An Introduction to the Solid State Polymerization of Transition-metal Complexes: A Comparative Study

Preliminary studies in this laboratory^' of topochemical and topotactic polyreactions of NiBr₂[P(CH₂CH₂CN)₃]₂ have shown that the reactions are in many cases characterized by a) product specificity, b) stereospecificity, c) “crystallographic specificity” and d) highly anisotropic “front motion” through individual single crystals. The polymerization reaction under investigation here is     

Calorific Effect of the Magnetically Induced Phase Transition in Induced Chiral Nematic Systems

The study of the calorific effect of the magnetically-induced phase transition in doped nematic phases is described. The systems examined consisted of PCB as a nematic host phase and S-N-1-phenylethyl-4n-alkylbenzamides as non-mesogenic optically active dopants. The calorific effect was estimated indirectly from the temperature dependence of the magnetic-field-threshold of the helical unwinding and of the reverse process; i.e. the helical winding. It appears that it is the ratio of the length of an optically active dopant and that of the nematic host which determines the temperature dependencies of such parameters as the helical pitch, microscopic twisting power, and latent heat. A comparison with the magnetocaloric effect in nematic liquid crystals¹ is also made.     

Laser Raman Investigation of Solid State Rearrangement of bis(O-lodobenzoyl) peroxide into 1-(2'-Iodobenzoyloxy)-1, 2-benziodoxolin-3-one

In solid state, the thermal rearrangement of bis(O-iodobenzoyl) peroxide which yields 1-(2'-iodobenzoyloxy)-1,2-benziodoxolin-3-one,is investigated by laser Raman spectroscopy. The intramolecular vibration spectra are used to characterize this chemical rearrangement. The phonon spectra obtained as a function of the rearrangement progress show that, in spite of the reported topotactic nature of the reaction, it proceeds by a heterogeneous mechanism. A temperature dependence study of the phonon spectra reveal no mode-softening for any optical phonons. Therefore, no evidence has been found for this reaction to be phonon-assisted.     

Concept of the Superpositional State in the Problem of Molecular Mesomorphism: An Analytical Review

It is shown that plastic and liquid crystals differ exclusively in characteristics of topologic order and are peculiar structural forms of more general superpositional state. On the basis of the generalization of the concept of a paracrystal a diagram of structural states is constructed allowing to classify partially ordered phases over the degree of destruction of long-range translational and orientational order.     

Investigation of the Solution Structures and Determination of the Growth Units of Cadmium Mercury Thiocyanate Crystal

To get a better understanding of the growth of cadmium mercury thiocyanate (CMTC), a promising nonlinear optical crystal, we have investigated the structures of its growth solutions by using Raman spectra. It has been found that Hg(II) ions coordinate with SCN^‐ through S atoms, forming the most stable complex of [Hg(SCN)₄]^2‐ in the solutions while Cd(II) ions bind to SCN^‐ around Hg(II) through the other end N atom. Thereby, taking [Hg(SCN)₄]^2‐ anions as centers, a network structure of Cd(II)‐N‐C‐S‐Hg(II) is formed in the solutions as in the crystal lattice. It is notably that there are other complexes, mostly the Cd(SCN)_n (n < 4) complexes, in the solutions. Therefore, the solution structure of CMTC is complicated, which is believed to contribute greatly to the difficulty of growing large single crystals. Based on the analysis of the solution structures, the reasonable growth units of CMTC are proposed.     

Conformation of Sterically Hindered 4-Methyl-2-oxo-2-trityl-1,3,2-dioxaphosphorinane in the Solid State and the Solution

Abstract  

The cis- and trans-2-methyl-2-oxo-2-trityl-1,3,2-dioxaphosphorinanes were obtained in the Arbuzov reaction of 2-methoxy-4-methyl-1,3,2-dioxaphosphorinane with trityl chloride. The NMR spectra (¹H, ¹³C and ³¹P) in solution indicated that trans isomer exists in the form of two noncongruent molecules and it adopts two different conformations: a halfchair and a sofa, while the cis isomer exists as the mixed half/chair–sofa conformer. The compounds crystallise as a pure chiral forms and as a racemates. The solid state structural studies show that NMR data are consistent with the single crystal X-ray analysis, but the conformation existing in the crystal structure is more complex than it can be supposed on sole NMR determination. Crystal data: cis-isomer chiral form: space group P3₂, a = 8.782, b = 8.782, c = 21.680, α = 90.00, β = 90.00, γ = 120.00, V = 1448.0; cis-isomer racemate: space group Pca2₁, a = 16.773, b = 8.491, c = 27.006, α = 90.00, β = 90.00, γ = 90.00, V = 3846.2; trans-isomer racemate: space group Cc, a = 16.133, b = 8.388, c = 16.158, α = 90.00, β = 117.20, γ = 90.00, V = 1944.8; trans-isomer chiral form: space group P 1, a = 8.397, b = 9.003, c = 14.944, α = 80.76, β = 74.38, γ = 63.31, V = 971.1).     

Investigation on the Aqueous Solution for Growth of Bimetallic Thiocyanate Complex Crystal Materials

The stability of cadmium mercury thiocyanate (CMTC) crystal growth solution was mainly discussed. The effects of temperature, pH value, time and KCl concentration on CMTC crystal growth were investigated. The effects of pH value and KCl concentration on crystallization habit of CMTC were also studied. The results show that when pH value ranges from 2.5 to 3.8, the solution is relatively stable, under the condition of pH ≤ 2.0 or pH ≥ 4.0, the solution has poor stability and some powder appears. The solution becomes unstable at high temperatures. When the concentration of KCl is more than 27% there has not generated CMTC crystal in the solution, a new kind of material produced from solution. The pH value and KCl concentration affect crystalline morphology of CMTC crystal.     

Texture transformations and orientational properties of lyotropic nematics in magnetic field

Dynamics of changes of the morphological properties and processes of orientation in lyotropic nematic mesophases by application of external magnetic field have been investigated in detail. The dynamics of changes of the optical birefringence values in nematic‐calamitic mesophase vs. time has been determined. The optical mappings of nonequilibrium magnetically induced textures, which have been observed for this mesophase during orientational process, and changes of birefringence vs. time are presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ru、Rh、Pd掺杂GaSb的电子结构和光学性质

运用第一性原理计算方法研究了过渡族金属TM(TM=Ru、Rh、Pd)掺杂GaSb的电子结构和光学性质,结果表明:TM掺杂GaSb主要以TM替代Ga(TM @Ga)缺陷存在,并可增强GaSb半导体材料对红外光区光子的响应,使体系光学吸收谱的吸收边红移;TM@Ga所引入的杂质能级分布于零点费米能级附近,这极大地增强了体系的介电性能,促进了电子-空穴对的产生和迁移,因而提升了掺杂体系的光电转换效率;Ru 掺杂对GaSb光学性质的改善最为明显,当掺杂浓度为6.25%(原子数分数)且均匀掺杂时,Ru掺杂GaSb体系对红外光区光子的吸收幅度最大,有效提升了GaSb光电转换效率和光催化活性。     

Co-Existent Biphasic Region of Nematic and Columnar Smectic Phases in Binary Mixture of Berberine and Alizarin Dye

We report the results of our studies on the optical and thermal properties of binary mixture of two compounds viz., berberine and alizarin dye. The mixture shows a very interesting co-existent biphasic region of nematic N + I and smectic C + I phases, sequentially when the specimen is cooled from its isotropic phase respectively at different concentrations of Alizarin dye in berberine molecule. The temperature variations of optical anisotropy, optical textures, and electrical conductivity have also been discussed. Aggregated molecular size has been confirmed by X-ray studies.     

Synthesis of Strontium Borophosphate,SrBPO5 by Solid State and Hydrothermal Methods and Characterisation

SrBPO₅ was synthesized by a solid‐state reaction reported and by a new solid state reaction using BPO4 as a phosphating agent. It was also obtained by a hydrothermal method. The structure of the compound was solved by Rietveld analysis before. The examination of X‐ray powder diffraction data showed that, SrBPO5 is isostructural with CaBPO₅ and BaBPO₅. It crystallizes in the trigonal system in P3₁21 and the refined unit cell parameters are a = 6.8488(1), c = 6.8159(2) Å, Z=3 and D_m 3.77 g/cm³.     

超硬B-C-N材料的电子结构、硬度和光学性质的第一性原理计算

本文基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法计算了z-BC₂N和z-B₂CN的4种晶体结构的电子结构、硬度和光学性质。结果表明,z-BC₂N(2)为直接带隙半导体,其禁带宽度2.449 eV,z-BC₂N(1)为间接宽带隙半导体,其禁带宽度为3.381 eV,而z-B₂CN(1)和z-B₂CN(2)为导体;硬度结果显示z-BC₂N(1)、z-BC₂N(2)和z-B₂CN(1)为超硬材料。最后通过计算z-BC₂N基本光学函数与光子能量的关系表征了其光学性质。分析结果表明,z-BC₂N结构可以用作良好的耐磨材料和窗口耐热材料。     

Determination of the Birefringence,the Twist Angle and the Thickness of the Nematic Liquid Crystal Sample by Renormalized Transmission Ellipsometry

Abstract

The birefringence, the twist angle and the thickness of the nematic liquid crystal sample were determined by means of the renormalized transmission ellipsometry. It was proposed that conventional sandwich-type cell is applicable to this ellipsometry measurement and the simplified numerical fitting procedure based on the 4 × 4 matrix method can provide the dispersion of the ordinary and the extraordinary refractive indices. The resolution of the twist angle and cell thickness measurement reaches to 0.05 deg. and 0.05 μm, respectively.     

Hydrogen Adsorption of Alkali Metal Complexes of Polycyclic Aromatic Hydrocarbon and Graphite,and Their Solid State Properties

The hydrogen adsorption in alkali metal complexes of graphite and triphenylene has been investigated by means of ESR and electrical resistivity under hydrogen atmosphere. In the first stage graphite compound C₈Rb, hydrogen molecules are dissociated into atoms which are stabilized in graphite gaps. C⁸K has a two stage hydrogen adsorption process: dissociation and charge transfer. For C₈Cs, the catalytic activity for hydrogen comes from the surface. The second stage compounds C₂₄M (M=K, Rb, and Cs) show weaker activities for hydrogen than the first stage ones. Triphenylene-potassium complex has a two stage process for hydrogen adsorption.     

Structural,electrical, thermal and optical properties of the nonlinear optical crystal L‐Arginine Fluoride

Single crystals of L‐Arginine Fluoride (LAF) have been grown by the slow evaporation technique, and the crystalline perfection was studied by HRXRD. Optical absorption studies reveal the lower cut off wavelength (280 nm) and the band gap (5.1 eV). The dielectric constant and dielectric loss have been measured as a function of frequency (42 Hz–5 MHz) and temperature (307‐368K) and the activation energy is 77 μeV. The thermal transport properties such as thermal conductivity (0.88 ± 0.02 W/mK) and specific heat capacity (482±24 J/kg/K) have been estimated by the photopyroelectric technique. The nonlinear refractive index n₂, is found to be of the order of 10⁻¹³ cm²/W by the Z‐scan technique.     

MeCeOx(Me=In,Zr)固溶催化剂制备及催化合成碳酸二甲酯研究

采用液相共沉淀法制备了MeCeOx(Me=In,Zr)双金属氧化物固溶催化剂.借助X射线衍射(XRD)、X射线光电子能谱(XPS)、程序升温还原(H2-TPR)、程序升温脱附(CO2-TPD、CH3OH-TPD)及漫反射傅里叶变换红外光谱(DRIFTS)等手段对催化剂物化性质进行了分析表征.在系统考察不同金属氧化物种类...     

Singlet Excitation Energy Migration in the Glassy and Single Crystalline States of 1,3-Diphenyl-5-(p-chlorophenyl)-2-pyrazoline

The crystal and molecular structure of the title compound were determined: a = 14.375(3), b = 11.534(3), c = 7.972(2) Å, α = 71.694(5), β = 79.125(5), γ - 74.861(5)°; space group PI. Refinement including all of the observed reflections (3145) leads to R = 0.086 (R_w= 0.074).

The molecular form in the crystalline state is fully extended in agreement with the suggestion by Birner et al. (Mol. Cryst. Liq. Cryst., 80, 11 (1982)), based on a NDDO-semiempirical calculation.

Whereas for the molecular form in the nematic liquid crystalline state a slightly parallel arrangement (～ 60°) of the dipole moment components perpendicular to the long axis is proposed, in the crystalline state these components are at an angle ～ 120° to each other, and somewhat antiparallel.

Preceding the melting point by approximately 10 degrees, DSC and thermal microscopy signals were observed; these depend eventually on solid-state polymorphism.     

Synthesis of four liquid crystals and study of alkyl chain effect on the nematic range for application in GC

Four liquid crystals (LCs) compounds which contain the 1,3,4-oxadiazole group were synthesized and characterized with spectroscopic techniques (IR, ¹H- and ¹³C NMR), their thermal properties were analyzed by the Differential Scanning Calorimetry (DSC) and the polarizing microscope (POM). A comparative study of the mesomorphic properties of these LCs and three other compounds which have already been used as a stationary phase in gas chromatography (GC) was carried out. These compounds have the same main nucleus. LCs V1, LC1, LC2 and LC3 gave a nematic (N) phase to the heating, LCs V2 and V3 recorded smectic A (SmA) and N phases. However, the range (N) has disappeared in V4.     

Measurement of the Refractive Index and Estimate of the Order Parameter in Oriented Liquid Crystals

The refractive indices of a cholesteric liquid crystal, cholesteryl dodecyl carbonate (CDC), and a smectic liquid crystal, p-n-octoxybenzilidene-p-n-butylaniline (OOBBA), have been measured as a function of temperature in the transition temperature regions. The measurements were made on oriented liquid crystals with an Abbe refractometer. By combining the data on ordinary and extraordinary refractive indices, the relative order parameter, α_aS/α, is plotted as a function of temperature. The behavior of the order parameter near the cholesteric to isotropic transition of CDC is similar to a nematic liquid crystal, whereas, the order parameter in OOBBA shows only a slight temperature variation like many solids.     

EDTA和KCl双掺杂下KDP溶液的稳定性研究

研究了EDTA与KCl不同掺杂浓度和不同过饱和比下KDP溶液的成核过程,测定了不同条件下KDP过饱和溶液的诱导期;根据经典成核理论计算了成核热、动力学参数,并分析了溶液稳定性随掺杂浓度的变化情况。利用化学腐蚀法对KDP晶体(100)面进行了腐蚀,得到了清晰的位错蚀坑,并使用光学显微镜观察了(100)面位错蚀坑的分布特点。结果表明,当过饱和度为4%、掺杂浓度为0.01 mol%EDTA和1 mol%KCl时,不仅KDP过饱和溶液的稳定性比较高,而且位错蚀坑的分布比较均匀、密度小,适合高质量的KDP晶体生长。