C2D2和C2H2分子键-键耦合研究

采用Morse根于描述C_2D_2分子中C－D键的伸缩振动，用谐振子描述C－C键伸缩振动，更新构造了C2D2分子的振动哈密顿，自行设计了非线性最小二乘拟合程序，并用它对C2D2分子的伸缩振动能级进行拟合，得到了基本的势能参数．理论计算与实验结果符合得很好，拟会的标准差为1.14cm－1；利用这些参数进一步计算了C2H2和C2D2的振动能级．     

Synthesis of 2-deamino- and 2-deamino-2-nitroactinomycin D

A single step synthesis of 2-deaminoactinomycin D ( 3a ) and 2-deamino-2-nitroactinomycin D ( 2a ) arising from actinomycin D ( 1a, AMD ) is reported. Structural confirmation was made by nmr, ir and chemical conversion to known materials.     

Zur Kristallstruktur von Rb2C2 und Cs2C2

On the Crystal Structure of Rb₂C₂ and Cs₂C₂ By reaction of rubidium or caesium solved in liquid ammonia with acetylene AC₂H with A = Rb, Cs was obtained, which was subsequently converted into the binary acetylide A₂C₂ in vacuum at temperatures of 520 K (Rb₂C₂) and 470 K (Cs₂C₂) using a surplus of the respective alkali metal. The crystal structures of the very air sensitive compounds were solved and refined by a combination of both neutron and X‐ray powder diffraction data. Rb₂C₂ as well as Cs₂C₂ coexist in two modifications. The hexagonal modification (P 6 2m, Z = 3) crystallises in the known Na₂O₂ structure type with two crystallographic independent sites for the C₂^2– dumbbells. For the orthorhombic modification (Pnma, Z = 4) a new structure type was found, which is related to the PbCl₂ structure type with ordered C₂^2– dumbbells occupying the Pb sites. Temperature dependent investigations between 4 K and the decomposition temperature by the means of neutron and X‐ray powder diffraction resulted in a very complex dynamic disorder of the C₂ dumbbells, which is still not completely understood. The frequencies of the C–C stretching vibration determined by the help of Raman spectroscopy fit nicely to the results obtained for other alkali metal acetylides and alkali metal hydrogen acetylides. These results seem to indicate that the electronegativity of the alkali metal has a strong influence on the frequency of the C–C stretching vibration.     

Reaction of [2-(SiH3)C6H4]2SiH2 with Ni(Et2PCH2CH2PEt2)(PEt3)2: characterization of eta2-(Si-H)Ni and NiIV-H complexes

The reaction of (2-SiH3C6H4)2SiH2 with Ni(Et2PCH2CH2PEt2)(PEt3)2 afforded a new silylnickel complex, which, in the solid state, was determined to be a bis(silyl)eta2-(Si-H)nickel complex, the first example of eta2-(Si-H)nickel complex by single-crystal X-ray analysis. Variable-temperature NMR spectroscopy revealed fluxional behavior of the complex in solution; at room temperature, exchange of five hydrogens (two SiH2 and one hydrogen bound to nickel) was observed, while at -80 degrees C the exchange of hydrogens appeared frozen to adopt a tris(silyl)(hydrido)nickel(IV) structure, which was confirmed by theoretical calculation. The latter complex is the first example of hydridonickel(IV) complex.     

Elektrochemische Deintercalation von Ag2PbO2

Electrochemical Deintercalation of Ag₂PbO₂ Ag₂PbO₂ was electrochemically deintercalated. The electrochemical reactions were studied in a two electrode swagelock teflon laboratory cell. A silver metal foil was used as negative electrode, and a pellet of the educt phase Ag₂PbO₂ (diameter 9 mm, thickness ca. 0.5 mm) without any graphite or binder was used as positive electrode. Silvernitrate, dissolved in acetonitrile (0.1 mol), was applied as liquid electrolyte. The electrotitration was carried out with a constant charge density of 6 μA/cm². Periods of working potential (48 h) alternated with periods of the open cell potential (3 h). The development of the cell voltage at decreasing silver content shows a continuous change of slope without any extended plateau. The Ag₂PbO₂ cell was totally charged, and the resulting product of deintercalation was proven to be binary PbO₂ in the stable α‐modification. The Rietveld evaluation of the powder diffraction data of intermediate deintercalated phases gave conclusive support to a two phase mode mechanism of deintercalation during which α‐PbO₂ was continuously separated without forming Ag_xPbO₂ solid solutions.     

Kinetics of O2(a1Deltag) and I(2P1/2) in the photochemistry of N2O/I2 mixtures

The recent demonstration of a discharge-driven oxygen-iodine laser has generated renewed interest in the kinetics of iodine interacting with electronically excited O2 and atomic O. Kinetic measurements that are of relevance to the laser have been carried out using 193 nm pulsed laser photolysis of N2O/I2/CO2 mixtures. Singlet oxygen was generated in this system by the reaction O(1D)+N2O-->O2(a1Deltag, X3Sigma-g)+N2. The fraction of electronically excited O2 produced by this channel was shown to be >0.9. The secondary photochemistry of the N2O/I2/CO2 system was characterized by monitoring the time histories of I(2P1/2), I2, IO, and O2(a). Kinetic modeling of these data was used to determine the rate constant for the deactivation of I(2P1/2) by O(3P) (k=(1.2+/-0.1)x10(-11) cm3 s(-1)). Quenching of I(2P1/2) by O(3P) is suppressed in the discharge-driven laser by using NO2 to scavenge the O atoms. The reaction O(3P)+NO2-->O2+NO is sufficiently exothermic for the production of O2(a), and it has been speculated that this channel may be significant in the laser excitation kinetics. Photolysis of NO2 was used to probe this reaction. O2(a) was not detected, and an upper bound of <0.1 for its production in the reaction of O(3P) or O(1D) with NO2 was established.     

FeCl2-K2MoS4体系电催化还原乙炔为乙烯

采用控电位电解、循环伏安法和交流阻抗法研究了FeCl₂-K₂MoS₄体系对乙炔在石墨电极上还原为乙烯的电催化活性及反应机理。实验结果表明,当石墨阴极的电位控制在-1.50V(vs.SCE)时,FeCl₂+K₂MoS₄的DMF溶液对C₂H₂还原为C₂H₄表现出明显的电催化活性和高的选择性。在-0.5～-1.0V时Mo(Ⅵ)还原为Mo(Ⅴ);在按连串的电子传递机理进行的Mo(Ⅴ)→Mo(Ⅲ)反应的电位区间(-1.0～-1.50V)溶液中所形成的络合品种传递电子的能力更强。Mo(Ⅲ)可能是络合物的电活性成分。     

A heterometal single-molecule magnet of [MnIII2NiII2Cl2(salpa)2

The tetranuclear complex [MnIII2NiII2Cl2(salpa)2] (salpa = N-(2-hydroxybenzyl)-3-amino-1-propanol) has a spin ground state of S = 6 and was confirmed to be an SMM based on a steplike feature of the magnetization hysteresis loop at 0.55 K.     

Detection of H2O2 released from TiO2 photocatalyst to air.

H2O2 generated and released from TiO2 photocatalysts to the gas phase was detected. A flow-through cell packed with TiO2-coated glass beads was irradiated with UV light, and the gas flowing out of the cell was flushed through a collecting solution containing 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulforic acid) diammonium salt (ABTS) and peroxidase. Oxidative coloration of ABTS was observed only in the absence of catalase, indicating the presence of H2O2 in the gas. The quantum yield of the H2O2 generation was estimated to be > 1 x 10(-7). The detected amount of H2O2 decreased as the TiO2 thickness decreased. H2O2 was not detected when dry air or nitrogen was used.     

Functional polymers. XVI. Synthesis and polymerization of 2(2-hydroxy-5-isopropenylphenyl)-2H-benzotriazole and a new synthesis of 2(2-hydroxy-5-vinylphenyl)2H-benzotriazole

2(2-Hydroxy-5-isopropenylphenyl)2H-benzotriazole was synthesized in 40% overall yield starting from o-nitroaniline. Diazotization in aqueous hydrochloric acid gave o-nitrophenyl diazonium chloride which was condensed with p-hydroxyacetophenone; the azo compound was reduced to 2(2-hydroxy-5-acetylphenyl) 2H-benzotriazole with zinc powder in sodium hydroxide solution and the 2-hydroxy group of the compound was acetylated. Treatment of the acetyl compound with methyl Grignard reagent resulted in the methylation of the 5-acetyl group to 2[2-acetoxy-5(2-hydroxy-2-propyl)phenyl]2H-benzotriazole which was then dehydrated with potassium hydrogen sulfate to the desired 2(2-hydroxy-5-isopropenylphenyl)2H-benzotriazole. This monomer did not homopolymerize, but was copolymerized readily with styrene, methyl methacrylate, and n-butyl acrylate with azobisisobutyronitrile as the initiator. 2(2-Acetoxy-5-acetylphenyl)2H-benzotriazole was also reduced with sodium borohydride to form 2[2-acetoxy-5-(1-hydroxyethyl)phenyl]2H-benzotriazole which was dehydrated and hydrolyzed to the known 2(2-hydroxy-5-vinylphenyl)-2H-benzotriazole. This route provides a novel and simpler synthesis of 2(2-hydroxy-5-vinylphenyl)2H-benzotriazole.     

Ni(Et2PCH2NMeCH2PEt2)2]2+ as a functional model for hydrogenases

The reaction of Et(2)PCH(2)N(Me)CH(2)PEt(2) (PNP) with [Ni(CH(3)CN)(6)](BF(4))(2) results in the formation of [Ni(PNP)(2)](BF(4))(2), which possesses both hydride- and proton-acceptor sites. This complex is an electrocatalyst for the oxidation of hydrogen to protons, and stoichiometric reaction with hydrogen forms [HNi(PNP)(PNHP)](BF(4))(2), in which a hydride ligand is bound to Ni and a proton is bound to a pendant N atom of one PNP ligand. The free energy associated with this reaction has been calculated to be -5 kcal/mol using a thermodynamic cycle. The hydride ligand and the NH proton undergo rapid intramolecular exchange with each other and intermolecular exchange with protons in solution. [HNi(PNP)(PNHP)](BF(4))(2) undergoes reversible deprotonation to form [HNi(PNP)(2)](BF(4)) in acetonitrile solutions (pK(a) = 10.6). A convenient synthetic route to the PF(6)(-) salt of this hydride involves the reaction of PNP with Ni(COD)(2) to form Ni(PNP)(2), followed by protonation with NH(4)PF(6). A pK(a) of value of 22.2 was measured for this hydride. This value, together with the half-wave potentials of [Ni(PNP)(2)](BF(4))(2), was used to calculate homolytic and heterolytic Ni-H bond dissociation free energies of 55 and 66 kcal/mol, respectively, for [HNi(PNP)(2)](PF(6)). Oxidation of [HNi(PNP)(2)](PF(6)) has been studied by cyclic voltammetry, and the results are consistent with a rapid migration of the proton from the Ni atom of the resulting [HNi(PNP)(2)](2+) cation to the N atom to form [Ni(PNP)(PNHP)](2+). Estimates of the pK(a) values of the NiH and NH protons of these two isomers indicate that proton migration from Ni to N should be favorable by 1-2 pK(a) units. Cyclic voltammetry and proton exchange studies of [HNi(depp)(2)](PF(6)) (where depp is Et(2)PCH(2)CH(2)CH(2)PEt(2)) are also presented as control experiments that support the important role of the bridging N atom of the PNP ligand in the proton exchange reactions observed for the various Ni complexes containing the PNP ligand. Similarly, structural studies of [Ni(PNBuP)(2)](BF(4))(2) and [Ni(PNP)(dmpm)](BF(4))(2) (where PNBuP is Et(2)PCH(2)N(Bu)CH(2)PEt(2) and dmpm is Me(2)PCH(2)PMe(2)) illustrate the importance of tetrahedral distortions about Ni in determining the hydride acceptor ability of Ni(II) complexes.     

Synthesis of 2-deoxy-2-c-alkyl glycal and glycopyranosides from 2-hydroxy glycal ester

A method to convert 2-hydroxy glycal ester to the corresponding 2-deoxy-2-C-alkyl glycal in a facile manner, through key reactions including (i) C-allylation at C-1, (ii) Wittig reaction, and (iii) Cope rearrangement of a 1,5-diene derivative, is reported. The α-anomer of the 1,5-diene derivative underwent Cope rearrangement to afford 2-deoxy-2-C-glycal derivative, whereas the β-anomer was found to be unreactive. Employing this sequence, 3,4,6-tri-O-benzyl-2-O-acetyl-1,5-anhydro-d-arabino-hex-1-enitol was transformed to 3,4,6-tri-O-benzyl-2-deoxy-2-C-alkyl-1,5-anhydro-D-arabino-hex-1-enitol. 2-Deoxy-2-C-alkyl glycal derivative is a suitable glycosyl donor to prepare 2-deoxy-2-C-alkyl glycosides, mediated through haloglycosylation and a subsequent dehalogenation. A number of 2-deoxy-2-C-alkyl glycosides, with both glycosyl and nonglycosyl moieties at the reducing end, are thus prepared from the glycal.     

Atrazine toxicity reduction following H2O2/TiO2- photocatalyzed reaction and comparison with H2O2- photolytic reaction

An atrazine photodegradation study carried out by a Q-Panel suntest apparatus is reported in this work. H2O2/TiO2 photocatalyzed reaction yield and parameters (time, irradiance, temperature, H2O2 (40%) volume, TiO2 amount) were exactly determined relating to the used atrazine concentration. An experimental kinetic study was performed to establish the reaction order in fixed conditions. Using a biosensor method, 10(-4) M Atrazine solution toxicity and final photocatalytic reaction solution toxicity were quantitatively determined. A consistent toxicity decrease was observed on passing from the analyte to the products of the photocatalytic reaction. An analogous photolytic reaction carried out in absence of TiO2, but in the same experimental conditions of time, irradiance, temperature and H2O2 volume, brings to a toxicity increase.     

Studies on TiO2/SiO2 and Pd/TiO2/SiO2 Catalysts in Photoreduction of CO2 with H2O to Methanol

The development of industry induced a massive increase in the emission of carbon dioxide into the atmosphere. A large amount of CO₂ and its general availability causes that it could be a cheap reactant in a reaction that runs in a way similar to photosynthesis in plants. Pure TiO₂ and metal doped TiO₂ are the most studied semiconductor catalysts for photoreduction of CO₂. The TiO₂/SiO₂ and Pd/TiO₂/SiO₂ catalysts were prepared and studied by temperature-programmed desorption, X-ray diffraction analysis, SEM-EDS, temperature-programmed reduction and then used for the methanol synthesis. The photoactivity of Pd/TiO₂/SiO₂ catalysts in the reduction of CO₂ with H₂O was tested at room temperature using photoreactor equipped with 16 lamps. The wavelength was characteristic of near ultraviolet. Post-reaction products were identified with gas chromatograph equipped with the flame ionization detector. Pd doping made the catalysts photoactive and the photoactivity of catalysts was changing as follows: 1%Pd/5%TiO₂/SiO₂ > 1% Pd/10% TiO₂/SiO₂ > 1% Pd/15% TiO₂/SiO₂. Optimum ultraviolet radiation time in the photoreduction of CO₂ to methanol was 7 h. An addition of Pd does not change the surface of the carrier.     

Cerium-modified Ni-La_2O_3/ZrO_2 for CO_2 methanation

The key point in CO_2 methanation is to improve the activity at low temperature and the stability.For this purpose,a new cerium-modified Ni-La_2O_3/ZrO_2 catalyst was prepared using La_(1-x)Ce_xNiO_3/ZrO_2 with perovskite phase as the precursor,which was obtained by citrate complexation combined with an impregnation method.The resulting catalyst was characterized through Nitrogen adsorption and desorption,X-ray diffraction (XRD),Transmission electron microscopy (TEM),Hydrogen temperature programmed reduction (H_2-)TPR),Temperature-programmed desorption of CO_2 (CO_2-TPD) and that of H_2 (H_2-TPD),and X-ray photoelectron spectroscopy (XPS) techniques,and the catalytic performances for CO_2 methanation was investigated.Cerium modification could improve the effective activation of CO_2,thus enhancing the activity at low temperature for CO_2 methanation.The metal Ni nanoparticles prepared using this method were highly dispersed and showed excellent resistance to sintering,leading to very good stability,which could be attributed to the following:Ni nanoparticles could be confined by cerium-modified La_2O_3;La_2O_3could be confined by the cerium ions at the La_2O_3/ZrO_2 interface;and the cerium ions were confined by ZrO_2.     

Reaction of silanes in supercritical CO2 with TiO2 and Al2O3

Infrared spectroscopy was used to investigate the reaction of silanes with TiO2 and Al2O3 using supercritical CO2 (Sc-CO2) as a solvent. It was found that contact of Sc-CO2 with TiO2 leads to partial removal of the water layer and to the formation of carbonate, bicarbonate, and carboxylate species on the surface. Although these carbonate species are weakly bound to the TiO2 surface and can be removed by a N2 purge, they poison the surface, resulting in a lower level of reaction of silanes with TiO2. Specifically, the amount of hexamethyldisilazane adsorbed on TiO2 is about 10% of the value obtained when the reaction is performed from the gas phase. This is not unique to TiO2, as the formation of carbonate species also occurs upon contact of Al2O3 with Sc-CO2 and this leads to a lower level of reaction with hexamethyldisilazane. This is in contrast to reactions of silanes on SiO2 where Sc-CO2 has several advantages over conventional gaseous or nonaqueous methods. As a result, caution needs to be applied when using Sc-CO2 as a solvent for silanization reactions on oxides other than SiO2.     

CRTA Study of the Reduction of UO2F2 into UO2 by Dry H2

The reduction of UO₂F₂ by dry H₂ was studied by Controlled Rate EGA, with a special set-up operating under a gas flow under atmospheric pressure. At the constant transformation rate selected, this reduction apparently takes place in one main step, around 450°C (for a total duration of 100 h), followed by a small exothermic step. The final product is a stoichiometric, well crystallized UO₂. XRD analysis shows the occurrence of two successive intermediates of which one has a structure close to that of UO₂, but with interstitial fluorine atoms. This revised version was published online in August 2006 with corrections to the Cover Date.     

二聚体有机锡配合物{[n-Bu2SnO2CCH(CS2NEt2)2]2O}2的合成、表征及晶体结构

近年来,有机锡(Ⅳ)的羧酸配合物因其具有很强的生物活性以及丰富的结构类型备受人们的重视．实验证明,它们的生物活性与锡原子的配位形式有关,而中心锡原子的配位形式决定于直接与锡原子相连的烃基的结构和羧酸基配体的类型。     

Iridium complex-catalyzed highly selective cross [2 + 2 + 2] cycloaddition of two different monoynes: 2:1 coupling versus 1:2 coupling

[reaction: see text] Highly selective cross [2 + 2 + 2] cycloaddition of two different monoynes is achieved by using a catalytic amount of [Ir(cod)Cl](2) and ligand. The ligand had a considerable effect on the reaction. When 1,2-bis(diphenylphosphino)ethane was used, two molecules of dimethyl acetylenedicarboxylate (DMAD) reacted with one molecule of a monoyne to give the 2:1 coupling product. When 1,2-bis(dipentafluorophenylphosphino)ethane was used instead of dppe, one molecule of DMAD reacted with two molecules of a monoyne to give the 1:2 coupling product.     

新型层状磷酸铝[Al6P8O32][(C2H5)2NHCH2CH2NH3]2·[C2H5NH2CH2CH2NH2C2H5] 的合成、表征及其共模板作用

在溶剂热体系中,以N,N-二乙基乙二胺为结构导向剂,合成了Al/P为3/4的层状磷酸铝[Al6P8O32][(C2H5)2NHCH2CH2NH3]2·[C2H5NH2CH2CH2NH2C2H5]单晶,并通过X射线单晶衍射结构分析.XRD,ICP,元素分析,差热-热重分析等手段进行了表征.该化合物属单斜晶系,P2(1)/c空间群,晶胞参数:a=0.90945(2)nm,b=1.46424(4)nm,c=1.87572(5)nm,β=102.672(2)°,Z=4.其阴离子层由AlO4四面体和PO3(=O)四面体单元交替连接构成,形成四、六、八元环拓扑结构,无机层以ABAB方式堆积,两种质子化的有机胺分子N,N-二乙基乙二胺及其重排产物N,N′-二乙基乙二胺填充在层间.用分子动力学模拟方法,考察了标题化合物中有机胺与无机层间的相互作用,讨论了这两种有机胺的共模板作用.