四元轻稀土硝酸盐水溶液体系{H2O+La(NO3)3+Pr(NO3)3+Nd(NO3)3}的热力学研究

在298.15 K条件下, 利用等压法研究了四元轻稀土硝酸盐水溶液{H2O La(NO3)3 Pr(NO3)3 Nd(NO3)3}及其3个二元亚系{H2O La(NO3)3}, {H2O Pr(NO3)3}和{H2O Nd(NO3)3}的热力学性质. 以NaCl或CaCl2水溶液为参考溶液, 测定了不同水活度条件下该四元溶液的渗透系数及各溶质组元的活度系数. 实验结果表明, 上述四元系与其3个二元亚系之间存在简单共性, 在实验误差允许范围之内(|Δ|≤0.0010), 该四元系符合偏理想溶液模型.     

Synthesis and Crystal Structure of Glycin·3,5-Dihydroxybenzoic Acid

The title compound glycin·3,5-dihydroxybenzoic acid (GDB) has been synthesized and characterized by single-crystal X-ray analysis. It crystallizes in orthorhombic, space group Pca21 with a = 25.513(10), b = 4.668(2), c = 9.150(4)(A), Z = 4, V = 1089.8(8)(A)3, C9H13NO7, Mr = 247.20, Dc = 1.507 g/m3, μ(MoKα) = 0.132 mm-1, F(000) = 520, R1 = 0.0322 and wR2 = 0.0611 for 885 observed reflections (I > 2σ(I)). The title compound is a 1:1 molecular complex of glycin and 3,5-dihydroxybenzoic acid, which is linked by O-H…O and N-H…O hydrogen bonds to form a three-dimensional framework. Test of SHG (second harmonic generation) indicates that NLO generation of the crystal is higher than that of KDP.     

Physically based molecular device model in a transient circuit simulator

Two efficient, physically based models for the real-time simulation of molecular device characteristics of single molecules are developed. These models assume that through-molecule tunnelling creates a steady-state Lorentzian distribution of excess electron density on the molecule and provides for smooth transitions for the electronic degrees of freedom between the tunnelling, molecular-excitation, and charge-hopping transport regimes. They are implemented in the fREEDA™ transient circuit simulator to allow for the full integration of nanoscopic molecular devices in standard packages that simulate entire devices including CMOS circuitry. Methods are presented to estimate the parameters used in the models via either direct experimental measurement or density-functional calculations. The models require 6–8 orders of magnitude less computer time than do full a priori simulations of the properties of molecular components. Consequently, molecular components can be efficiently implemented in circuit simulators. The molecular-component models are tested by comparison with experimental results reported for 1,4-benzenedithiol.     

手性氨基酚配体及其衍生物在不对称催化中的应用

综述了手性氨基酚配体及其衍生物的研究进展, 着重介绍其在不对称催化烷基化、烯基化、Michael加成、aldol反应及环丙化等反应中的应用.     

Dehalogenation of o-dihalogen substituted arenes and α,α′-dihalogen substituted o-xylenes with lanthanum metal

It was found that lanthanum metal caused the dehalogenation of o-dihalogen substituted arenes and α,α′-dihalogen substituted o-xylenes to generate the corresponding benzynes and o-quinodimethanes. When o-dihalogen substituted arenes were allowed to react with lanthanum metal in the presence of dienes, the Diels-Alder products between benzyne and dienes were formed in moderate to good yields. Similarly, the Diels-Alder adducts of o-quinodimethane with dienophiles were obtained, in the reaction of α,α′-dibromo-o-xylenes with lanthanum metal in the presence of dienophiles.     

Laser-enhanced ionization and laser-induced atomic fluorescence as element-specific detection methods for gas chromatography. Application to organotin analysis

The applicability of (1R,2R)-1,3-diacetoxy-1-(4-nitrophenyl)-2-propyl isothiocyanate [(R,R)-DANI] as a recently developed chiral derivatizing agent for the enantioseparation of a series of β-blockers is described. The thiourea diastereomers formed were analyzed by reversed-phase high-performance liquid chromatography, mixtures of water and methanol or acetonitrile being used for elution. Conditions of derivatizations (temperature, reagent excess and reaction time) were optimized, and the effects of organic modifiers on the retention and separation were investigated; the diastereomers could readily be baseline separated with methanol-containing mobile phases with resolutions between 1.58 and 2.72.     

An efficient procedure for the synthesis of coumarin derivatives using TiCl4 as catalyst under solvent-free conditions

The ability of titanium(IV) chloride as a catalyst to promote the Pechmann condensation reaction with a range of phenols and β-keto esters is described.The reaction was carried out by addition of TiCl₄ to a mixture of the phenol and the β-keto ester with thorough stirring in the absence of a solvent and represents an improvement on the classical Pechmann conditions. The yields of coumarins obtained via this novel protocol were significantly higher than those using the conventional method and the reaction duration was reduced to a few minutes or even a few seconds.     

Chemiluminescence in the reaction of the RuII trisbipyridyl complex with dimethyldioxirane

The reaction of dimethyldioxirane (1) with the Ru^II trisbipyridyl complex accompanied by chemiluminescence (CL) was studied. It is established that the intensity of CL and the rate of its decay increase proportionally with the concentration of Ru^II. The bimolecular rate constant (k ₂) of the reaction of1 with Ru^II was determined. The activation parameters (E _a and logA) for this reaction were calculated from the temperature dependence ofk ₂. The excitation yield of Ru^II* (η _Ru ^* ) was estimated. The quenching of Ru^II* by dioxirane was studied, and the bimolecular quenching constant and the coefficient of excitation regeneration were determined. It was suggested that the catalysis of the decomposition of1 and the excitation of Ru^II occurvia a mechanism of chemically initiated electron exchange. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1138–1142, June, 1997.     

Tetraazadibora[3, 3]paracyclophane

Starting from the para‐phenylenediamine derivative HN(SiMe₃)‐C₆H₄‐NH(SiMe₃), a lithiation and subsequent borylation give [(MeO)₂B]N(SiMe₃)‐C₆H₄‐N(SiMe₃)[B(OMe)₂] ( 1 ), the hydridation of which yields Li₂[(H₃B)N(SiMe₃)‐C₆H₄‐N(SiMe₃)(BH₃)] ( 2 ). Applying ZrCl₄ upon 2 initiates a condensation to give the title compound [‐N(SiMe₃)‐p‐C₆H₄‐N(SiMe₃)‐BH‐]₂, a hetero[3, 3]paracyclophane with two N‐B‐N chains that connect the para‐phenylene units. The product 3 crystallizes in the orthorhombic space group P2₁2₁2₁.     

Heterobimetallische Komplexe mit Chelatliganden aus mehrzähnigen Aminen und 1,1-Bis(diphenylphosphan)ethen

Heterobimetallic Complexes with Chelate Ligands from Multidentate Amines and 1,1-Bis(diphenylphosphine)ethene By an addition reaction of bidentate amines Me₂N(CH₂)_nNH₂ (n = 2, as-4C2N; 3, as-5C2N) and vinylidene derivatives with an activated double bond CH₂ = C(PPh₂)₂M(CO)₄ (M = Cr, Mo, W) were synthesized in dichlormethane unsymmetrical chelate ligands of the type as-4C2N (or as-5C2N)PPM(CO)₄. They gave with divalent salts M′Y₂ (Y = ac, M′ = Cu, Ni. Y = Cl, M′ = Zn, Cd, Hg) the coloured bimetallic complexes M′Y(as-4C2N) (or as-5C2N)PPM(CO)₄ which were characterized by means of IR-, UV/VIS spectroscopic and ¹H, ¹³C and ³¹P NMR measurements. The molecular structures of the complexes Cuac₂(as-5C2N)PPCr(CO)₄, I and that of CdCl₂(as-4C2N)PPCr(CO)₄, II , were acertained by results of single crystal X-ray determinations. In the crystals of I—II , the coordination polyhedron of each chromium(0) central atom containing two phosphorous donor atoms in a four-membered chelate ring and four terminal CO ligands is octahedrally distorted. This coordination sphere is connected at the carbon ring atom via a methylen chain group (spacer) with the bidentate amine ligand, which has a secondary and a tertiary nitrogen donor atom. Both nitrogen atoms are coordinated with the Cuac₂ under formation of a new kind of [4 + 2]-coordination in a trischelate complex. The six-membered diamine chelat ring in I has a chair-like conformation. The chromium-cadmium complex II is dimer from which the Cd central atoms obtain the rare coordination number of five. The related five-membered diamine chelate ring has δ conformation.