惰性元素化合物相对论效应的研究 I. 相对论效应的计算

分子形成中的相对论效应定义。用相对论电荷迭代EHT程序ITEREX计算了惰性元素氟化物XeF2, XeF4, XeF6, KrF2和RnF2的相对论效应, 分别为-72.91,是-160.34,-281.82, -25.44和-220.7kJ·mol^-^1。惰性元素化合物的相对论效应都是负值, 使分子趋于稳定。还计算了IF和CsF的相对论效应, 分别是10.68和17.42kJ·mol6-^1, 均为正值, 使分子能量升高, 证实了相对论效应在惰性元素化合物中的重要作用。     

Inclusion of relativistic effects into ZDO methods. I. A quasi-relativistic CNDO/1

A version of the CNDO /1 method has been outlined that includes dominant relativistic effects. The method utilizes a nonempirical parametrization based on atomic Dirac–Fock calculations. The goal of this QR -CNDO /1 method lies in its applicability to molecules consisting of arbitrary atoms (z = 1–118). Applications to molecular geometries and ionization potentials for 50 molecules are presented.     

Thermal dehydration and decomposition of M[M(C2O4)2]·xH2O (x=3 forM=Sr(II) andx=6 forM=Hg(II))

Strontium(II) bis (oxalato) strontium(II) trihydrate, Sr[Sr(C₂O₄)₂]·3H₂O and mercury(II) bis (oxalato) mercurate(II) hexahydrate, Hg[Hg(C₂O₄)₂]·6H₂O have been synthesized and characterized by elemental analysis, reflectance and IR spectral studies. Thermal decomposition studies (TG, DTG and DTA) in air showed SrCO₃ was formed at ca. 500°C through the formation of transient intermediate of a mixture of SrCO₃ and SrC₂O₄ around 455°C. Sharp phase transition from γ-SrCO₃ to β-SrCO₃ indicated by a distinct endothermic peak at 900°C in DTA. Mercury(II) bis (oxalato) mercurate(II) hexahydrate showed an inclined slope followed by surprisingly steep slope in TG at 178°C and finally 98.66% of weight loss at 300°C. The activation energies (E ^*) of the dehydration and decomposition steps have been calculated by Freeman and Carroll and Flynn and Wall's method and compared with the values found by DSC in nitrogen. A tentative reaction mechanism for the thermal decomposition of Sr[Sr(C₂O₄)₂]·3H₂O has been proposed.     

A study on mixed halide compounds MFX (M = Ca,Sr, Eu,Ba; X = Cl,Br, I)

MFX (M = Ca, Sr, Eu, Ba; X = Cl, Br, I) compounds have been prepared by solid-state reaction. Lattice parameters and X-ray diffraction patterns are presented for these compounds, which are all isostructural with tetragonal PbFCl. Attempts to synthesize solid solutions of Sr(Eu)FCl and of MFCl compounds with several rare earth oxychlorides are reported. The crystal chemistry of MFX, MHX, and LnOX compounds is briefly discussed in comparison, and the observed $\text{c}\text{a}$ ratios are interpreted on the basis of electrostatic calculations.     

Spin-frustrated trinuclear Cu(II) clusters with mixing of 2(S = 1/2) and S = 3/2 states by antisymmetric exchange. 1. Dzialoshinsky-Moriya exchange contribution to zero-field splitting of the S = 3/2 state

The mixing of the spin-frustrated 2(S = 1/2) and S = 3/2 states by the Dzialoshinsky-Moriya (DM) exchange is considered for the Cu 3(II) clusters with strong DM exchange coupling. In the antiferromagnetic Cu 3 clusters with strong DM interaction, the 2(S = 1/2)-S = 3/2 mixing by the in-plane DM exchange ( G x ) results in the large positive contribution 2 D DM > 0 to the axial zero-field splitting (ZFS) 2 D of the S = 3/2 state. The correlations between the ZFS 2 D DM of the excited S = 3/2 state, sign of G z and chirality of the ground-state were obtained. In the isosceles Cu 3 clusters, the in-plane DM exchange mixing results in the rhombic magnetic anisotropy of the S = 3/2 state. Large distortions result in an inequality of the pair DM parameters, that leads to an additional magnetic anisotropy of the S = 3/2 state. In the {Cu 3} nanomagnet, the in-plane DM exchange (Gx, Gy) mixing results in the 58% contribution 2 D DM to the observed ZFS 2 D of the S = 3/2 state. The DM exchange and distortions explain the experimental observation that the intensities of the electron paramagnetic resonance (EPR) transitions arising from the 2(S = 1/2) group of levels of the {Cu 3} nanomagnet are comparable to each other and are 1 order of magnitude weaker than that of the S = 3/2 state. In the ferromagnetic Cu 3 clusters, the in-plane DM exchange mixing of the excited 2(S = 1/2) and the ground S = 3/2 states results in the large negative DM exchange contribution 2 D DM' < 0 to the axial ZFS 2 D of the ground S = 3/2 state.     

ΔF = ±2 transitions in the hyperfine spectrum of Er I

The occurrence of 15ΔF=±2 transitions in the hyperfine spectrum of five lines of Er I was observed by means of high-resolution laser-atomic-beam spectroscopy. These normally forbidden transitions are caused by an external magnetic field which mixes closely lying hyperfine levels that have neighbouringF quantum numbers. If the Zeeman splittings under the applied magnetic field are small compared to the hyperfine splittings, the intensities of theΔF=±2 components are proportional to the square of the magnetic field strength. Under the variation of the laser intensity theΔF=±2 transitions show the same behaviour as homogeneously broadenedΔF=0, ±1 transitions. The relative intensities between theΔF=±2 components as well as the intensity ratios of theΔF=±2 to neighbouringΔF=±1 components are studied and interpreted in terms of first order perturbation theory.     

Photolumineszenz im System A2II B1/4II Gd1/2−x Eux □1/4 WO6 ≙ A8II BII Gd2−x Eux □ W4O24 (AII,BII = Sr,Ba)

Photoluminescence in the System A₂^II B_1/4^IIGd_1/2?xEu_x□_1/4WO₆ ? A₈^IIB^IIGd_2?xEu_xW₄O₂₄ (A^II, B^II = Sr, Ba) The emission and excitation spectra for the series Sr₈SrGd_2?xEu_x□W₄O₂₄ (HT- and LT-modifications) and Sr_9?yBa_yEu₂□W₄O₂₄ are reported and discussed. HT- and LT-Sr₈SrEu₂□W₄O₂₄ show an intense red emission, no concentration quenching is present.     

Dipolar recoupling of I = 1/2, S = 3/2 spin pairs with SEDOR for static and spinning samples

Spin-echo, double-resonance (SEDOR) dipolar recoupling experiments are illustrated on an I = 1/2, S = 3/2 spin system for static and spinning samples. An (15)N-(23)Na spin system is used to show that the simple pulse sequence is very effective in causing (15)N dipolar dephasing using either a (23)Na pi/2 recoupling pulse or a long radio-frequency (r.f.) recoupling pulse.     

不饱和类硅烯H2C=SiNaCl的密度泛函理论研究

采用密度泛函理论方法,在B3LYP/6-311G(d,p)水平上研究了不饱和类硅烯H2C=SiNaCl的结构.结果表明,不饱和类硅烯H2C=SiNaCl共有4种平衡构型,其中非平面的p-配合物型构型能量最低,是不饱和类硅烯H2C=SiNaCl存在的主要构型.对平衡构型间异构化反应的过渡态进行了计算,求得了转化势垒.计算预言了最稳定构型的振动频率和红外强度.     

不饱和类锗烯H2C=GeNaBr的密度泛函理论研究

应用密度泛函理论DFT方法,在B3LYP/6-311G(d,p)水平上研究了不饱和类锗烯H2C=GeNaBr的结构及异构化反应.结果表明,不饱和类锗烯H2C=GeNaBr有3种平衡构型,其中非平面的p-配合物型构型能量最低,是其存在的主要构型.并对平衡构型间异构化反应的过渡态进行了计算,求得了转化势垒,预言了最稳定构型的振动频率和红外强度.     

Adsorption of Cs(I), Sr(II) and Co(II) on Al2O3

The sorption of Cs(I), Sr(II) and Co(II) from aqueous solutions on alumina under various experimental conditions has been studied by batch techniques. Freundlich, Langmuir and Dubnin-Raduskevich equations have been used to interpret the sorption data. The values of various thermodynamic parameters have been determined. The sorption of Cs(I) and Sr(II) on alumina is exothermic in nature while that of Co(II) is an endothermic process. The H ^o values for Cs(I), Sr(II) and Co(II) were–23.29 KJ/mol at 298K,–35.3 KJ/mol at 293 K and 13.49 KJ/mol at 293 K, respectively. Negative values of G ^o show the spontaneity of the sorption processes; G ^o values of Cs(I) and Sr(II) becomes less negative at higher temperatures while the G ^o values of Co(II) become more negative with increasing temperature. At higher temperatures, less amounts of Cs(I) and Sr(II) and greater amounts of Co(II) are sorbed on alumina. The values of the mean free energies of sorption,E, for Sr(II) and Co(II) at various temperatures were within the range of 7–10 KJ/mol which show that these metals are sorbed on alumina predominantly by an ion-exchange process.     

A crossed molecular beam imaging study of the O(1D2)+HCl-->OH+Cl(2P J=3/2, 1/2) reaction.

A crossed molecular beam study is presented for the O((1)D(2))+HCl-->OH+Cl((2)P(J)) reaction at the collision energy of 6 kcal mol(-1). State-resolved doubly differential cross sections are obtained for the Cl((2)P(J=3/2) ) and Cl*((2)P(J=1/2) ) products by velocity-map ion imaging. Both products are slightly more forward scattered, which suggests a reaction mechanism without a long-lived intermediate in the ground electronic state. A small fraction (23 %) of the energy release into the translational degree of freedom indicates strong internal excitation of the counterpart OH radical. The contribution of the electronic excited states of O--HCl to the overall reaction is also examined from the doubly differential cross sections.     

反式共轭类碳烯CH2=CH-CH=C:LiF氢迁移反应的DFT研究

应用密度泛函理论DFT方法,在B3LYP/6-31G*水平上研究了反式共轭类碳烯CH2=CH-CH=C∶LiF的氢迁移反应.计算优化了反应过程中的所有反应物、中间体、过渡态和产物的几何构型,通过频率振动分析确定中间体和过渡态.结果表明,在β位上的H原子迁移过程中,经历一个带有三元环结构的中间体和两个带有三元环结构的过渡态.第一步反应势垒较大.     

Co-ordination Chemistry of ButCP,Mono-and Diphospha-allenes (R1P=C=CR2 and R1P=C=PR1) and 1,3-Diphosphacyclobutadiene

Abstract

A variety of novel coordination complexes derived from phospha-alkynes, and mono- and diphospha-allenes will be described.     

NMR study (1H, 13C, 31P) of the (C2H5)3-n. PXn compounds (X = Cl,Br, I; n = 0, 1, 2, 3)

The ¹H, ¹³C and ³¹P NMR data are reported for the (C₂H₅)_3-nPX_n compounds (X = Cl, Br, I; n = 0, 1, 2, 3). The chemical shifts are interpreted in terms of inductive and through-space effects of the X substituents together with a rehybridization of the phosphorous atom. The results of the coupling constants are in good agreement with the chemical shifts.     

Systems based on A2TeC6 (A = K, Rb, Cs, and Tl(I); C = Br and I) compounds with peritectic interactions

This work presents six peritectic quasi-binary systems based on A₂TeC₆ (A = K, Rb, Cs, and Tl(I); C = Br and I) ternary halides. We consider factors influencing physicochemical interactions between components in these systems. Original Russian Text ? E.Yu. Peresh, V.I. Sidei, O.V. Zubaka, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 2, pp. 360–363.     

Detection and characterization of intermolecular multiple-quantum coherence NMR signals of IS (I=1/2; S=3/2) spin systems

Intermolecular multiple-quantum coherences (iMQCs) have some intrinsic properties different from conventional single-quantum coherences in solution NMR. In this paper, we extended our study to heteronuclear iMQCs in IS (I=1/2, S=3/2) spin systems. A sample of sodium chloride (NaCl) water solution was taken as an example. Heteronuclear COSY revamped by asymmetric Z-gradient echo detection (CRAZED) experiments were performed. One- and two-dimensional heteronuclear iMQC spectra were obtained. The quantum-mechanical treatment was used to deduce the signal expressions. Magic angle experiments validate that the signals are indeed from intermolecular dipolar interaction and insensitive to the imperfection of radio-frequency (RF) flip angles. Both experimental results and theoretical analysis indicate that heteronuclear CRAZED experiment allows coherence transfer from spin-3/2 nuclei to spin-1/2, and vice verse. Furthermore, the dependences of iMQC signal intensities on RF pulse flip angles follow the same rules as those for heteronuclear IS (I=1/2, S=1/2 or 1) spin systems.