Low-frequency vibrations of molecular solids: XV. Globular molecule 1,2-dichloroethane

The far infrared and Raman spectra of polycrystalline 1,2-dichloroethane and 1,2-dichloroethane-d₄ for the low temperature modification have been measured from 450 to 33 cm⁻¹ at various temperatures from −100 to −182°C. Raman spectra of the high temperature crystalline modification for both samples were also investigated. The Raman data are in conflict with those previously reported. Assignments are made for the lattice vibrations in terms of the crystallographic unit cell C_2h⁵ (P_21/c) with two molecules per unit cell. The spectra of the high temperature modification are consistent with those expected for orientationally disordered crystals.     

High-pressure Raman spectra of l-histidine hydrochloride monohydrate crystal

Single-crystals of l-histidine hydrochloride monohydrate, C₆H₉N₃O₂·HCl·H₂O, were studied by Raman spectroscopy as a function of pressure in a diamond anvil cell up to 7.5 GPa at room temperature over the spectral range 3450-30 cm⁻¹. The effect of changing pressure on the vibrational spectrum is discussed. From the analysis of results we inferred that the crystal undergoes a reversible structural phase transition between 2.7 and 3.1 GPa. This transition is characterized by the splitting of a band related to torsion of CO₂⁻, the disappearance and appearance of modes related with stretching of OH⁻ and deformation of CO₂⁻, as well as with bands of low wavenumber which are assigned as lattice modes, and by the discontinuities of the curves of wavenumber versus pressure. Pressure coefficients for all modes observed in this work are also given.     

Vibrational spectra and IR dichroism of poly(tetramethyl-p-silphenylene-siloxane) and its chain structure

Raman spectra of poly(tetramethyl-p-silphenylene-siloxane) were investigated in solution with depolarization ratios and in the solid state. Polarized infrared (IR) spectra were studied on oriented polymer samples. Assignments of the vibrational bands are given and IR dichroic and Raman data are in agreement with tetragonal P4₁ space group symmetry. These data provide information on the arrangement of the Si? C₆H₄? Si groups in the unit cell. On the basis of vibrational spectra the dynamic interaction between adjacent benzene rings is negligibly small and the rings preserve their local D_2h Pseudosymmetry.     

The lattice vibrations of cubic A12MIVF6 compounds

The luminescence spectra of Cs₂MnF₆ and of Mn⁴⁺ in Cs₂GeF₆, Cs₂SiF₆ and Rb₂SiF₆ show bands due to low frequency vibrations which are not assignable using the unit cell model. Comparison of these spectra with infrared and Raman spectra and with a model for the lattice dynamics has suggested probable assignments for the vibrational and luminescence spectra.     

X-ray powder diffraction,FTIR, and raman study of strontium boroarsenate,SrBAsO<Subscript>5</Subscript>

In this study, SrBAsO₅ was synthesized by a solid state reaction using SrCO₃, As₂O₅, and H₃BO₃ as reported before. The x-ray powder diffraction, FTIR, and Raman data were in agreement with the reported crystal structure. It crystallizes in a hexagonal system in P3₁21, and the refined unit cell parameters are a = 7.056(3) Å, c = 6.898(1) Å, and Z = 3. It is isostructural with SrBPO₅. FTIR and Raman investigation of this compound were done for the first time in this study.     

The effect of high external pressures on the infrared and Raman spectra of crystalline tetra-n-propylammonium bromide

The infrared and Raman spectra of crystalline tetra-n-propylammonium bromide, (n-C₃H₇)₄NBr, have been measured in the 3000 – 700 cm⁻¹ region and vibrational assignments are proposed in part on the basis of the known crystal structure. Pressure-tuning infrared and Raman studies of this material were also undertaken using a diamond-anvil cell. There is a pressure-induced phase transition occurring between 1.8 and 2.1 GPa, which is most likely a second-order transition. Some differences are noted between the infrared data reported here and those given in an earlier high-pressure infrared study. The spectroscopic results will be useful in examining zeolites involving (n-C₃H₇)₄NBr as a template.     

Infrared and polarized raman spectra of kainite

The i.r. and Raman spectra of KMgClSO₄·3H₂O and its deuterated compound KMgClSO₄·3D₂O have been recorded and analysed. Due to site symmetry effects the i.r. inactive modes appear as sharp bands in the i.r. spectrum. Water bands indicate strong hydrogen bonding and show the presence of three crystallographically distinct water molecules in the unit cell.     

The effect of high external pressures on the infrared and Raman spectra of crystalline tetra-n-propylammonium bromide

The infrared and Raman spectra of crystalline tetra-n-propylammonium bromide, (n-C₃H₇)₄NBr, have been measured in the 3000 – 700 cm⁻¹ region and vibrational assignments are proposed in part on the basis of the known crystal structure. Pressure-tuning infrared and Raman studies of this material were also undertaken using a diamond-anvil cell. There is a pressure-induced phase transition occurring between 1.8 and 2.1 GPa, which is most likely a second-order transition. Some differences are noted between the infrared data reported here and those given in an earlier high-pressure infrared study. The spectroscopic results will be useful in examining zeolites involving (n-C₃H₇)₄NBr as a template.     

Syntheses and structural comparisons of two copper(II) complexes with the same formula having d-(+)- and d,l-1,2,2-trimethylcyclopentane-1,3-diamine ligands

Two five-coordinate copper(II) complexes, formulated as [Cu(L_a)₂Cl]BF₄ (1) and [Cu(L_b)₂Cl]BF₄ (2) having d-(+)-1,2,2-trimethylcyclopentane-1,3-diamine (L_a) and d,l-1,2,2-trimethylcyclopentane-1,3-diamine (L_b) ligands, have been synthesized and characterized. X-ray diffraction studies of 1 and 2 demonstrate that they crystallize in the different space groups (P2₁2₁2₁ for 1 and Pnma for 2), although they have identical unit cell volumes, due to the use of enantiomeric and racemic diamine ligands. One dimensional (1D) hydrogen-bond-sustained dimeric zigzag chains are formed by means of eight-membered N₂H₂CuBF₂ as well as 10-membered N₂H₄ClBF₂ hydrogen-bonded cycles. Thermal analyses for 1 and 2 are also described herein.     

Structures of Concentrated Sulfuric Acid Determined from Density, Conductivity, Viscosity, and Raman Spectroscopic Data

Addition of water to stoichiometric 100% sulfuric acid increases the density untila maximum results near 87 mole% H₂SO₄. The density and conductivity maximaand viscosity minimum, the latter two near 75 mole%, are direct macroscopicresponses to microscopic quantum mechanical properties of H₃O⁺ and of nearlysymmetric H-bond double-well potentials, as follows: (1) lack of H bonding tothe O atom of H₃O⁺; (2) short, 2.4–2.6 A, O—O distances of nearly symmetricH bonds; and, (3) increased mobility of protons in such short H bonds, give riseto the density maximum via (1) and (2); (1) produces the viscosity minimum;and the conductivity maximum results from (2) and (3). A pronounced minimumnear 1030 cm^–1 in the symmetric SO₃ stretching Raman frequency of HSO₄ ^–,observed near 45 mole% also results from double-well effects involving the shortH bonds of direct hydronium ion—bisulfate ion pair interactions. Estimates of theconcentrations of the (H₃O⁺)(HSO₄ ^–) and (H₂SO₄)(HSO₄ ^–) pair interactions weredetermined from Raman intensity data and are given for compositions between42–100 mole%     

Vibrational spectra of l-lysine monohydrochloride dihydrate and its two anhydrous forms

ATR FTIR and Raman spectra of l-Lys·HCl·2H₂O and two crystalline forms of anhydrous l-Lys·HCl are reported and discussed. Distinction with earlier published IR spectra of l-Lys·HCl·2H₂O registered by the KBr pellet method is explained by distortion of the spectra because of possible ionic exchange and partial decomposition.     

Vibrational analysis of l-alanine and deuterated analogs

Raman spectra of the polycrystalline l-alanine analogs CH₃CH(NH⁺₃)COO^?, CH₃CH(ND⁺₃)-COO^?, CD₃CD(NH⁺₃)COO^?, and CD₃CD(ND⁺₃)COO^? have been obtained. A normal coordinate analysis is carried out based on the experimental frequencies of the four isotopic analogs and a 34 parameter valence-type force field defined in terms of local symmetry coordinates. The final refinement, in which five stretching force constants are constrained to fixed values obtained from bond length data, results in an average error of 7 cm^?1 (0.9%) for the observed frequencies of the four isotopically substituted molecules. Band assignments are given in terms of the potential energy distribution for local symmetry coordinates. For non-deuterated l-alanine, the vibrations above 1420 cm^?1 and below 950 cm^?1 may be described as localized group vibrations. By contrast, the eight modes in the middle frequency range, viz. the three skeletal stretching, the COO^? symmetric stretching, one NH⁺₃ rocking, the symmetric CH₃ deformation, and the two methyne CH deformation vibrations, are very strongly coupled to one another. Some decoupling appears to take place in the perdeutero molecule, and all but five modes can be described as localized group vibrations.     

Vibrational properties of L-cysteine hydrochloride monohydrate crystal under high-pressure

L-cysteine hydrochloride monohydrate crystals, C₃H₇NO₂S·HCl·H₂O, were studied by Raman spectroscopy as a function of pressure in a diamond anvil cell up to 6.2 GPa in the spectral range 3500−30 cm⁻¹. From the analysis of the results, we inferred that the crystal is structurally stable in this pressure range. Some changes on the Raman spectra were observed for bands related to vibrational modes of the SH, NH₃⁺, CH₂, CCN, OH and COH units. These modifications were associated with conformational changes of the molecules in the unit cell undergone at high pressures. Comparing this behavior with those of L-cysteine, DL-cysteine and L-cysteine hydrochloride crystals in the same pressure range, we note greater stability for the hydrochloride monohydrate form. In the L-cysteine hydrochloride monohydrate crystal, the chloride ion and water molecule play an essential role in increasing the number of the hydrogen bonds, improving the structural stability of the crystal.     

Crystal and molecular structure of 3,5-dimethyl-1<Emphasis Type="Italic">H</Emphasis>-pyrazolide of 3-O-acetyl ursolic acid

3,5-Dimethyl-1H-pyrazolide of 3-O-acetyl ursolic acid (II) is obtained in the course of the interaction of 3 O-acetyl ursolic acid acyl chloride (I) and 3,5-dimethyl-1H-pyrazole. The crystal structure of compound II is determined from the single crystal XRD data (150 K, Bruker X8 Apex CCD autodiffractometer, MoK _α radiation). The crystals are rhombic, the unit cell parameters are as follows: a = 10.6034(2) Å, b = 12.4096(2)Å, c = 24.5972(5)Å, P2₁2₁2₁ space group. The structure consists of discrete acentric molecules. When pyrazolide II is boiled in the alcohol alkali solution, secondary hydroxyl is deacetylated and 3,5-dimethyl-1H-pyrazolide of ursolic acid IV is formed. Compounds II and IV are studied by NMR spectroscopy.     

Nanocrystalline nitrogenated diamond: An <Emphasis Type="Italic">N</Emphasis>-type electrode material

Nitrogenated nanocrystalline diamond thin films are grown from arc-plasma in CH₄/Ar/H₂/N₂-gas mixtures and characterized by AFM-and Raman spectroscopy, X-ray diffraction and resistivity measurements. It is shown by Mott-Schottky plots taken in indifferent electrolyte (0.5 M H₂SO₄) that the behavior of the nitrogenated nanocrystalline diamond thin-film electrodes resembles that of n-type semiconductor; the donor effective concentration therein is estimated.     

Vibrational spectra and structure of crystalline dipicolinic acid and calcium dipicolinate trihydrate

The i.r. (4000-30 cm⁻¹) and Raman (4000-20 cm⁻¹) spectra of 2,6-pyridinedicarboxylic acid C₅H₃N(COOH)₂, C₅H₃N(COOD)₂, 2,6-pyridine-4-d₁ dicarboxylic acid and calcium dipicolinate trihydrate (the equimolar salt of calcium and 2,6-pyridinedicarboxylic acid) at 100 K have been investigated.A tentative assignment is given by referring to the isotopic frequency shifts and group frequency considerations as well as to depolarization ratios. Thirty-four internal vibrations from the 39 expected modes have been observed for the crystalline dipicolinate ion, the relevant molecular point group being C _2ν. Cyclic centrosymmetric dimeric structures involving the carboxyl groups in the acid are proposed to explain the spectral features of this compound.     

Metatitanic acid: Synthesis and properties

Features of proton-for-lithium ion substitution in monoclinic and pseudocubic lithium titanate are studied by X-ray diffraction, NMR spectroscopy, and Raman spectroscopy. Proton incorporation into the lithium titanate structure decreases the parameter a _c of the pseudocubic unit cell from 8.28 Å in Li₂TiO₃ to =8.15 Å in H₂TiO₃. Metatitanic acid, like hydrous titania, has weak acid properties, but unlike titania, it sorbs hydrolyzable multicharged cations from aqueous solutions.     

<Emphasis Type="Italic">bis</Emphasis>(<Emphasis Type="Italic">N,N</Emphasis>-diethylnicotinamide) <Emphasis Type="Italic">p</Emphasis>-chlorobenzoate complexes of Ni(II), Zn(II) and Cd(II)

Three novel mixed ligand complexes of Ni(II), Zn(II) and Cd(II) with p-chlorobenzote and N,N-diethylnicotinamide were synthesised and characterized on the basis of elemental analysis, FTIR spectroscopic analysis, solid state UV-Vis spectrometric and magnetic susceptibility data. The thermal behavior of the complexes was studied by simultaneous TG-DTA methods in static air atmosphere and the mass spectra data were recorded. According to microanalytical results, formulas of complexes are C₃₄H₄₀N₄O₈ClNi, C₃₄H₄₀N₄O₈ClZn and C₃₄H₄₄N₄O₁₀ClCd. The complexes contain two moles of coordination waters, two moles p-chlorobenzoate and two mole N,N-diethylnicotinamide (dena) ligands per formula unit. In these complexes, the p-chlorobenzoate and N,N-diethylnicotinamide behave as monodentate ligand through acidic oxygen and nitrogen of pyridine ring. The decomposition pathways and the stability of the complexes are interpreted in the terms of the structural data. The final decomposition products were found to be as metal oxides.     

Über Cadmiumpermanganat-Hexahydrat

Zusammenfassung Das Pulverdiagramm, mit welchen die Gitterkonstanten und die Raumgruppe festgestellt wurden, sowie das IR-Spektrum und eineDTA-Untersuchung von Cd(MnO₄)₂·6 H₂O werden angegeben und kurz besprochen.X-Ray powder data, unit cell dimensions, space group, IR-spectrum andDTA data of Cd(MnO₄)₂·6 H₂O are given and shortly discussed.     

Structural roles of water in potassium nitrilosulphonate dihydrate,K3N(SO3)3.2H2O

The structural roles of the two types of lattice water in K₃N(SO₃)₃.2H₂O have been determined from the geometries of their immediate environments. Through hydrogen bonds of different lengths (and hence strengths), H₂O(1) links adjacent N(SO₃)₃^3?ions belonging to the same unit cell and lying on the same crystallographic mirror plane as O(1).H₂O(2) links identical N(SO₃)₃^3?ions contained in unit cells adjacent in the b direction, by very weak, equivalent hydrogen bonds. The hydrogen atoms of H₂O(1) are assigned to C_s sites in the unit cell and those of H₂O(2) are assigned to C₁ sites. The proposed site occupancies are verified by infrared spectroscopy using the “isotopic dilution” technique.