Near infrared study of aqueous lanthanide perchlorates

The near infrared spectra of water in aqueous solutions of La(ClO₄)₃, Pr(ClO₄)₃, Nd(ClO₄)₃, Gd(ClO₄)₃, Er(ClO₄)₃, Yb(ClO₄)₃, Lu(ClO₄)₃, and NaClO₄ have been measured in the concentration range from 0.3 to 2.5 mol-dm^–3, at 25°C. The relative contents of free OH groups in the 1.0, 1.6, and 2.2M solutions have been calculated from extinction coefficients for water at 1160 nm. They increase with increasing salt concentration and are greater in solutions of the lighter lanthanide perchlorates at any fixed molarity. The results are discussed in terms of the stoichiometry and structure of hydrated cations of trivalent lanthanides.     

Near infrared Raman spectra of human brain lipids

Human brain tissue, in particular white matter, contains high lipid content. These brain lipids can be divided into three principal classes: neutral lipids including the steroid cholesterol, phospholipids and sphingolipids. Major lipids in normal human brain tissue are phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidic acid, sphingomyelin, galactocerebrosides, gangliosides, sulfatides and cholesterol. Minor lipids are cholesterolester and triacylglycerides. During transformation from normal brain tissue to tumors, composition and concentration of lipids change in a specific way. Therefore, analysis of lipids might be used as a diagnostic parameter to distinguish normal tissue from tumors and to determine the tumor type and tumor grade. Raman spectroscopy has been suggested as an analytical tool to detect these changes even under intra-operative conditions. We recorded Raman spectra of the 12 major and minor brain lipids with 785 nm excitation in order to identify their spectral fingerprints for qualitative and quantitative analyses.     

水合乙酰丙酮镧系金属配合物的低频红外光谱及其结构

根据450～180cm~(-1)范围的红外光谱可容易地将二水(或三水)乙酰丙酮镧系金属配合物与单水配合物区分开来.这个范围内的有些谱带的频率随镧系金属原子序数的递增而稍有升高,说明这些谱带起源于M-O键的伸缩振动.用群论方法对不同构型的配合物计算了局部结构MO_8和MO_7应有的具红外活性的M-O伸缩振动形式数,并将其与三水(或二水)及单水配合物在此范围的谱带相比较.从而推断八配位的三水(或二水)配合物的配位多面体可能取正十二面体构型,而大多数七配位的单水配合物可能取单帽三棱柱构型。     

Theory of white lines in the x-ray absorption spectra of lanthanide complexes

Self-consistent multiple scattered wave formation was used to calculate the theoretical L-absorption edges of hydrated and unhydrated erbium trichloride in both bound state and continuum regions, in order to investigate the white line behavior. The white line was found to correspond to a transition to a d-like bound state lying just below the continuum threshold.     

A simple asymmetric lineshape for fitting infrared absorption spectra

Almost exclusively, lineshape functions used to model infrared (IR) absorption peaks are based on symmetric frequency distributions. However, in complex systems such as large biological macromolecules in aqueous solutions, the distribution of vibrational frequencies may in fact be asymmetric. In this communication, we show that asymmetry can be introduced to the standard symmetric Lorentzian and Gaussian lineshapes using a simple, easy to implement method. Our technique involves replacing the static width parameter of the symmetric profiles with a smoothly varying function that is wave number dependent. In this way, the width varies across the IR band resulting in an asymmetric peak. In our model, the width varies sigmoidally with wave number. As a demonstration, we fit experimental spectra of adenosine 5′-monophosphate (AMP).     

Effect of pyridine on infrared absorption spectra of copper phthalocyanine

Infrared absorption spectra of copper phthalocyanine in KBr pellet and pyridine solution in 400-1625 and 2900-3200 cm(-1)regions are reported. In the IR spectra of solid sample, presence of weak bands, which are forbidden according to the selection rules of D4h point group, is explained on the basis of distortion in the copper phthalocyanine molecule caused by the crystal packing effects. Observation of a new band at 1511 cm(-1) and change in intensity of some other bands in pyridine are interpreted on the basis of coordination of the solvent molecule with the central copper ion.     

Calculation of infrared absorption spectra using Gaussian variational wave packets

Formulas are developed for calculation of infrared absorption spectra with the help of Gaussian variational wave packets. The excitation is viewed as occurring to a linear combination of basis states corresponding to a Gaussian multiplied by Hermite polynomials of coordinates. Application of the formulas is examplified on HDO isolated in a D2O matrix. A simple approximation is proposed for the fundamental transitions.     

Far infrared and millimetre-wave absorption spectra of some low-loss polymers

Absorption spectra in the range 2–50 cm⁻¹ are reported for polyethylene, polypropylene and 'TPX' (basically poly 4-methyl pentene-1). The former has no resonances in this region and the continuum absorption can be represented by a simple quadratic function of wavenumber which, when extrapolated to radio frequencies, gives a good account of the observed losses. Polypropylene and 'TPX' show discrete absorption bands, but for these too there appears to be an underlying continuum. The millimetre-wave absorption possibly arises from a summation of the high frequency wings of the radio region relaxations and the low frequency wings of the far infrared resonances plus an inherent continuum which may be analogous to the broad absorption shown by non-polar liquids in the far infrared.     

Synthesis, infrared and fluorescence spectra of lanthanide complexes with a new amide-based 1,3,4-oxadiazole derivative

A new amide-based 1,3,4-oxadiazole derivative ligand 2,5-bis[2-(N,N-diethyl-1'-oxopropylamide)phenyl]-1,3,4-oxadiazole (L) and its complexes, Ln(NO3)3L (Ln=La, Eu, Gd, Tb, Er), were synthesized. The complexes were characterized by elemental analysis, infrared spectra and conductivity. The lanthanide ions were coordinated by O atoms from CO. The fluorescence properties of Eu(NO3)3L and Tb(NO3)3L in the solid state and in different solvents were investigated. Under the excitation of UV light, these complexes exhibit characteristic fluorescence of europium and terbium ions. The solvent factors influencing the fluorescent intensity were discussed.     

Structures,raman, infrared and electronic absorption spectra of pyridinium trihalides

Vibrational and electronic absorption spectra of PyHI₃, PyHIBr₂, PyHICl₂, PyHBr₃ and PyHBrCl₂ are presented and explained in terms of the vibrations and electronic transitions, respectively, of the pyridinium and trihalide ions. Two compounds, PyHI₃ and PyHBr₃, show charge transfer bands in the absorption spectra of the solids, and the vibrational spectrum of the PyH⁺ ion in solid PyHBr₃ differs from the normal PyH⁺ spectrum. PyHBr₃ as well as PyHI₃ contains asymmetric trihalide ions in the solid state, as can be concluded from the Raman and infrared spectra.     

Effect of structural characteristics of water on the infrared absorption and raman spectra

An analysis of band contour in the IR absorption (overtone region) and Raman spectra of water suggests that the high-frequency components of spectral bands correspond to a single continuous distribution in energy of H-bonds. A local increase in the probability density function at high frequencies, which leads to an increase in the population of states with weak hydrogen bonds, is caused by the specific behavior of the angular dependence of the energy of hydrogen bonds between water molecules. St. Petersburg State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 3, pp. 467–472, May–June, 1995. Translated by I. Izvekova     

A comparison of light scattering and far infrared absorption spectra of simple liquids

Light scattering and far infrared absorption spectra of CCl₄, C₂Cl₄, C₆H₁₂, CHCl₃, and CH₂Cl₂ in the liquid phase have been obtained in the range of 2 – 200 and 20 – 200 cm^?1 respectively. The energy absorption spectra obtained by the two techniques and the corresponding relaxation times were compared for each liquid. We observe systematic differences between the energy absorption profiles obtained from the light scattering spectra and the far infrared absorption spectras. We also find generally shorter relaxation times from the infrared absorption spectra. Despite the similarity of the physical processes leading to light scattering and to far infrared absorption some significant differences are observed (ref. 1,2).     

Fourier-transform infrared and optical absorption spectra of 4-tricyanovinyl-N,N-diethylaniline thin films

Thin films of 4-tricyanovinyl-N,N-diethylaniline (TCVA) were prepared for the first time using thermal evaporation technique. The molecular structure and electronic transitions of TCVA films were investigated by Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectra. The observed vibrational wavenumbers in FTIR spectra were analysed and assigned to different normal modes of the molecule. UV-vis electronic absorption spectral measurements of TCVA films were analysed to obtain the electronic transitions and optical band gap (E(g)). Other important optical parameters such as molar extinction coefficient (varepsilon(molar)), the oscillator strength (f), and the electric dipole strength (q(2)) were also reported.