Infrared and Raman spectroscopic studies of glasses with NASICON-type chemistry

Structures of NASICON glasses of the general formula AB₂(PO₄)₃, where A = Li, Na or K and B = Fe, Ga, Ti, V or Nb, have been investigated using vibrational (IR and Raman) spectroscopies. Phosphate species appear to establish an equilibrium via a disproportionation reaction involving a dynamical bond-switching mechanism where both charge and bonds are conserved. B ions in the system acquire different coordinations to oxygens. Alkali ions cause absorptions due to cage vibrations. All the observed spectroscopic features are consistent with speciation involving disproportionation reactions.     

Infrared and Raman spectroscopic studies of l-valine l-valinium perchlorate monohydrate

FT-IR and FT-Raman spectra were recorded and analyzed for l-valine l-valinium perchlorate monohydrate crystals. The wave number assignments have been made for the functional groups, viz. COOH, COO(-), --[NH(3)](+), C--(CH(3))(2), C--C--N and C--H. One of the two amino acid residues remains in the zwitterionic form while the other residue exists in the cationic form. The symmetry of the ClO(4)(-) anion has been found to be lowered corresponding to ClO(2) group. The hydrogen bonds that prevail between amino acid residues, perchlorate anion and water molecule influence the wave numbers of several stretching and deformation modes to deviate from the expected values.     

Infrared and Raman spectroscopic studies of rotational isomers of O,O-diethyl phosphorodithioic acid

Infrared and Raman spectra of O, O-diethyl phosphorodithioic acid have been studied both at and below room temperature. The results show that the vibrations of P=S, P(-O)₂, P-S and S-H groups give multiple bands and the relative intensities of these bands vary as the temperature of the sample changes. According to the experimental results, we suggest that there are four rotational isomers of O, O-diethyl phosphorodithioic acid. Reasons for splitting the vibrational bands of these groups are also discussed.     

Infrared and Raman spectroscopic and theoretical studies of nonaaqua complexes of trivalent rare earth metal ions

Infrared (IR), far-infrared (far-IR) and Raman spectra have been recorded of the hydrated lanthanide(III) trifluoromethanesulfonates, [Ln(OH2)9](CF3SO3)3, (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), and also for the deuterated [La(OD2)9](CF3SO3)3 compound. This has enabled complete assignments of all seven metal-oxygen stretching modes for the first time. Force constant calculations have been performed for an LnO9(3+) moiety, with a tricapped trigonal prismatic oxygen atom arrangement in D3h point group symmetry. The lanthanide contraction in reflected in continuously increasing trends for the averaged LnO stretching frequencies and force constants with increasing inverse of ionic radii. The stretching force constants increased from 0.81 to 1.16 Ncm-1 for the LnO6 prism in the series from La to Lu, while those for the capping LnO3 bonds increased from 0.49 to 0.65 Ncm-1. The LnO stretching force constants showed a smooth correlation with the LnO bond distances to the prism oxygen atoms, while the correlation to the LnO capping oxygen atoms has a different shape, reflecting the increased ligand-ligand repulsion with decreasing lanthanide ion size.     

纳米尺寸氧化铝的红外光谱研究

用改进的溶胶-凝胶法制备了均一粒径的纳米尺寸Al~2O~3样品,在相同仪器条件下测得红外光谱。研究了烧结温度、反应物前驱体的pH值和分散介质对IR谱的影响。结果表明,纳米氧化铝IR谱的峰值、强度和带宽有规律变化与制备因素、颗粒尺寸及结构有关。当粒径变小处于表面的原子数增多时,与Al~2O~3纵向声子跃迁有关的谱带强度有增强趋势。     

Infrared spectroscopic studies of substituted 1,2-diphenylcyclopropenes

For the investigation of the character of a substituent at position 3 of the ring and the double bond, i.r. spectra of substituted 1,2-diphenilcyclopropenes were studied. Frequencies and integral intensities of the double bond stretching vibration band were determined. It was proved that changes of the band's parameters caused by intermolecular interactions are substantially smaller than effects observed by changing the substituent. On the basis of correlation between changes of intensities of the ν_CC band and resonance constants of substituents and the character of the frequency dependence, a conclusion was reached on the resonance interactions of the substituent with σ_Walsh —MO of the cycle.     

Infrared and Raman spectroscopic study of 1,2-benzenedithiol adsorbed on silver

Adsorption of 1,2-benzenedithiol (1,2-BDT) on a silver surface has been investigated by surface-enhanced Raman (SER) and reflection-absorption infrared (RAI) spectroscopy. The molecule was adsorbed on silver very favorably by forming two Ag---S bonds after deprotonation. From the RAI spectral pattern, the benzene ring of adsorbed 1,2-BDT was presumed to be tilted by ca. 38° from the surface normal. This RAI information was used to test the validity of various proposed SER selection rules. Being frequently quoted in the literature, the presence or absence of the benzene ring CH stretching vibration in the SER spectrum seemed, in fact, to be a very useful indicator in judging the perpendicular or parallel orientation of the benzene ring with respect to the surface. However, the so-called in-plane/out-of-plane dichotomy as well as the more elaborate symmetry-based electromagnetic selection rule was found not to work in the present system.     

Infrared and Raman spectroscopic investigations of δ2-oxazolin-5-ones

The infrared and Raman Spectra of saturated and unsaturated ²-oxazolin-5-ones (azlactones) have been studied for CCl₂, CHCl₃, i-PrOH, and t-BuOH solutions and for the solid phase. Frequency assignments have been made for C=O bond stretching in the region 1825–1770 cm^–1 and for a mixed C=C and C=N vibration at 1690–1550 cm^–1. All of the azlactones showed an intense, characteristic absorption in a narrow range near 900 cm^–1 which was assigned to a deformation vibration of the oxazolone ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1133–1136, August, 1989.     

Infrared and Raman matrix isolation studies of methylamine

Infrared (4000-50 cm^?1) and Raman spectra are reported of methylamine, methylamine-d₁ and methylamine-d₂ trapped in argon and nitrogen matrices at 4–20 K. An anomalous intensity variation was found for the NH₂ wagging mode of methylamine isolated in nitrogen matrices, while in argon matrices the NH₂ wagging absorption exhibited a complex structure due to matrix site effects. A normal coordinate analysis was carried out using a new assignment of the NHD twisting frequency. Barriers to internal rotation in argon and nitrogen matrices, calculated from the observed torsional frequencies, are compared with the gas phase value.     

Raman and FTIR spectroscopic studies of copolymers of methyl methacrylate with butadiene

The comprehensive characterization by Raman and IR spectroscopy of the products of the free-radically initiated copolymerization of methyl methacrylate with 1,3-butadiene is reported. Raman spectroscopy has been used to determine quantitatively the microstructure of the polymerized 1,3-butadiene units in the copolymers.     

Infrared spectroscopic studies of free-base tetraphenylporphine and its dication

We present here the infrared absorption spectra of free-base tetraphenylporphine and its dication. Most of the allowed IR bands of porphyrin skeletal are observed in pairs due to two-fold symmetry of the free-base tetraphenylporphine. Observation of some new bands, disappearance of few bands in the IR spectrum of dication are interpreted on the basis of point group symmetry S4. Intensity change in the observed bands due to vibrational motion of the phenyl rings for dication is also explained on the basis of symmetry of dication. Sharing of electrons of the B(1u) orbitals by the two added protons are responsible for the shifts in the position of certain IR bands for dication.     

Biogeological Raman spectroscopic studies of Antarctic lacustrine sediments

Analysis of lacustrine sediments is an accepted method for deciphering the palaeoenvironment of a lake's catchment area, as each strata of the sediment gives information about the rock type it was eroded from and also the state of the lake, i.e. oxic or anoxic. Antarctica has long been accepted as a putative analogue for Mars, so the analysis of Antarctic material may give results that can be compared to sediments on Mars. Raman spectroscopy has been selected as the method of analysis as it does not destroy the sample, can be used in situ and requires very little sample preparation. It is a suitable method for analysing both inorganic and organic matter and a miniature spectrometer is currently being developed for use in the field. The results from the spectrometers can serve as a guide for analysing sediments on Mars. It has been shown that Raman spectroscopy can detect and differentiate between oxic and anoxic sediments. Both 1064 and 785 nm wavelengths are suitable for laser excitation of organic and inorganic matter.     

Infrared, Raman, and DFT vibrational spectroscopic studies of C60F36 and C60F48

IR and Raman spectra of two fluorofullerenes, C60F48 and C60F36, are thoroughly studied. Assignment of the experimental spectra is provided on the basis of density functional theory (DFT) computations. Perfect correspondence between experimental and computed spectra enabled us to confirm that the major isomer of C60F48 has D3 symmetry. It was found that as-synthesized samples of C60F36 consist mainly of C3 and C1 isomers in ca. 2:1 ratio and 2-3% of T-symmetric structures. Extensive AM1 and DFT computations have shown that all three structures are the most stable isomers of C60F36. Previous structural assignment of the C3 isomer (Gakh, A. A.; Tuinman, A. A. Tetrahedron Lett. 2001, 42, 7137-7139) was confirmed by the vibrational data.     

Raman spectroscopic studies of terthiophenes for molecular electronics

The effect of thiol and selenol functionalization on the vibrational spectra and photochemical stability of terthiophene based molecular wires was investigated using surface-enhanced Raman scattering (SERS). The molecules were found to exhibit markedly different properties at the silver surface of the SERS substrate, despite having almost identical Raman spectra in solution and in the solid state. In contrast to terthiophene (3T), the bisthiolterthiophene (T3) and biselenol-terthiophene (Se3) molecules were stable against photoinduced structural changes when adsorbed to the metal surface at low concentrations. This indicates that the strong bonds to the silver surface, via S or Se terminal atoms, leads to a rapid decay of photoexcited states. Comparison with ab initio calculations shows that both T3 and Se3 bind with only one of the functional groups to the Ag surface.     

Infrared and Raman spectroscopic characterization of the hydrogen-bonding network in l-serine crystal

The IR spectra (4000–400 cm⁻¹) of neat and isotopically substituted (ND/OD ≤ 10% D and ≅30% D) polycrystalline l-serine (α-amino-β-hydroxypropionic acid; HO–CH₂–CH(NH₃)⁺–COO⁻) were recorded in the temperature range 300–10 K and assigned. The isotopic-doping/low-temperature methodology, which allows for decoupling of individual proton vibrational modes from the crystal bulk vibrations, was used for estimating the lengths and energies of the different H-bonds present in l-serine crystal. To this end, the frequency shifts observed in both the NH/OH stretching and out-of-plane bending spectral regions (relatively to reference values for these vibrations in non-hydrogen-bonded l-serine molecules) were used, together with previously developed empirical correlations between these spectral parameters and the H-bond properties. In addition, the room-temperature Raman spectrum (4000–150 cm⁻¹) of a single crystal of neat l-serine was also recorded and interpreted. A systematic comparison was made between the spectroscopic data obtained currently for l-serine and previously for dl-serine, revealing that the vibrational spectra of the two crystals reflect well the different characteristics of their hydrogen-bond networks, and also correlate accurately with the different susceptibility of the two crystals to pressure-induced strain.     

Raman spectroscopic studies on surface coordination mechanism of benzotriazole and triphenylphosphine with metals

The complexes of benzotriazole (BTAH) with Ag, Cu, Fe, Zn and Ni were prepared respectively in the non-aqueous solution by the direct electrochemical synthesis and characterized by microanalysis and normal Raman spectroscopy. The influence of the neutral ligand of triphenylphosphine (pph₃) on the coordination process was deduced by the normal Raman spectroscopy and electrochemistry. The metals were classified into two categories. For the first type, such as Cu and Ag, CuBTA and AgBTA were obtained in the solution without pph₃. The introduction of pph₃ led to its participation in the coordination processes of BTAH with Cu or Ag and appeared in the final complex. Fe, Zn and Ni belonged to the second type, there was no influence on the coordination of BTAH with Zn, Ni and Fe, i.e., the final complexes were Fe(BTA)₂, Zn(BTA)₂ and Ni(BTA)₂, respectively, in the solution with/without pph₃. The electrochemical results revealed that the BTAH can inhibit the corrosion of all the above metals, and the introduction of pph₃ resulted in the decrease of inhibition efficiency to Cu surface, while no influence was observed on the Ni surface. The different role of pph₃ was explained in terms of hard/soft acids and bases rule and coordination mechanism was proposed.     

Raman spectroscopic studies on surface coordination mechanism of benzotriazole and triphenylphosphine with metals

The complexes of benzotriazole (BTAH) with Ag, Cu, Fe, Zn and Ni were prepared respectively in the non-aqueous solution by the direct electrochemical synthesis and characterized by microanalysis and normal Raman spectroscopy. The influence of the neutral ligand of triphenylphosphine (pph₃) on the coordination process was deduced by the normal Raman spectroscopy and electrochemistry. The metals were classified into two categories. For the first type, such as Cu and Ag, CuBTA and AgBTA were obtained in the solution without pph₃. The introduction of pph₃ led to its participation in the coordination processes of BTAH with Cu or Ag and appeared in the final complex. Fe, Zn and Ni belonged to the second type, there was no influence on the coordination of BTAH with Zn, Ni and Fe, i.e., the final complexes were Fe(BTA)₂, Zn(BTA)₂ and Ni(BTA)₂, respectively, in the solution with/without pph₃. The electrochemical results revealed that the BTAH can inhibit the corrosion of all the above metals, and the introduction of pph₃ resulted in the decrease of inhibition efficiency to Cu surface, while no influence was observed on the Ni surface. The different role of pph₃ was explained in terms of hard/soft acids and bases rule and coordination mechanism was proposed.     

Raman spectroscopic and DSC studies of diglycine-perchlorate (DGPCl)

Single crystals of diglycine perchlorate (DGPCl) and deuterated diglycine perchlorate (DDGPCl) are synthesized and studied using differential scanning calorimetry (DSC) and Raman spectroscopy. DSC data indicated that both DGPCl and DDGPCl undergo a reversible first-order phase transition (solid-solid) at −11.5 °C and −9.3 °C, respectively. The Raman spectra of DGPCl and DDGPCl obtained at ambient temperature are analyzed to infer on the strength of hydrogen bonding in this compound relative to the parent compounds. The occurrence of NH stretching frequency at higher value in DGPCl in comparison with glycine suggests presence of a weak N–H?O hydrogen bond in DGPCl than in glycine. The lower isotropic melting temperature of DGPCl as compared to that of glycine is understood on the basis of the relative strength of hydrogen bonding in these compounds.     

Infrared spectroscopic studies of transition metal complexes and polarizability effect

The literature data on substituent influence on the CS, CN, NC, NN, and NO stretching frequencies (ν) in the IR spectra and in specific cases on their respective stretching force constants (k) have been analyzed for 28 series of the transition metal complexes. The ν and k values were first established to depend not only on the inductive and resonance effects but on the polarizability of substituents as well. The contribution of the polarizability effect varies from 0 to 57% with the type of series.     

Resonance Raman spectroscopic studies of hydroperoxo-myoglobin at cryogenic temperatures

In agreement with previous reports (Gasyna, Z. FEBS Lett. 1979, 106, 213-218 and Leibl, W.; Nitschke, W.; Huettermann, J. Biochim. Biophys. Acta 1986, 870, 20-30) radiolytically reduced samples of oxygenated myoglobin at cryogenic temperatures have been shown by optical absorption and EPR studies to produce directly the peroxo-bound myoglobin at 77 K. Annealing to temperatures near 185 K induces proton transfer, resulting in the formation of the hydroperoxo heme derivative. Resonance Raman studies of the annealed samples has permitted, for the first time, the direct observation of the key nu(Fe-O) stretching mode of the physiologically important Fe-OOH fragment of this ubiquitous intermediate. The assignment of this mode to a feature appearing at 617 cm(-1) is strongly supported by documentation of a 25 cm(-1) shift to lower energy upon substitution with (18)O(2) and by a 5 cm(-1) shift to lower energy for samples prepared in solutions of deuterated solvent.