C_4O_2S_2~m-(m=0,1,2,3,4)相对稳定性的从头算研究

在ＲＨＦ（基离子在ＵＨＦ和ＲＯＨＦ）／６－３１Ｇ、６－３１Ｇ、６－３１＋Ｇ和６－３１＋Ｇ水平优化得到Ｃ４Ｏ２Ｓ２ｍ－（ｍ＝０,１,２,３,４）的平衡几何构型,发现从中性分子到－４价离子经历了一个从非芳香性体系到芳香性体系再到反芳香性体系的有趣变化过程,它们的稳定性顺序为：Ｃ４Ｏ２Ｓ２－·＞Ｃ４Ｏ２Ｓ２２－＞Ｃ４Ｏ２Ｓ２＞Ｃ４Ｏ２Ｓ２３－·＞Ｃ４Ｏ２Ｓ２４－．     

C_4S_4~(m-)(m=0,1,2,3,4)的从头算研究2.成键状况、电离势和振动频率

在ＲＨＦ（基离子在ＵＨＦ）／６－３１Ｇ,６－３１Ｇ＊和６－３１＋Ｇ水平用从头算和Ｂｏｙｓ定域化方法计算了Ｃ４Ｓ４ｍ－（ｍ＝０,１,２,３,４）的电子结构、电离势和定域化分子轨道。讨论了其成键特征和电离势与ΔＥＳＣＦ的关系。在６－３１Ｇ水平用ａｂｉｎｉｔｉｏ解析方法计算它们的谐振动频率。电子结构计算结果和Ｂｏｙｓ定域化分子轨道及振动分析结果与优化的平衡几何和相对稳定性相一致     

H＋NF_2→NF（α）＋HF反应的从头算研究

本文用量子化学从头算法对Ｈ＋ＮＦ_２→ＮＦ（α）＋ＨＦ反应进行了理论研究，采用ＭＰ_２（ＦＵＬＬ）／６－３１Ｇ（ｄ）方法计算了反应物、产物、中间体和过渡态的构型参数和振动频率，然后用Ｇａｕｓｓｉａｎ－２理论计算了各物种的精确能量，计算结果表明：反应在单重态势能面上进行，电子激发态ＮＦ（α）通过复合－消除机理产生，用Ｇ２理论计算２９８Ｋ下反应的焓变为－１１９．４ｋＪ／ｍｏｌ，过渡态比反应物能量低９８．４ｋＪ／ｍｏｌ．中间体ＨＮＦ２是势能面的最低点，比反应物的能量低３１３．５ｋＪ／ｍｏｌ．     

1,2—C4H6→2—C4H6异构化反应机理的理论研究

采用自洽场分子轨道ＵＨＦ／６－３１Ｇ＊＊从头算法，研究了１，２－Ｃ４Ｈ６→２－Ｃ４Ｈ６异构化反应机理，优化了基态势能面上反应物，过渡态，中间体和产物的几何构型，并对各驻点能量进行了零点能校准。结果表明该反应经历了一个１－甲基环丙烯生产产物比较两步氢迁移反应历程更易发生。     

（四甲基二硅撑）双（3－三甲硅基环戊二烯基）－四羰基二铁的反应性

标题化合物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η￣５－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２］_２／（μ－ＣＯ）_２（Ａ）分子中的Ｆｅ－Ｆｅ键被钠汞齐还原断裂，生成相应的双铁负离子，分别与ＭｅＣＯＣｌ、ＰｈＣＯＣｌ、ＰｈＣＨ_２Ｃｌ、ＣｌＣＨ_２ＣＯＯＣ_２Ｈ_５和Ｐｈ_３ＳｎＣｌ进行亲核取代反应，生成在铁原子上引入相应取代基的产物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η￣５－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２Ｒ］_２（Ｒ：ＭｅＣＯ（１），ＰｈＣＯ（２），ＰｈＣＨ_２（３），ＣＨ_２ＣＯＯＣ_２Ｈ_５（４），Ｐｈ_３Ｓｎ（５），Ｉ（６））。Ａ在氯仿中与碘反应，得到Ｆｅ－Ｆｅ断裂的双铁碘化物，但在苯中与过量碘反应，则得到Ｆｅ－Ｉ－Ｆｅ桥联的离子型化合物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η￣５－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２］_２Ｉ·Ｉ（７）。化合物６的晶体和分子结构经Ｘ射线衍射测定，６属单斜晶系，Ｐ２１／ｃ空间群，ａ＝１．７２１７（４）ｎｍ，ｂ＝０．７７５３（２）ｎｍ，Ｃ＝１．３６２９（７）ｎｍ，β＝１０３．８０（３）°，Ｖ＝１．７６７（２）ｎｍ３，Ｚ＝４，Ｄｃ＝１．６２９９·ｃｍ－１，最终偏差因子Ｒ＝０．０５４。     

高电势铁硫蛋白的模型化合物：2,4,6—三苯基苯硫酚的4Fe4S簇合 …

新型簇合物（ｎ－Ｂｕ４Ｎ）２「Ｆｅ４Ｓ４（ｔｐｂｔ）４」（ｔｐｂｔ－２，４，６－三苯基苯硫酚基）通过２，４，６－三苯基苯硫酚和（ｎ－Ｂｕ４Ｎ）２「Ｆｅ４Ｓ４９Ｓ－ｔ－Ｂｕ０４」在ＤＭＦ中进行配体交换反应合成得到。该簇合物在ＣＨ３ＣＮ溶液中的「Ｆｅ４Ｓ４」＾３＋／２＋和「Ｆｅ４Ｓ４」＾２＋１／＋的氧化还原电位分别为－０．１４和－１．３１ＶｖｓＳＣＥ。     

HCO＋HCN→HCHO＋CN反应机理研究

用ａｂｉｎｉｔｉｏ方法在ＵＨＦ／６－３１Ｇ基组上研究了ＨＣＯ　＋ＨＣＮ→ＨＣＨＯ＋ＣＮ　反应的反应机理。经寻找反应的过渡态和计算内禀反应坐标（ＩＲＣ）表明，该反应经一过渡态而形成产物，具有较宽的位垒，并属于后位垒反应。用ＵＭＰ２∥６－３１Ｇ方法计算的活化位垒为１４９．６０２ｋＪ／ｍｏｌ，与实验值（１４３．００１ｋＪ／ｍｏｌ）相当一致。     

ClnAlNHn和HnAlNHn(n=1～3)的振动光谱与化学键性质的研究

用从头计算分子轨道法和密度泛函理论，在ＨＦ／６－３１Ｇ＊和Ｂ３ＬＹＰ／６－３１Ｇ＊水平上对ＣｌｎＡｌＮＨｎ和ＨａＡｌＮＨｎ（ｎ＝１～３）及其碎片分子的几何构型、电子结构、振动光谱和化学热力学性质进行了理论研究。结果表明，优化几何参数与实验值相。ＣｌＡｌＮＨ２和Ｈ２ＡｌＮＨ２分子中，Ａｌ－Ｎ键为由一个σ键和一个π键组成的双重键，旋转势垒分别为３４．１０和５４．３５ＫＪ．ｍｏｌ＾－１，而Ｃｌ３ＡｌＮＨ     

在小硅化物SiX^m4（X=H,He,Li,Be,O,F,Ne,Na,Mg,S,Cl,Ar;m=0,…

用从头算方法，在ＨＦ／ＳＴＯ－３Ｇ、ＨＦ／３－２１Ｇ和ＨＦ／６－３１Ｇ水平上研究了小硅化物ＳｉＸ＾ｍ４的成键倾向性。计算结果表明，所研究的分子势能曲线均有稳定的极小值（ＳｉＬｉ４除外）。与已知的稳定分子ＳｉＨ１、ＳｉＦ４和ＳｉＣｌ４比较，含惰性元素的未知分子ＳｉＨｅ＾４＋４、ＳｉＮｅ＾４＋４和ＳｉＡｒ＾４＋４比含碱金属和碱土金属的未知分子ＳｉＬＩ４、ＳｉＮａ４、ＳｉＢｅ＾４＋４和ＳｉＭｇ＾４＋４有     

超价化合物NLi4^n＋和OLi4^n＋电子结构和性质

以６－３１Ｇ＾＊基组利用ＨＦ、ＭＰ２和ＤＦＴ方法优化了超价化合物ＮＬｉ４＾ｎ＋和ＯＬｉ４＾ｎ－的几何构型。研究结果表明，ＭＰ２和ＤＦＴ法计算出的ＯＬｉ４分子解离出Ｌｉ和Ｌｉ２的反应能与已有的实验值吻合，对于ＮＬｉ４分子，得到其解离出Ｌｉ和Ｌｉ２的反应能分别为１９１．７８和５１５．３７ｋＪ／ｍｏｌ（ＭＰ２值）。并预测了ＯＬｉ４＾ｎ＋和ＮＬｉ４＾ｎ＋分子的基振动频率。     

Confluenines A–F, N-oxidized l-isoleucine derivatives from the edible mushroom Albatrellus confluens

The phytochemical study of the fruiting bodies of Albatrellus confluens afforded three pairs of new N-Oxidized l-Isoleucine derivatives epimers, confluenines A–F (1–6). The structures of these compounds were deduced using spectroscopic techniques, and the absolute configurations of the compounds were assigned by comparison between experimental and theoretical NMR and ECD data, respectively. Putative biosynthetic pathways toward the oxime, hydroxamate moieties and epimers were discussed. Compounds 5 and 6 exhibited weak antimicrobial activities against Staphylococcus aureus with MIC₉₀ values at 29.3?μg/mL and 56.7?μg/mL, respectively.     

Theoretical calculation of the low laying electronic states of the molecular ion RbH+

Using an ab initio method, the potential energy has been calculated for the 29 lowest molecular states of symmetries ²Σ⁺, ²Π, ²Δ for the molecular ion RbH⁺. The calculation is based on nonempirical pseudopotentials and parameterized ?‐dependent polarization potentials. Gaussian basis sets have been used for both atoms. The spectroscopic constants for 18 electronic sates have been calculated by fitting the calculated energy values to a polynomial in terms of the internuclear distance R. Through the canonical functions approach the eigenvalue E_v, the abscissas of the corresponding turning points (R_min and R_max) and the rotational constants B_v have been calculated up to 24 vibrational levels for the considered bound states. The comparison of the present results with those available in literature shows a very good agreement. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Analytical energy gradient evaluation in relativistic and nonrelativistic density functional calculations

The expressions of analytical energy gradients in density functional theory and their implementation in programs are reported. The evaluation of analytical energy gradients can be carried out in the fully 4-component relativistic, approximate relativistic, and nonrelativistic density functional calculations under local density approximation or general gradient approximation with or without frozen core approximation using different basis sets in our programs. The translational invariance condition and the fact that the one-center terms do not contribute to the energy gradients are utilized to improve the calculation accuracy and to reduce the computational effort. The calculated results of energy gradients and optimized geometry as well as atomization energies of some molecules by the analytical gradient method are in very good agreement with results obtained by the numerical derivative method.     

Analysis of the effect of the electronic structure of the Cl atom in complexes of chlorides of group IV elements on Cl NQR frequency and asymmetry parameter

Analysis of changes in ³⁵Cl NQR frequency of complexes MCl₄.L and MCl₄.2L for M = Si, Ge, Sn and Ti was performed. The population of the atomic orbitals was calculated by the quantum chemistry methods PM3 and INDO. The results provided an explanation of the changes in ³⁵Cl NQR frequency and the asymmetry parameter upon complex formation. In the complexes of non-transition elements, a decrease in ³⁵C1 NQR frequency is first of all related to increasing population of p_z orbitals on Cl atoms. In the complexes of Ti, the increase in ³⁵Cl NQR frequency depends on a decrease in the p_π to d_π electron density transfer.     

Cyclohumulanoid Sesquiterpenes from the Culture Broth of the Basidiomycetous Fungus Daedaleopsis tricolor

A series of cyclohumulanoids, i.e., tricocerapicanols A–C (1a–1c), tricoprotoilludenes A (2a) and B (3), tricosterpurol (4), and tricoilludins A–C (5–7) were isolated along with known violascensol (2b) and omphadiol (8) from the culture broth of Daedaleopsis tricolor, an inedible but not toxic mushroom. The structures were fully elucidated on the basis of NMR spectroscopic analysis, and the suggested relative structures were confirmed via density functional theory (DFT)-based chemical shift calculations involving a DP4 probability analysis. In the present study, the ¹H chemical shifts were more informative than the ¹³C chemical shifts to distinguish the diastereomers at C-11. The absolute configurations of 1–5 were determined by comparing the experimental and calculated electronic circular dichroism (ECD) spectra. For 6 and 7, the same chirality was assigned according to their biosynthetic similarities with the other compounds. The successful assignment of some Cotton effects was achieved by utilizing DFT calculations using simple model compounds. The plausible biosynthesis of 1–7 was also discussed on the basis of the structural commonality and general cyclohumulanoid biosynthesis. Compounds 2a and 5 were found to simultaneously induce hyphal swelling and branching at 5.0 μg/mL against a test fungus Cochliobolus miyabeanus.     

Improved DFT calculation of Raman spectra of silicates

Very accurate vibrational spectra of silicates are obtained from DFT calculations if the appropriate Hamiltonian is used. Theoretical considerations suggest that the Hartree-Fock component of ACM1 hybrid functionals should be 1/6 instead of 1/4 for this class of compounds. When applied to the PBE functional this removes the scaling error of the calculated vibrational frequencies. Calculations using this PBE(n = 6) functional in combination with optimized Gaussian basis sets result in very small remaining deviations between observed and calculated Raman shifts, with standard uncertainties of ≈3.5 cm⁻¹, maximum deviations of ≈10 cm⁻¹, and no significant systematic trends. This has been confirmed for a wide range of silicate structures, for which high-quality Raman spectra have been published: forsterite α-Mg₂SiO₄ (nesosilicate), γ-Y₂Si₂O₇ (sorosilicate), K₂Ca₃Si₃O₁₀ (oligosilicate), K₂Ca₄Si₈O₂₁ (phyllosilicate), and α-quartz SiO₂ (tectosilictae).     

Analysis of the effect of the electronic structure of the Cl atom in complexes of chlorides of group IV elements on Cl NQR frequency and asymmetry parameter

Analysis of changes in ³⁵Cl NQR frequency of complexes MCl₄.L and MCl₄.2L for M = Si, Ge, Sn and Ti was performed. The population of the atomic orbitals was calculated by the quantum chemistry methods PM3 and INDO. The results provided an explanation of the changes in ³⁵Cl NQR frequency and the asymmetry parameter upon complex formation. In the complexes of non-transition elements, a decrease in ³⁵Cl NQR frequency is first of all related to increasing population of p_z orbitals on Cl atoms. In the complexes of Ti, the increase in ³⁵Cl NQR frequency depends on a decrease in the p_π to d_π electron density transfer.     

三磷酸铝的傅里叶变换红外光谱分析

提出了应用傅里叶变换红外光谱法,在由生产中产生的偏磷酸铝和磷酸二氢铝杂质存在下测定三磷酸铝(AlH2P3O10.2H2O)。从红外吸收光谱可见,三磷酸铝(Al-TP)及偏磷酸铝(Al-MP)分别在波数为986 cm-1及740 cm-1处存在特征吸收峰,而磷酸二氢铝在此波段无吸收峰。据此提出,用Al-MP作内标,以Al-TP与Al-MP的峰高比值与两者相应的浓度比值图,并采用曲线拟合或最低基线计算法制得工作曲线。由此可求得试样中Al-TP与Al-MP的含量比值。由于采用了Al-MP作内标,其干扰也得到消除。同时用标准(浙B/HG 204-88及GB/T 1714-1979)中所述方法对样品中磷酸二氢铝及水分的含量分别予以测定。按文中所给的公式,计算样品中三磷酸铝的含量。     

Structure and stability of thiourea with water, DFT and MP2 calculations

The relative stabilities of thiourea in water are investigated computationally by considering thiourea–water complexes containing up to 1–6 water molecules (CS(NH₂)₂(H₂O)_n=1–6) using density functional theory and MP2 ab initio molecular orbital theory. The results show that the thiourea complex is stable and has an unusually high affinity for incoming water molecules. The clusters are progressively stabilized by the addition of water molecules, as indicated by the increasing of the binding energy. The binding energy of the cluster to each H₂O molecule is about 33 kJ mol⁻¹ for n=1–5.The C–S bond, N–C bond distance, Mulliken populations and binding energy keep approximately constant as the clusters increase in size with an increasing number of H₂O molecules. As the solvation progresses, the C–S distance increases monotonically while the Mulliken populations on the C–S bond reduces monotonically with the addition of each H₂O molecule, indicating that the C–S bond of the thiourea unit in the clusters is de-stabilized with an increasing number of H₂O molecules. Charge transfers for the clusters are mainly found at N, S atoms of the thiourea.     

A general approach to calculating isotopic distributions for mass spectrometry

Fundamental principles for obtaining mass spectral isotopic distributions are applied to a general computer program that can be used to calculate and present in tabular and graphic form the isotopic contributions for any molecular formula. A unique feature is the retention of the isotopic distribution, exact mass, and absolute abundance for all individual peaks at each mass. Special considerations have been made for the large number of isotopic combinations that occur for many higher mass compounds. The computer program accepts the input of a molecular formula followed by interactive input of a number of parameters that affect the final presentation of the theoretical distribution profile.