龙爪芦荟和库拉索芦荟中微量锗的测定与红外光谱区别

采用吸光光度法对龙爪芦荟和库拉索芦荟中的微量锗进行了测定,并探讨了两种芦荟的红外光谱的区别。结果表明,龙爪芦荟中含锗量在26.1～28.6μg·g-1,回收率为91.6%～97 5%。库拉索芦荟中含锗量在16.8～20.0μg·g-1,回收率为87.1%～94.5%。两种芦荟的FT IR光谱图在2100cm-1处有明显差异,由此可区别两种芦荟。     

Synthesis of substituted 1-acyl-1′-biphenylylferrocenes. Crystal structures of 4-bromo-4′-ferrocenylbiphenyl and 1-(4′-cyanobiphenyl-4-yl)-1′-((<Emphasis Type="Italic">S</Emphasis>)-3-methylpentanoyl)ferrocene

Acylation of 4-bromo- and 4-cyano-4-ferrocenylbiphenyl with alkanoyl chlorides afforded the corresponding 1-acyl-1-biphenylylferrocenes in 20% yields. X-ray diffraction study of the above-mentioned bromo derivative and 1-(4-cyanobiphenyl-4-yl)-1-((S)-3-methylpentanoyl)ferrocene demonstrated that these ferrocenylbiphenyl derivatives crystallize in noncentrosymmetric space groups.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1864–1870, September, 2004.     

Mass spectrometry of π-complexes of transition metals : X. Methylferrocene

The study of deuterium labelled methylferrocenes has shown the ions C₁₁H₁₁Fe⁺, C₆H₆Fe⁺, C₅H₆Fe⁺ to originate from the isomerised form of the molecular ion in which all the hydrogen atoms are redistributed among the ligands.     

Structure,spectral properties and interconversions of bis-niobocenes and their dianions. The crystal and molecular structure of [(η5-C5H4SiMe2OSiMe2-η5 : η1-C5H3)2Nb2H2] [Na(OEt2)2]2

Electron-acceptor properties of bis-niobocenes (η⁵-C₅H₄Y)(H)$\text{Nb(η}{}^5\text{: η}{}^1\text{-C}{}_5\text{H}{}_3\text{X)}{}_2\text{N}$b(H)(η⁵-C₅H₄Y) with X  Y  H and XY  SiMe₂OSiMe₂have been investigated. Bis-niobocenes are shown to readily add two electrons forming stable salts of the corresponding dianions [(η⁵-C₅H₄Y)(H)Nb(η⁵ : η¹- C₅H₃X)₂Nb(H)(η⁵-C₅H₄Y)]^2-. The surplus electrons can be removed to give quantitative regeneration of initial neutral bis-niobocenes. The crystal and molecular structure of the title compound has been determined; R  0.044, interatomic distance are Nb…Nb 3.93, NbH 1.62, average NbC(π) 2.36, NbC(σ) 2.31 Å, other distances correspond to the usually observed values. Unlike the neutral bis-niobocenes, there is no direct metalmetal bond in the dianionic structures. This conclusion is supported by electronic spectra of neutral and dianionic species.     

Hydrolysis of tetrafluorosilane under neutral conditions: A quantum chemical study

A density functional quantum chemical study of the first step of SiF₄ hydrolysis under neutral conditions in the presence of one or two H₂O molecules was carried out. The reaction is endothermic and can follow three different pathways that involve the formation of penta-coordinated (pathway A) and hexacoordinated (pathways B and C) intermediates and transition states as the key steps. Pathway B is the most energetically favorable. All three pathways of the hydrolysis reaction lead to a product with formal retention of the configuration of substituents at the silicon atom. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 749–753, May, 2006.     

Syntheses and crystal structures of ferrocenyl derivatives of biphenyl

Arylation of ferrocene with substituted biphenyldiazonium tetrafluoroborates afforded 4-bromo-, 4-nitro-, and 4-cyano-4"-ferrocenylbiphenyls. 4-Nitro- and 4-cyano-4"-ferrocenylbiphenyls were studied by X-ray diffraction analysis. In the crystals of 4-nitro-4"-ferrocenylbiphenyl, the molecules are linked via stacking - interactions.     

微波促进的N-取代2,3,3a,4,7,7a-六氢异吲哚-1,3-二酮的Beller法合成

A rapid and facile synthesis of N-substituted 2,3,3a,4,7,7a-hexahydroisoindole-l,3-dione derivatives via microwave-promoted Beller three-component domino reaction of α,β,-unsaturated aldehydes, amides and N-substituted maleimides was described.     

On Mixed Pressure-Velocity Regularity Criteria to the Navier-stokes Equations in Lorentz Spaces,Part Ⅱ:The Non-slip Boundary Value Problem

This paper is a continuation of the authors recent work [Beir?o da Veiga, H.and Yang, J., On mixed pressure-velocity regularity criteria to the Navier-Stokes equations in Lorentz spaces, Chin. Ann. Math., 42(1), 2021, 1–16], in which mixed pressure-velocity criteria in Lorentz spaces for Leray-Hopf weak solutions of the three-dimensional NavierStokes equations, in the whole space R~3 and in the periodic torus T~3, are established. The purpose of the present work is to extend the result of mentio...     

[η<Superscript>5</Superscript>-C<Subscript>9</Subscript>H<Subscript>5</Subscript>(1,3-SiMe<Subscript>3</Subscript>)<Subscript>2</Subscript>]HfCl<Subscript>3</Subscript>: A monomeric 12-electron half-sandwich complex

The half-sandwich hafnium complex [gh⁵-C₉H₅(1,3-SiMe₃)₂]HfCl₃ (II) has been synthesized for the first time. The molecular structures of II and its synthetic precursor C₉H₅(1,1,3-SiMe₃)₃ (I) have been determined by X-ray crystallography. Compound II in the crystalline state, is a rare example of a monomeric 12-electron half-sandwich complex.     

A new proposal for the discretization of the Griffin—Wheeler—Hartree—Fock equations

A polynomial expansion is proposed as a new way to discretize the Griffin-Wheeler-Hartree-Fock equations of the Generator Coordinate Hartree-Fock method. The implementation of the polynomial expansion in the Generator Coordinate Hartree-Fock method discretizes the Griffin-Wheeler-Hartree-Fock equations through a numerical mesh which is not equally spaced. This procedure makes the optimization of Gaussian exponents in the Generator Coordinate Hartree-Fock method more flexible and more efficient. The results obtained with the polynomial expansion for atomic Hartree-Fock energies show this technique is very powerful when employed in the design of compact and high accurate Gaussian basis sets used in ab initio non-relativistic (Hartree-Fock) and relativistic (Dirac-Fock) calculations.