyl-N-（3-sulfopropyl）-aminopropyl- trimethoxysilane （DESATS）, was first designed, synthesized and characterized. Its solution property was studied by means of dynamic light scattering. DESATS was successfully bonded onto the surface of the glass and proved by ESCA. Platelet adhesion assay in vitro indicated that the nonthrombogenicity of glass slide modified with DESATS is greatly improved.     

UV spectra and excitation delocalization in DNA: influence of the spectral width.

The singlet excited states of the model DNA duplex (dA)10.(dT)10 are studied. Calculations are performed in the exciton theory framework. Molecular dynamics calculations provide the duplex geometry. The dipolar coupling is determined using atomic transition charges. The monomer transition energies are simulated by Gaussian functions resembling the absorption bands of nucleosides in aqueous solutions. Most of the excited states are found to be delocalized over at least two bases and result from the mixing of different monomer states. Their properties are only weakly affected by conformational changes of the double helix. On average, the highest oscillator strength is carried by the upper eigenstates. The duplex absorption spectra are shifted a few nanometers to higher energies with respect to the spectra of noninteracting monomers. The states with larger spatial extent are located close to the maximum of the absorption spectrum.     

DIBUTYLTIN DILAURATE-CATALYZED DIISOCYANATE COUPLING- GRAFTING OF POLY(ETHYLENE GLYCOL) ONTO NANO-SILICA SURFACE THROUGH A ONE-STEP PROCEDURE

Grafting polymer glycols onto nano-silica surface through one-step procedure was investigated. The major characteristic of this procedure is that all the materials and reagents (silica, PEG, TDI, DBTDL, solvent) required for grafting were added simultaneously into the reaction vessel. TDI and DBTDL were used as coupling agent and catalyst, respectively.The products were characterized by FTIR, TGA, elemental analyses and TEM, giving evidence for successful grafting of PEG. Possible mechanism of this grafting was studied and two grafting processes were proposed. The process through which the grafting proceeds depends on the reaction temperature. Effect of molecular weight of PEG on grafting was also investigated.     

La0.7-xDyxSr0.3MnO3(0.00≤x≤0.70)的TCR研究

研究了La位Dy掺杂对La0.7-xDyxSr0.3MnO3(0.00≤x≤0.70)电阻温度系数(TCR)的影响.实验结果表明:Dy掺杂将引起电阻率曲线的急剧变化,导致出现大的TCR;随Dy掺杂的增加,TCR在x=0.30出现峰值,然后随掺杂量的增加逐步降低.体系出现大的TCR,来源于Dy掺杂引起的晶格畸变和额外磁性耦合.     

金属铜(Ⅱ)配合物催化2,6-二甲基苯酚氧化偶合反应的动力学研究

 合成了四种金属铜(Ⅱ)-四氮配合物,并用初始速率法研究了25 ℃时四种配合物催化H2O2氧化偶合2,6-二甲基苯酚生成3,3′,5,5′-四甲基联苯二醌反应的动力学. 结果表明此偶合反应符合Michaelis-Menten酶催化动力学,并由此获得了反应在不同配合物和不同pH值情况下的动力学参数k2和Km. 研究还发现不同的铜配合物其催化活性有不同的最适pH,具有较好电子共轭效应和合适刚柔性结构的铜配合物更有利于反应的进行. 对此催化反应的动力学机理研究发现,铜配合物的一级酸式电离中间物种是反应的主要催化活性物种. 质谱分析表明,此类铜配合物都能催化2,6-二甲基苯酚进行C-O偶合反应生成不同聚合度的高分子.     

Tandem Lewis acid catalyzed coupling/semipinacol rearrangement of allylic alcohol

Construction of the polyaryl quaternary unit through a ZnBr2 catalyzed tandem coupling/semipinacol rearrangement participated by allylic cations was reported for the first time.     

MOF-5负载Pd催化剂的制备及其催化性能初探

用水合肼还原Pd2+并将其负载在MOF-5上,制得了新型的Pd/MOF-5催化剂,采用XRD、氮吸附、SEM、TEM等多种手段对其进行了表征,催化剂的Pd纳米粒子尺寸在3~6nm之间。初步研究了该催化剂对催化卤代芳烃与芳基硼酸之间的Suzuki-Miyaura偶联反应的反应条件和催化性能,该催化体系具有反应条件温和、无需氮气保护和添加配体、产率优良等优点,催化剂循环利用5次仍然保持较高催化活性,平均产率超过90%。     

气相中W~+活化CO_2分解的自旋禁阻反应机理

用密度泛函理论中的UB3LYP方法,对W采用相对论校正赝势基组(SDD),对C、O采用6-311+G(3d)基组,研究了气相中不同自旋态W+活化CO2分解的反应机理.计算结果表明,W+活化CO2分解反应以六重态进入反应通道,经过六重态势能面到四重态势能面的系间窜越(ISC),最后产物WO+和CO以四重态离开反应通道.运用Harvey方法优化出最低能量交叉点(MECP),并计算了MECP处的自旋-轨道耦合(SOC)常数(494.95cm-1),势能面的交叉和在MECP处较强的自旋-轨道耦合作用降低了自旋禁阻反应能垒,为反应提供了一条低能反应路径,反应总放热量为122.33kJ.mol-1.