B2C3簇的结构和振动光谱的理论研究

用量子化学从头计算方法研究了Ｂ２Ｃ３簇各种可能的空间结构，计算了相应的振动光谱和结合能。对Ｂ２Ｃ３最稳定构型的电子结构进行了深入的分析和讨论。     

Force fields and vibrational spectroscopy: A discussion on status and future prospects

A start is given for a discussion about the use of force fields for describing and interpreting molecular geometries, relative energies and vibrational spectra. The development of modern, generic force fields, e.g. Class II force fields, has diminished the necessity for specific force fields, and they should be applied in far more cases than they are being used now.     

An ab initio and matrix isolation infrared study of the 1:1 C2H2–CHCl3 adduct

The details of weak C–Hπ interactions that control several inter and intramolecular structures have been studied experimentally and theoretically for the 1:1 C₂H₂–CHCl₃ adduct. The adduct was generated by depositing acetylene and chloroform in an argon matrix and a 1:1 complex of these species was identified using infrared spectroscopy. Formation of the adduct was evidenced by shifts in the vibrational frequencies compared to C₂H₂ and CHCl₃ species. The molecular structure, vibrational frequencies and stabilization energies of the complex were predicted at the MP2/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels. Both the computational and experimental data indicate that the C₂H₂–CHCl₃ complex has a weak hydrogen bond involving a C–Hπ interaction, where the C₂H₂ acts as a proton acceptor and the CHCl₃ as the proton donor. In addition, there also appears to be a secondary interaction between one of the chlorine atoms of CHCl₃ and a hydrogen in C₂H₂. The combination of the C–Hπ interaction and the secondary ClH interaction determines the structure and the energetics of the C₂H₂–CHCl₃ complex. In addition to the vibrational assignments for the C₂H₂–CHCl₃ complex we have also observed and assigned features owing to the proton accepting C₂H₂ submolecule in the acetylene dimer.     

Ab initio calculations of minimum-energy pathways of the nucleophilic addition of the H anion, LiH molecule and Li/H ion pair to acetylene and methylacetylene

Ab initio calculations were performed for special points of the minimal energy pathways (MEP) of the nucleophilic addition reactions of the isolated H⁻ anion, LiH molecule and Li⁺/H⁻ ion pair to acetylene (A) and methylacetylene (MA) molecules, proceeding in accordance (M) and against (aM) the Markovnikov's rule. All structural parameters were optimized using the restricted Hartree–Fock (RHF) method. For the addition of H⁻, the 6-31++G^* basis set was used and for the reactions of LiH and Li⁺/H⁻ the 6-31G^* basis set with the subsequent recalculation of single point energies, taking into account of electron correlation energy by means of the second-order Möller–Plesset perturbation theory at the MP2/6-31++G^** level. The results of calculations demonstrate, that the energy characteristics of both M- and aM-additions with H⁻ do not differ sufficiently (0.1–1.2 kcal/mol for the activation energies (ΔE_a) and the reaction heats (ΔQ)). The substitution of the H atom by the CH₃ group in A molecule results in practically the same values of ΔQ and ΔE_a. On the contrary, for the LiH molecule and Li⁺/H⁻ ionic pair, the M-addition is favorable (charge control). It is found that the presence of electrophile decreases the activation energy by 3–5 kcal/mol as compared with the addition of the isolated hydride ion H⁻.     

Ab initio MD simulations of a prototype of methyl chloride hydrolysis with explicit consideration of three water molecules: a comparison of MD trajectories with the IRC path

Ab initio molecular dynamics simulations at the Hartree-Fock/6-31G level of theory are performed on methyl chloride hydrolysis with explicit consideration of one solute and two solvent water molecules at a temperature of 298 K. The reaction involves the formation of a reactant complex and the energy surface to the transition state is found to be simple. Two types of trajectories toward the product are observed. In the first type, the system reaches an intermediate complex (complex-P1) region after two nearly concerted proton transfers involving the attacking water molecule and the solvent water molecules. These trajectories resemble the intrinsic reaction coordinate trajectory. The thermal motion of the atoms leads the system to another intermediate complex (complex-P2) region. A second type of trajectory is found in which the system reaches the complex-P2 region directly after the proton transfers. In both of these forward trajectories, back proton transfers lead the system to a final complex-F region which resembles protonated methanol. Received: 3 July 1998 / Accepted: 2 September 1998 / Published online: 15 February 1999     

Immunoaffinity chromatographic isolation of prostate-specific antigen from seminal plasma for capillary electrophoresis analysis of its isoforms

Prostate-specific antigen (PSA) concentration in serum has been the biomarker employed for prostate cancer diagnosis in the last two decades. However, new more specific biomarkers allowing a better differentiation of cancer from non-malignant prostate diseases are necessary. Glycosylation of PSA gives rise to different forms of the protein which can be separated into several isoforms by analytical techniques, such as CE. Because PSA glycosylation is influenced by pathological conditions, the CE pattern of PSA isoforms could be different in prostate cancer than in non-malignant prostate diseases. To study this CE pattern of PSA, prior purification of the protein from the biological fluid is mandatory. In this study an immunoaffinity chromatography method which allows PSA purification without altering the CE pattern is developed. An in-house prepared column produced with commercial anti-PSA antibodies is employed. The use of 1 M propionic acid as elution agent provides higher than 40% recovery of high purity PSA. CE analysis of PSA immunopurified from seminal plasma of a healthy individual shows the same 8 peaks as the commercially available PSA standard. Sample preparation only requires dilution with phosphate buffered saline prior to immunoaffinity purification. High repeatability for the sample preparation step was achieved (RSD% for percentage of corrected peak area in the range 0.6–5.3 for CE analysis of three independently purified seminal plasma aliquots compared to range 0.8–4.9 for a given aliquot analyzed three times by CE). IAC of five microliters seminal plasma provided enough PSA to achieve signal/noise ratio larger than 5 for the smallest CE isoforms.     

ClONO2及其异构体光解反应的从头算研究(Ⅱ)——ClONO2→ClO+NO2反应机理研究

用从头算方法讨论了大气臭氧层主要破坏物ClONO2在光照下分解反应途径:ClONO2→ClO+NO2的反应机理.该反应的2个过渡态ClO…NOO(TS2a)和OCI…NOO(TS2b)中TS2a能垒较高,始态难于越过如此高的势垒;TS2b势垒较低,而产物到过渡态TS2b的能垒也仅有1.20 eV,故预测该反应为一个可逆反应.     

NH_(2-3)~(0-1 )离解能等的高级ab initio计算与评价

FeiQi等人[1]最近对H2N－H、H2N －H的离解能以及NH3、NH2的电离能，用真空紫外光电离实验进行了重新测定，并同时得到了H2N－H 的离解能．他们还在QCISD（T）／6－311＋G（3df，ZP）／／MPZ（full）／6刁IG（d）水平（GZ理论的参考水平）上对这些数据及其它相关分子的某些性质     

聚芳醚酮单体结构与反应活性的研究

利用从头算ＲＨＦ方法研究了聚芳醚酮单体４，４’－对苯二酚、４，４’－联苯二酚及４，４’－二氟苯酮。结果表明，它们的苯环皆存在一定的扭转，首次给出联苯二酚全优化结构，其苯环二面角为５１．８°，活性稍强于对苯二酚，但引入更多的链支化活特点，含联苯基聚芳醚醚酮的链支化比不含联苯基的ＰＥＥＫ严重，故前者结晶性差，反应机理及实验还表明：前者凝胶化的浓硫酸溶液中存在一种羰基被极化后的红色阴离子。     

Molekulare Verbindungen mit SiAl4-, SiAl3- und GeAl4-Einheiten: Synthese und Struktur von Si(AlCl2 · OEt2)4, Ge(AlCl2 · OEt2)4 und HSi(Cp*AlBr)3

Molecular Compounds containing SiAl₄, SiAl₃, and GeAl₄ Units: Sythesis and Structure of Si(AlCl₂ · OEt₂)₄, Ge(AlCl₂ · OEt₂)₄, and HSi(Cp*AlBr)₃ In the scope of our investigations of the reactivity and the potential for synthesis of solutions of Al^I halides we performed reactions between these solutions and SiCp or GeCp, respectively. From these reactions we could isolate an unusual cluster with a central Al₁₄Si unit, described elsewhere, and the compounds Si(AlCl₂ · OEt₂)₄, Ge(AlCl₂ · OEt₂)₄, and HSi(Cp*AlBr)₃, which will be presented and discussed here. In these species the Si respectively the Ge atoms are connected to 4 respectively 3 Al atoms. This bonding results in strong negative polarized Si/Ge centres. The change of the polarization with respect to “normal” Si–R or Ge–R linking leads to a drastic weakening of the Si–R respectively the Ge–R bonds.