Polarized infrared and Raman spectra of a CsHSO4 single crystal

The polarized absorption infrared (IR) and polarized Raman spectra of a CsHSO₄ single crystal at room temperature are presented and discussed in relation to the X-ray crystal structure. Breakdown of the selection rules for the X-ray determined C_2h factor group is observed. The vibrational factor group appears to be C₂. This implies C₁ site symmetry for the SO²⁻₄ ions. The polarization features of the HSO⁻₄ ion vibrations are predicted assuming that the longest S---OH bond vibrates independently of the SO₃ group vibrations. The ABC structure of the IR and Raman band arising from the νOH stretching vibration is explained on the basis of Fermi resonance.     

Polarized infrared and Raman spectra of CsHSeO4 and CsDSeO4 single crystals

The polarized absorption infrared spectra of CsHSeO₄ and CsDSeO₄ single crystals and polarized Raman spectra of the CsHSeO₄ single crystal were measured at room temperature. The polarization features of the internal vibrations of the HSeO⁻₄ ions are predicted on the basis of the X-ray structure assuming strong couping between the vibrations of the two shortest Se---O bonds and an intermediate Se---O bond. The bending methods γOH and δOH of a hydrogen bond appear at 805 cm⁻ and 1258 cm⁻¹, respectively. The νOH absorption has the ABC structure due to Fermi resonance of νOH with the overtones of the δOH and γOH vibrations. A similar shape of the νOH band is observed in the Raman spectra. The νOD absorption has a different shape from that of νOH. Intra-chain coupling was observed for the νOH and νOD vibrations.     

Vibrational spectra, assignments and normal coordinate calculation of acrylamide

The infrared spectra, low temperature infrared spectra, polarized infrared spectra and Raman spectra of acrylamide have been recorded and observed frequencies were assigned to various modes of vibrations on the basis of normal coordinate analysis, assuming C(s) point group symmetry. The potential energy distribution associated with normal modes is also reported. The assignment of fundamental vibrations agrees well with the calculated frequencies.     

High-resolution Raman spectroscopy study of phonon modes in LiBH4 and LiBD4

We have performed micro Raman measurements on LiBH4 and LiBD4 powders for temperatures between 5 and 300 K. At the lowest temperature, the peak energies agree very well with the results of a calculation within the density functional theory for the orthorhombic structure. The spectra are dominated by three separated bands: the external modes, the internal bending, and the internal stretching vibrations. Internal refers to vibrations within the BH 4 tetrahedrons, whereas external modes imply motions of Li and BH 4. The temperature dependence of the observed phonons corroborates the strong anharmonicity of the system. Due to the anharmonicity, Fermi resonances occur between the first order stretching modes and the second order bending modes of LiBH4. Moreover, the linewidths of the observed modes in LiBH4 have an Arrhenius-like component, with activation energies ranging from 250 to 500 K.     

IR, 1H NMR, mass, XRD and TGA/DTA investigations on the ciprofloxacin/iodine charge-transfer complex

Raman and infrared spectra of two polymorphous minerals with the chemical formula Fe3+(SO4)(OH)·2H2O, monoclinic butlerite and orthorhombic parabutlerite, are studied and the spectra assigned. Observed bands are attributed to the (SO4)2- stretching and bending vibrations, hydrogen bonded water molecules, stretching and bending vibrations of hydroxyl ions, water librational modes, Fe-O and Fe-OH stretching vibrations, Fe-OH bending vibrations and lattice vibrations. The O-H?O hydrogen bond lengths in the structures of both minerals are calculated from the wavenumbers of the stretching vibrations. One symmetrically distinct (SO4)2- unit in the structure of butlerite and two symmetrically distinct (SO4)2- units in the structure of parabutlerite are inferred from the Raman and infrared spectra. This conclusion agrees with the published crystal structures of both mineral phases.     

The Raman spectrum of hexamethylbenzene single crystal

A set of polarized Raman spectra obtained from suitable hexamethylbenzene single crystals at room temperature is presented. All the observed frequencies are attributed to intramolecular vibrations or lattice modes on the basis of clear polarization data.     

Vibrational spectroscopic study on polymorphism and molecular aggregation states in polyoxymethylene

Polarized Raman spectra of the moth-shaped single-crystal of orthorhombic polyoxymethylene (metastable phase) have been investigated by means of the Raman microprobe technique in the frequency range covering both molecular and lattice vibrations. The observed polarizations of the Raman bands are found to be strongly influenced by the optical alignment in the microscope, mainly by the polarization scrambling effect. By taking the optical effect into account, the orientation of the crystal axes in the single-crystal is investigated. Normal mode analysis of the orthorhombic crystal is performed based on the newly obtained polarization data. Raman spectra of two crystalline samples of trigonal polyoxymethylene (stable phase) differing in their morphology and in their structural orderliness are compared. In the spectrum of the needle-like crystal consisting of the fully extended molecules, measured at low temperature, eight Raman bands due to the E₂ symmetry species are newly detected     

Electrical anharmonicity and vibronic couplings contributions to optical nonlinearity of N-benzyl-2-methyl-4-nitroaniline crystal studied by FT-IR, polarized FT-NIR, resonance Raman and UV-vis spectroscopy

FT-IR and Raman spectra of the orthorhombic and monoclinic N-benzyl-2-methyl-4-nitroaniline (BNA) single crystals, powders, and BNA solutions were measured in the 15-4000 cm(-1) range, and complete assignments of bands to normal vibrations are proposed. The assignments have been reinforced by density functional theory (DFT) calculations. Polarized FT-NIR spectra of the orthorhombic (010) BNA plate were measured for the overtones and combinations analysis and for the mechanical and electrical anharmonicity estimation. Resonance Raman spectra of the orthorhombic BNA polymorph together with the resonance excitation profiles of fundamental and lattice vibrations, compared with the band maxima in the measured UV-vis-NIR spectra of BNA, have revealed vibronic couplings with intramolecular and intermolecular charge transfers. The role of anharmonicity, vibronic couplings and intermolecular hydrogen bonds as well as of the N-benzyl substituent are discussed and the origin of second harmonic generation in the orthorhombic BNA crystal is proposed.     

Vibrational properties of the nonlinear optical crystal β-BaTeMo2O9

We report growth of large single crystals of β-BaTeMo₂O₉, and single crystal infrared (IR) reflectance spectra as well as polarized Raman spectra for these crystals. Based on these results, the symmetry and LO–TO splitting have been established for the observed modes. We also propose assignment of the observed modes to the respective vibrations of structural units.     

Vibrational study of (NH4)2HPO4 and (ND4)2DPO4 single crystals. The PO4 ion vibration couplings

The PO₄ internal vibrations have been studied by measuring the polarized infrared (IR) spectra at room temperature (RT) and at low temperature (LT=20K) as well as the polarized Raman (R) spectra. The i.r. dichroism in the (010) plane is investigated in a great range of angles α (0°<α<135°) of the electric vector E with respect to the crystallographic axic c. Some intra ion couplings are inferred. No factor group splitting is observed in the RT IR spectra. However, simultaneously regarding the LT IR spectra and the R spectra promotes an interchain coupling inside the primitive cell. Strong resonance coupling effects are found for the PO₄ stretching modes with the in-plane mode δOH(δOD).     

Assignment of the in-plane molecular vibrations of the electron-donor molecule BDT-TTP based on polarized Raman and infrared spectra,in which BDT-TTP is 2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene

Infrared and Raman spectra of 2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene (BDT-TTP) and 1,3,4,6-tetrathiapentalene-2,5-dione (TTP-DO) are reported. The vibrational modes of TTP-DO are assigned with the aid of the depolarization ratio of solution Raman spectra, polarized reflection spectra and polarized Raman spectra. A D2h symmetry is assumed for the BDT-TTP molecule and its in-plane fundamental vibrations are assigned with the aid of the polarization ratio and the correlation with TTP-DO, tetrathiafulvalene (TTF), tetramethyltetrathiafulvalene (TMTTF) and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF). Normal coordinate calculation with a modified internal valence force field was carried out for the in-plane fundamental vibrations of TTP-DO and BDT-TTP. Ab initio calculations of the normal modes of BDT-TTP0 and BDT-TTP+ are compared with the empirical analysis.     

Electronic structures of organometallic complexes of f elements. Part 54. Electronic Raman and f-f transitions in the low temperature vibrational spectra of Cp3Ce(NCCH3)2

A comparison of the low temperature Raman spectra of Cp(3)Ce(NCCH(3))(2) (1), Cp(3)La(NCCH(3))(2) (2), Cp(3)La(NCCH(3))(2):Pr(3+) (3), Cp(3)La x NCCH(3) (4), Cp(3)Ce x NCCH(3) (5) and Cp(3)Tb x NCCH(3) (6) shows that the former compound exhibits three additional bands at 320, 2129 and 2154 cm(-1), which we ascribe to electronic Raman transitions. The two latter signals also appear in the low temperature IR spectrum of complex 1, but not in those of compounds 2-6. By performing crystal field (CF) calculations, the terminal states of the observed electronic Raman transitions could be identified. On the basis of both experimental and calculated CF energies as well as calculated wave functions the observed temperature dependence of mu(2)(eff) of complex 1 could be simulated in a satisfactory manner. A comparison of the low temperature Raman spectrum of compound 1 with the low temperature FIR spectrum of complex 2 shows that the selection rules for trigonal-bipyramidal coordination do not hold strictly for the skeletal vibrations. If the additional criterion of allowed vibronic side bands is applied to the transitions Gamma(1)-->Gamma(1, 4, 5, 6) of compound 3, the observed vibrational energies may be partly classified according to their symmetry.     

Electronic, infrared, and Raman spectral studies of the reaction of iodine with 4-aminopyridine

The reaction of iodine as an electron acceptor with the base 4-aminopyridine (4APY) has been investigated spectrophotometrically in chloroform at room temperature. The electronic absorptions, infrared and Raman spectra, photometric titration as well as elemental analysis of the obtained iodine complex indicate the formation of the pentaiodide charge-transfer complex with the general formula [(4APY)(2)](+)I(5)(-). The characteristic strong absorptions of I(5)(-) are observed around 380 and 295 nm. Far infrared and Raman spectra of the solid complex show the vibrations of the linear I(5)(-) ion with D(infinityh) symmetry at 154, 104 and 89 cm(-1) assigned to nu(s)(I--I), outer bonds, nu(s)(I--I), inner bonds and nu(as)(I--I) inner bonds, respectively.     

Polarized vibrational spectra of betaine monohydrate single crystal

The polarized infrared and Raman spectra of betaine monohydrate single crystal were measured and discussed in relation to the crystal structure. An assignment of the observed bands to the internal vibrations of the betaine and water molecules is proposed.     

Intermolecular interactions and geometry of non-rigid molecules in weak crystalline complexes: Vibrational spectra of 4,4′-dinitrobiphenyl complexes with biphenyl,biphenyl derivatives and p-terphenyl

Raman spectroscopy is used to study the complexes of 4,4′-dinitrobiphenyl with biphenyl, 4-hydroxybiphenyl, 4-bromobiphenyl and p-terphenyl, which crystallize in a highly unusual geometry. Their phonon spectra at 125 K and 18 K are compared and the effect of isotopic substitution of biphenyl on the phonon spectra of its complex is examined. Internal vibrations of the components in the crystalline complex are compared with those observed in the pure crystals of the components. The results from both phonon and intramolecular vibration studies show that these complexes form in fixed stoichiometries, are governed by geometrical factors, and are stabilized primarily by van der Waals interaction, although other kinds of interactions may provide additional stabilization. The 4,4′-dinitrobiphenyl molecule as well as biphenyl and p-terphenyl are centrosymmetric and remain so when the complexes are cooled from room temperature to 18 K. For biphenyl complex, this conclusion is supported by the observed IR spectra which show mutual exclusion between IR-active and Raman active vibrations. Crystal splitting is observed on the 410 cm^?1 vibration of 4,4′-dinitrobiphenyl. This splitting is attributed to the presence of more than one 4,4′-dinitrobiphenyl molecules in the complex unit.     

Structure and vibrational spectra of the bis(betaine)-selenic acid molecular crystal

The crystal structure of bis(betaine)-selenic acid has been determined by X-ray diffraction as orthorhombic, space group Pbca, with a = 11.591(2), b = 22.930(5), c = 12.045(2) Å and Z = 8. The crystal comprises hydrogen selenate ions, HSeO⁻₄, and two distinct betaine molecules, which are held together into a complex by short hydrogen bonds. One of the betaine molecules is present as the zwitterion form (CH₃)₃N⁺---CH₂---COO⁻ and the second occurs as the protonated form (CH₃)₃N⁺---CH₂---COOH. Powder FTIR and Raman spectra were measured. An assignment of the observed bands to vibrations of the hydrogen bonds and internal vibrations of the hydrogen selenate ion and the betaine molecules is proposed.     

电荷转移络合物对β-胡萝卜素共振拉曼散射截面的影响

利用Vaspec-2048-2紫外光谱仪和Renishaw InVia型共聚焦拉曼光谱仪,测量了极性溶剂1,2-二氯乙烷碘溶液中的β-胡萝卜素的紫外-可见吸收光谱和拉曼光谱.结果表明,生成络合物的β-胡萝卜素在460 nm处的紫外-可见吸收峰消失,并在1000 nm处出现β-胡萝卜素与碘形成络合物的吸收峰,致使514.5 nm激光激发时观察不到络合物中C-C(C—C,C=C)键的共振拉曼光谱.而溶液中没有形成络合物的β-胡萝卜素的C-C键拉曼散射截面减小.其机理为:β-胡萝卜素和碘溶液不稳定,β-胡萝卜素分子结构有序性减弱,导致相干弱阻尼C-C键振动减弱,使得其拉曼散射截面减小.     

Structure of Mg2.56V1.12W0.88O8 and vibrational raman spectra of Mg2.5VWO8 and Mg2.5VMoO8

Mg(2.56)V(1.12)W(0.88)O(8) crystals were grown from a MgO/V(2)O(5)/WO(3) melt. X-ray single-crystal diffraction studies revealed that it is orthorhombic with space group Pnma, a = 5.0658(5) A, b = 10.333(1) A, c = 17.421(2) A, Z = 6, and is isostructural with Mg(2.5)VMoO(8). Raman spectra are reported, and the assignment of the Raman bands is made by comparing the metal-oxygen vibrations of VO(4)/WO(4) tetrahedra in Mg(2.5)VWO(8) with the metal-oxygen vibrations of VO(4)/MoO(4) tetrahedra in Mg(2.5)VMoO(8). The stretching vibrations appearing at 1016 and 1035 cm(-)(1) are assigned to Mo=O and W=O double bonds, respectively, associated with the Mg(2+) cation vacancies.     

Polarized IR and Raman spectra and ab initio calculations for bis(guanidine) zirconium bis(nitrilotriacetate) hydrate single crystal [C(NH2)3]2[Zr[N(CH2COO)3]2](H2O)--the new laser Raman converter

Fourier transform polarized IR and Raman spectra of bis(guanidine) zirconium bis(nitrilotriacetate) hydrate single crystal [C(NH(2))(3)](2)[Zr[N(CH(2)COO)(3)](2)](H(2)O) have been measured in the regions 30-4000 and 80-4000 cm(-1) and correlated with X-ray structural data. The factor group analysis has been applied in the discussion of the dichroic dependence of the vibrational modes. The assignment of the internal vibrations for the [Zr(nitrilotriacetate)2]2- complex ion has been based on the ab initio quantum chemical calculations. The usefulness of the studied crystal as Raman laser converter was analyzed basing on the comparison of the spontaneous and stimulated Raman spectra.     

Experimental and DFT generated Raman study of two bent-core monomeric liquid crystalline compounds

The temperature dependence Raman spectra of two liquid crystalline compounds defined by the chemical formula of 3,5-difluoro-4?-(4-pentylcyclohexyl)-(1,1?-biphenyl)-4-carbonitrile and 3,4,5-trifluoro-4?-(4-pentylcyclohexyl)-1,1?-biphenyl is being first reported in this study. These compounds are bent-core monomers and their bent nature has been verified by the Density Functional Theory (DFT). The temperature-dependent Raman spectroscopy has been widely used in understanding the effects of temperature-based phase transitions on the molecular vibrations. The same spectroscopic technique; helps to understand various phase transitions temperature in the liquid crystalline compounds (LC) and also their molecular arrangements during the phase transitions. This study has successfully revealed the nature of intermolecular interactions between the investigated compounds during the phase transitions and the correlation between the observed Raman spectra and the measurement temperature. The contributions of different types of chemical bonds in the investigated LC compounds to their recorded Raman spectra have also been discussed in detail. In predicting the observed Raman spectra, the theoretical Raman spectra obtained from the DFT calculation was used as a reliable tool. In the light of the calculated data, the peak position, line width, and integral intensity data for each band in the observed Raman spectra were reported.