Theoretical studies on the butene double bond isomerization catalyzed by 5-H of 1-ethyl-3-methyl-imidazolium fluoride

The isomerization of 1-butene to trans-2-butene catalyzed by 5-H proton of 1-ethyl-3-methyl-imidazolium fluoride (EMImF) has been studied with density functional theory of quantum chemistry. The equilibrium states geometries and transition state geometry are optimized at the levels of B3LYP/6-31G(d,p) and B3LYP/6-311++G(d,p), respectively. The apparent activation barrier of isomerization is about 208 kJ/mol theoretically. It indicates that the 5-H proton on the imidazole ring of EMImF has certain catalytic activity to the butene double bond isomerization, which is similar to that of the 4-H proton. According to the data of intrinsic coordinate path, it can be determined that the isomerization is an elementary course and the hydrogen exchange of butene with EMImF is synergetic.     

AM1研究甲酰和苯甲酰叠氮的热分解反应

AM1 SCF calculations have been carried out to study thermolyses of formacyl and benzoyl azides. The results show that these thermolyses have several reaction routes yielding different products.     

Valence ab initio calculation of the potential-energy curves for the Ca<Subscript>2</Subscript> dimer

The electronic structure of the Ca₂ molecule has been investigated by use of a two-valence-electron semiempirical pseudopotential and applying the internally contracted multireference configuration interaction method with complete-active-space self-consistent-field reference wave functions. Core–valence correlation effects have been accounted for by adding a core-polarization potential to the Hamiltonian. The ground-state properties of the Ca₂ and Ca₂⁺ dimers have also been studied at the single-reference coupled-cluster level with single and double excitations including a perturbative treatment of triple excitations. Good agreement with experiment has been obtained for the ground-state potential curve and the only experimentally known A¹_u⁺ excited state of Ca₂. The spectroscopic parameters D_e and R_e deduced from the calculated potential curves for other states are also reported. In addition, spin–orbit coupling between the singlet and triplet molecular states correlating, respectively, with the (4p)¹P and (4p)³P Ca terms has been investigated using a semi-empirical two-electron spin–orbit pseudopotential. Acknowledgement.This work was supported by grant 5 P03B 082 21 from the Polish State Committee for Scientific Research (KBN).     

Thermodynamic properties of transition metals in aqueous solution: 1. The enthalpies of dilution of some aqueous transition metal chloride solutions at 25°C

Enthalpies of dilution H _D of aqueous solutions of the transition metal chlorides CdCl₂, CoCl₂, CuCl₂, MnCl₂, and NiCl₂ were measured from 1.0 molal to dilute solution at 25°C. The apparent molal enthalpy equations of Pitzer were then fit to the resulting H _D data and the parameters for these equations are presented. The heat of dilution data for CdCl₂ and CuCl₂ were in good agreement with results by other workers.     

Thermodynamic Aspects of the Increased Thermal Stability of Silicon by Doping with Transition or Rare-earth Metals

Summary. The main reason of the degradation of silicon monocrystals at heating is a structural transformation connected with a partial transition of the diamond-like structure into the structure of white tin. The reason for this transformation being observed under high pressures is the appearance of stress zones at the boundaries of variously oriented crystal microvolumes due to heat expansion anisotropy. The high stress concentration in the microvolumes provides sufficient pressure for the indicated phase transformation which results in the observed degradation of the electrophysical properties of silicon. The prevention of the structural transformation is considered to be possible by doping of Si by transition or rare-earth metals which increases the interatomic energy and decreases the thermal expansion coefficient. The choice of the doping additions is based on the bonding energy and the charge density calculated for a system of non-polarised ionic radii. The technology to increase the thermal stability of silicon has been patented^#. Patent of Russia, No 2094904, 13/10/1995     

Local many-electron states in transition metal oxides and their surface complexes with atomic and molecular oxygen

The local many-electron states in transition metal oxides (TMOs) are considered in the framework of the effective Hamiltonian of the crystal field (EHCF) method. The calculations are performed with use of the 5×5×5 clusters modeling TMOs with the rock salt crystal structure. The d-d excitation spectra are calculated and discussed with the aim of interpreting the experimental data on optical adsorption and electron energy loss spectra. The EHCF method is extended to account for the electron correlation in the d-shell and some electronic variables of ligands simultaneously. This approach is used to calculate the states of atomic and molecular oxygen on the surfaces of the TMOs. The possible role of geometric parameters of the adsorption complex is evaluated. The metal-oxygen distance and the exit of the metal ion from the surface plane are varied in a wide range. In the case of molecular oxygen different coordination forms are considered and for all adsorption systems the weights of different oxygen states (triplet, singlet, and charge transfer) are estimated.     

乙硼烷离子和自由基异构体重排与体系势能面的能量子化学计算研究

在B3LYP/6-311G(d,p)和QCISD(T)/6-311++G(3df,2p)(单点)水平下, 对B2H+5阳离子和B2H*5自由基全优化得到9个几何异构体: B2H+5单态体系(D3h, C1), B2H+5三重态(Cs, Cs, C1), B2H*5自由基(C2v, Cs, Cs, Cs). 得到势能面上与体系异构化过程相联系的5种过渡态.     

Magnetic nanocomposites based on cyclodextrin-containing molecular tubes and iron nanoparticles

Stabilization of metallic nanoparticles may be achieved by the formation of their adducts with polymers and/or nanotubes of various chemical composition. Here, water-soluble nanotubes based on β-cyclodextrin (β-tubes) were used for entrapping of Fe nanoparticles obtained by the reduction of iron-containing precursors ([Fe₃(CO)₁₁H][Et₄N] cluster and FeSO₄). Using methods of light-scattering, viscometry, and isothermal diffusion measurements, it was shown that the adducts are associated in aqueous solutions. The presence of iron nanoparticles and the shape and size of adducts were verified by transmission electron microscopy. The adducts are long (up to 600 nm and longer), translucent associates consisting of denser walls and transparent cores. The width of nanotubes is ∼150 nm and the thickness of the wall 3–25 nm. Their magnetic properties were demonstrated by electron paramagnetic resonance method. The mechanism of self-assembly of the adducts is discussed.     

Tetrazolecalix[4]arenes as new ligands for palladium(II)

The synthesis of new calix[4]arenes bearing two or four tetrazole liganting groups at the upper rim is decribed. The structures of tetrakis-tetrazolecalix[4]arene and its palladium dichloride (2:2) complex are examined by X-ray crystallography.     

新型层柱微孔材料─GaW_9Z_3（Z＝Co~（2＋），Fe~（3＋））柱撑Zn

新型层柱微孔材料─ＧａＷ_９Ｚ_３（Ｚ＝Ｃｏ~（２＋），Ｆｅ~（３＋））柱撑ＺｎＡｌ阴离子粘土的合成、表征及催化性能的研究张继余，余新武，张淑云，胡长文，梁兆君，王恩波（东北师范大学化学系，长春１３００２４）关键词阴离子粘土，杂多化合物，过渡金属，催化性...