锂(100)面上H_2H+H反应动力学的理论研究

本文在H-Li(100)面吸附扩散的ab initio SCF势能面基础上构造了(H_2H+H)/Li(100)面相互作用的推广LEPS势能面,并用QCT方法研究了该体系的反应动力学行为。分析势能面特征得到:H_2在Li(100)面上的吸附无需活化能,H_2在Li(100)面上的解离吸附与吸附位及吸附模式密切相关,H_2的卧式解离比立式解离要容易得多。分析各种碰撞轨迹得到:低覆盖度下双氢原子的表面复合几率很小,H_2的表面解离几率受到H_2振动量子数的控制。本文构造了一种适合于动力学研究的气体-金属表面相互作用势能面,并且,动力学QCT计算结果能够对H_2表面活化的分子束实验作出合理的解释。     

多原子反应体系的高精度拟合势能面

本文介绍了近几年来我们组构建多原子反应体系的高精度拟合势能面的进展。我们基于神经网络(NN)方法,成功构建了多原子气相分子体系和气相分子在金属表面解离的一系列势能面。这些势能面的拟合精度相当高,并且经过了严格的量子动力学测试,能广泛应用到动力学研究中。我们还提出了一种新的置换不变势能面的拟合方法,即基本不变量神经网络方法(FI-NN)。基本不变量的使用极大地减少了神经网络输入层多项式的个数,有效提高了势能面的计算速度。     

Li_2H分子电子基态的从头算势能面及其振动激发态

用ab initio MRSDCI/6-311G(2 df,2 Pd)方法研究了Li_2H分子电子基态的势能面,计算了285个几何构型点的势能值,并采用Simons-Parr-Finlan展开式对这些势能值进行了拟合,得到均方差X~2等于4.64×10~(-6)(hartree~2).Li_2H分子电子基态的平衡几何构型为R_e=0.172nm,相似文献   

环丁酮光化学反应中S1/T1/S0交叉点的重要作用

势能面间的交叉在光化学反应中起着重要的作用 ,是由激发态反应物到基态产物发生无辐射跃迁的机制 .在本文中 ,我们用 CASSCF和态平均 CASSCF方法分别对环丁酮光化学反应的势能剖面及 S1,T1和 S0三个势能面间交叉进行了研究 .结果发现 ,基态和三态产物的形成是通过 S1,T1和 S0三个势能面交叉于同一区域 (称为 S1/T1/S0交叉点 )这一有效途径完成的 .　　60年代末 ,实验 [1－ 9]发现环丁酮和其它烷基酮 ,如丙酮、环戊酮的光化学反应机理很不一致 .主要体现在 ,i)环丁酮 (n,π态 )的α解离发生在 S1态势能面上 ,而其它烷基酮 (n,π态 …     

多原子分子在强飞秒激光场中的解离

强场化学是一个新的研究领域,分子在强激光场中解离则是该领域中的一个重要课题.本文阐述分子在强飞秒激光场(1013～1014 W·cm-2)中的解离规律以及我们所提出的场致解离(FAD)理论.在模型中我们考虑的是分子离子的解离,而且只考虑那些键轴平行于激光场方向的离子.此模型要求先计算出分子离子的缀饰势能面(Dressed PES),再计算键长随时间变化的准经典轨线(QCT).以甲烷、丙酮为例进行了实验和理论研究,理论计算的结果能很好地阐明观察到的实验结果.     

乙醇醛光解离机理的理论研究

采用多参考态方法, 在CASPT2//CASSCF/6-311+G(2df, 2p) 水平上计算了乙醇醛(HOCH2CHO)分子在三个最低电子态(S0、S1和T1)上驻点的电子结构和解离势能面。结合势能面交叉点,探讨了HOCH2CHO与波长有关的光解离机理,分析了可能的光解离产物。结果表明, 在实验光解波长240 – 400 nm的激发下,HOCH2CHO分子主要发生S1态上的解离反应或通过S0和S1态之间的振动相互作用驰豫到基态,随之发生基态解离反应。C-C键断裂生成基态光解产物HOCH2 (2A′)+ HCO (2A′)是最主要的反应途径;而在一定波长下,生成CH3OH + CO的基态协同反应、脱醛基氢及脱羟基通道都是能量上可行的反应途径。本文的计算结果和实验观察一致。     

氧硫化碳在230 nm光激发下的S(~3P)解离通道

在230nm激光激发下,氧硫化碳(OCS)分子迅速解离生成振动基态但高转动激发的CO(X~1∑_g~+,v=0,J=42-69)碎片,并通过共振增强多光子电离技术实现其离子化。通过检测处于J=56-69转动激发态CO碎片的离子速度聚焦影像,我们获得了各转动态CO碎片的速度分布和空间角度分布,其中包含了S(1D)+CO的单重态和S(~3P_J)+CO三重态解离通道的贡献。不同的转动态CO碎片对应三重态产物通道的量子产率略有不同,经加权平均我们得到230 nm附近光解OCS分子中S(3P)解离通道的量子产率为4.16%。结合高精度量化计算的OCS分子势能面和吸收截面的信息,我们获得了OCS光解的三重态解离机理,即基态OCS(X~1A')分子吸收一个光子激发到弯曲的A~1A'态之后,通过内转换跃迁回弯曲构型的基电子态,随后在C-S键断裂过程中与2~3A"(c~3A")态强烈耦合并沿后者势能面绝热解离。     

CO在Ni(100)面吸附模式的研究

本文首次将McGreery的推广LEPS法用于异核双原子分子的吸附势能面.设CO在Ni面上的吸附位置有3种(图1).取Sato参数为0.5,所得典型的势能面示于图2、图3.当C—O键平行于表面并接近Ni面上的3种吸附位置时,各势能面均与图2类似,先进入一势阱,然后越过势垒进入第二势阱.发生解离型C及O的原子吸附时,共有4种模式.各势能面上表征吸附的参数列于表1,吸附模式见图1.在4种吸附模式中最稳定的是C模式,即对角相邻5CN上的解离双原子吸附,R_(c-o)=6.65a.u.,它是R_(c-o)(平衡)=2.17a.u.的三倍多.当CO键与表面垂直且接近Ni面上3种吸附位置时所得势     

S3分子的结构与最可几解离过程理论研究

用量子化学从头算方法,计算得到了S3分子优化的几何结构(基态和几个低激发态);研究了其在C2v与Cs群对称性下的解离过程,给出两种群对称性下基态和激发态的势能曲面及等高投影图;在两种群对称性下均得到在相应势能曲面上的优化的解离路径.     

甲烷在O/Ni(100)表面上的反应动力学研究

甲烷在Ｏ／Ｎｉ（１００）表面上的反应动力学研究俞华根，程极源（中国科学院成都有机化学研究所，成都６１００１５）关键词甲烷，活化解离，预吸附氧，Ｎｉ（１００）表面，分子动力学，势能面甲烷在金属催化剂表面活化解离是重要的催化反应，受到了高度重视．近年来，...     

Theoretical Studies on Electronic Structures and Spectra for C80^n （D5d,C2v） Singlet

1INTRODUCTIONC80iscalledthemissingfullereneduetoitsinstabilityinkineticsandlowerLUMO-HOMOenergygap[1],aswellasthelowerabundanceintheexperimentandthedifficultyinsynthesis[1~5].However,thestableexistenceofcomplexLa2@-C80[2]stimulatestheresearchinterestinionsofC80.Zhang[3]performedtheoreticalstudiesonthestabi-lityandNMRspectraforC80isomers.Nakao[4]cal-culatedtheLUMO-HOMOenergygapofC80byusingabinitiomolecularorbital.Hennrich[5]syn-thesizedC80(D5)fromfullerenesootextractionbydHPLC.…     

Comparative Thermogravimetric Studies of Poly(ether-ketone/sulfone) Imides and Their Parent Polymers: I. Poly(ether-ketone/sulfone) ethylimide

Thermogravimetry (TG) was employed to study the thermal degradation kinetics of poly(etherketone/sulfone)ethylimide (PEK-IE and PES-IE). The corresponding decomposition activation energies and reaction orders were obtained and the comparison was made with their parent polymerspoly(ether-ketone/sulfone) with Cardo group (PEK-C and PES-C). The results show that the degradation activation energies of PEK-IE and PES-IE were lower than that of PEK-C and PES-C; and two stages of the degradation process were found for all the four polymers. For PEK-IE and PES-IE, the activation energies in the first decomposition stage are much lower than that in the second stage and the two stages can be taken as slow induction and fast degradation, whereas for PEK-C and PES-C the activation energies in the first decomposition stage are larger than that in the second stage, and the two stages can both be taken as two fast degradation stages. The decomposition mechanism of the two stages was also speculated.This revised version was published online in November 2005 with corrections to the Cover Date.     

手性二噁唑啉吡啶铁和镍配合物的制备与表征

Tridentate bis(oxazolinylpyridine)(1) reacted with nickel chloride or ferrous chloride in anhydrous ethanol to form bis(oxazolinylpyridine) Nickel(Ⅱ) and Iron(Ⅱ) complexes. The stable solid complexes were characterized with IR， UV， MS， XPS and elemental analysis. No stable complexes were formed with bidentate bis(oxazoline)(2) ins- tead of bis(oxazolinylpyridine).     

1-(2-噻唑)-3-(8-(5-对磺酸基苯基偶氮)喹啉)-三氮烯的合成及其与铜(Ⅱ)的显色反应

合成了新试剂1-(2-噻唑)-3-(8-(5-对磺酸基苯基偶氮)喹啉-三氮烯(TCPQT),并研究了其与Cu2+的显色反应。结果表明:在pH 7.5的磷酸盐缓冲溶液中,TCPQT与Cu2+形成摩尔比为1:1的紫红色络合物,该络合物在606.5nm处有一最大吸收峰,其表观摩尔吸光系数为3.36×105L.mol-1.cm-1,Cu2+的质量浓度在0～0.4μg/mL范围内符合比尔定律,相关系数r=0.9993。方法已用于测定食品中的微量铜。     

LiCl-Li2B4O7-H2O体系在298.15 K下热力学性质的等压研究

用等压法研究了298.15 K下LiCl-Li2B4O7-H2O体系在不同LiB4O7质量摩尔浓度时的等压平衡浓度,  水活度; 计算了LiCl和Li2B4O7混合盐溶液的渗透系数等热力学性质. 用298.15 K下的实验数据对Pitzer离子相互作用模型进行了参数化研究, 拟合求取了298.15 K下Pitzer离子相互作用参数, 用获得的参数计算了LiCl和Li2B4O7在LiCl-Li2B4O7-H2O体系中的活度系数. Pitzer模型计算的渗透系数值与实验结果一致.     

Synthesis of Derivatives of (4-Methyl-2-Quinolylthio)acetic and (4-Methyl-2-Quinolylthio)propionic Acids

An efficient synthesis has been developed for derivatives of (4-methyl-2-quinolylthio)acetic and (4-methyl-2-quinolylthio)propionic acids by the reaction of 4-methyl-2-thioxoquinoline with methyl methacrylate, the amide of methacrylic acid, acrylonitrile, ethyl bromoacetate, and ethyl acrylate. The hydrolysis of the resultant intermediates by (quinolylthio)acetic and (quinolylthio)propionic acids gave the corresponding acid products, which are also formed in the reaction of 4-methyl-2-thioxoquinoline with chloroacetic and acrylic acids. The reaction of 4-methyl-2-thioxoquinoline with allyl bromide was studied. The potassium permanganate oxidation of the resultant 2-allylthio-4-methylquinoline led to (4-methyl-2-quinolylthio)acetic acid.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 403–406, April, 2005.     

U(IV)/Ln(III) unexpected mixed site in polymetallic oxalato complexes. Part I. Substitution of Ln(III) for U(IV) from the new oxalate (NH4)2U2(C2O4)5·0.7H2O

A new ammonium uranium (IV) oxalate (NH₄)₂U₂(C₂O₄)₅·0.7H₂O (1) and three mixed uranium (IV)-lanthanide (III) oxalates, (N₂H₅)_2.6U_1.4M_0.6(C₂O₄)₅·xH₂O (M=Nd (2) and M=Sm (3)), Na_2.56U_1.44Nd_0.56(C₂O₄)₅·7.6H₂O (4) and Na₃UCe(C₂O₄)₅·10.4H₂O (5), have been prepared. The crystal structures of compounds 1, 4 and 5 have been determined by single-crystal X-ray diffraction. The crystal structures were solved by the direct methods and Fourier difference techniques, and refined by a least square method on the basis of F² for all unique reflections. Compounds 2 and 3 are isotypic with 1. Crystallographic data: 1, hexagonal, space group P6₃/mmc, a=19.177(3), c=12.728(4) Å, Z=6, R₁=0.0575 for 52 parameters with 1360 reflections with I?2σ(I); 2, hexagonal, space group P6₃/mmc, a=19.243(4), c=12.760(5) Å, Z=6; 3, hexagonal, space group P6₃/mmc, a=19.211(3), c=12.274(4) Å, Z=6; 4, orthorhombic, space group Pbcn, a=18.79(3), b=11.46(1), c=12.77(2) Å, Z=4, R₁=0.0511 for 183 parameters with 3026 reflections with I?2σ(I); 5, monoclinic, space group C2/c, a=18.878(6), b=11.684(4), c=12.932(4) Å, β=95.97(1)°, Z=4, R₁=0.0416 for 213 parameters with 4060 reflections with I?2σ(I). The honeycomb-like structure of the five compounds is built from the same three-dimensional arrangement of metallic and oxalate ions. Similar hexagonal rings of alternating metallic and oxalate ions form layers parallel to the (001) plane that are pillared by another oxalate ion. Indeed, some torsions or rotations of the bridging oxalate ligands led to modifications of the network symmetry. The monovalent cations and the water molecules occupy the hexagonal tunnels running down the [001] direction. Starting from the uranium (IV) compound A₂U₂(C₂O₄)₅·0.7H₂O with A=NH₄⁺ (1), the mixed U(IV)/Ln(III) oxalates are obtained by partial substitution of U(IV) by Ln(III) in a ten-coordinated site, the charge deficit being compensated by intercalation of supplementary monovalent ions within the tunnels. The distortion of the arrangement in the [001] direction for the Na-containing compounds allows the accommodation of a greater number of water molecules that insure an octahedral coordination of the Na atoms.     

SYNTHESES AND MASS SPECTRAL REARRANGEMENTS OF UNSATURATED BIS-SULPHIDES AND BIS-SULPHONES

Abstract

The synthesis of (E)- and (Z)-1.2-bis(p-fluorophenylsulphenyl)stilbenes (2a and 2b) and 1,2-bis(p-fluorophenylsulphonyl)stilbenes (3a and 3b) was carried out and their configurations were consistent with their stereospecific synthesis. The isomeric 1,1-bis(p-fluorophenylsulphenyl)- and 1,1-bis(p-fluorophenylsulphonyl)-2,2-bis(phenyl)ethylenes (8 and 9) were also synthesised and configurations were established by degradative oxidation. Mass spectral rearrangements of all these compounds were examined. Mass spectra of 1,1-bis-sulphide and 1,1-bis-sulphone bears close relationship with those of (E)- and (Z)-isomeric counterparts. Smiles-type rearrangement observed in 1,2-bis-sulphides was absent in 1,2-bis-sulphones. McLafferty-type rearrangement involving hydrogen migration, from aryl group was noticed in both bis-sulphides and bis-sulphones. Vinyl migration to the sulphone oxygen predominates over aryl migration in three isomeric bis-sulphones.     

(Phosphine)gold(I) Complexes of Benzenedithioles. Crystal structures of 1,2-benzenedithiolato-bis[triphenyl-phosphinegold(I)] and bis(triethylphosphine)gold(I) bis(1,2-benzenedithiolato)gold(III)

The reaction of 1,2- and 1,3-benzenedithiol C₆H₄(SH)₂ with chloro(phosphine)gold(I) complexes R₃PAuCl (R = Et, Ph) in the presence of triethylamine in tetrahydrofuran gives stable gold(I) complexes 1,2-C₆H₄(SAuPR₃)₂ [R = Et ( 1 ) and Ph ( 2 )] or 1,3-C₆H₄(SAuPPh₃)₂ ( 3 ), respectively, in high yield. The compounds have been characterized by analytical and NMR spectroscopic data. From the reaction of 1,2-C₆H(SH)₂ with Et₃P? AuCl a by-product [(Et₃P)₂Au]⁺ [Au(1,2? C₆H₄S₂)₂]^? ( 4 ) has also been isolated in low yield. The crystal structures of compounds 2 and 4 have been determined by single crystal X-ray diffraction. The gold(I) atoms in complex 2 are two-coordinate with bond angles S? Au? P of 175.2(1) and 159.5(1)°, Au? S bond distances of 2.304(1) and 2.321(1) å, and a short Au…?Au contact of 3.145(1) Å. The gold(I) atom in the cation of complex 4 is also linearly two-coordinate with a P? Au? P angle of 170.1(1) Å and Au? P distances of 2.296(3) and 2.298(3) Å. The geometry of the anion in 4 shows a square-planar coordination of gold(III) by two chelating 1,2-benzenedithiolate ligands with Au? S distances between 2.299(3) and 2.312(3) Å (for two crystallographically independent, centrosymmetrical anions in the unit cell).     

Mo（W）－Cu（Ag）－S原子簇化合物的研究现状

本文在研究Ｍｏ（Ｗ）－Ｃｕ（Ａｇ）－Ｓ原子簇化合物的低热固态合成化学基础上，详细地对该类簇合物进行了归纳，从中提出：１．（Ｍ＝Ｍｏ，Ｗ；ｎ＝２，３，４）作为配体中心．２．氧原子在簇合物中仅作为端基，不参与同其他金属成键．３．单个ＭＳ４（Ｍ＝Ｍｏ，Ｗ）基团最多只能键合六个Ｃｕ（Ａｇ）原子，即最大核数为七．４．迄今为止所有Ｍｏ（Ｗ）－Ｃｕ－Ｓ原子簇化合物中Ｃｕ均为＋１价．５．预计合低价态Ｍｏ（Ｗ）的这类簇合物将会有很大进展．