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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. 相似文献
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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。 相似文献
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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。 相似文献
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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。 相似文献
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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。 相似文献
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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 相似文献
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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。 相似文献
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Confluenines A–F, N-oxidized l-isoleucine derivatives from the edible mushroom Albatrellus confluens
Shuai-Bing Zhang Ying Huang He-Ping Chen Zheng-Hui Li Bin Wu Tao Feng Ji-Kai Liu 《Tetrahedron letters》2018,59(34):3262-3266
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. 相似文献
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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 Ev, the abscissas of the corresponding turning points (Rmin and Rmax) and the rotational constants Bv 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 相似文献
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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. 相似文献
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Ryuhi Kanehara Akio Tonouchi Katsuhiro Konno Masaru Hashimoto 《Molecules (Basel, Switzerland)》2021,26(14)
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. 相似文献
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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). 相似文献
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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 pz orbitals on Cl atoms. In the complexes of Ti, the increase in 35Cl NQR frequency depends on a decrease in the pπ to dπ electron density transfer. 相似文献
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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 pz orbitals on Cl atoms. In the complexes of Ti, the increase in 35Cl NQR frequency depends on a decrease in the pπ to dπ electron density transfer. 相似文献
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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。 相似文献
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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. 相似文献
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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. 相似文献