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[Tetraamminecadmium(II)] bis(permanganate) (1) was prepared and its crystal structure was elucidated with XRD-Rietveld refinement and vibrational spectroscopic methods. Compound 1 has a cubic lattice consisting of a 3D hydrogen-bonded network built as four by four distorted tetrahedral blocks of [Cd(NH3)4]2+ cations and MnO4– anions, respectively. The other four permanganate ions are located in a crystallographically different environment, placed in the cavities formed by the attachment of the building blocks. A low-temperature (≈100 °C) solid phase quasi-intramolecular redox reaction producing ammonium nitrate and amorphous CdMn2O4 could be established. Neither solid phase nor aqueous solution phase thermal deammoniation of compound 1 can be used to prepare Cd(MnO4)2 and [Cd(NH3)2(MnO4)2]. During deammoniation of compound 1 in aqueous solution a precipitate consisting of Cd(OH)2 forms. Additionally, solid MnO2 and ammonium permanganate (NH4MnO4) forms. The solid phase deammoniation reaction (toluene used as heat convecting medium) with subsequent aqueous leaching of the ammonium nitrate formed has proved to be an easy and convenient technique for the synthesis of amorphous CdMn2O4+x type NOx and MeSH sensor precursors. The 1-D perdeuterated complex was also synthesized to distinguish the N–H(D) and O–H(D) fragment signals in the TG-MS spectra and to elucidate the vibrational characteristics of the overlapping Mn–O and Cd–N frequencies.

2þ cations. The other four MnO � 4 anions are located in a crystallographically different environment, namely in the cavities formed by the attachment of the building blocks. A low-temperature quasi-intramolecular redox reaction producing NH4NO3 and amorphous ZnMn2O4 could be established occurring even at 1008. Due to H-bonds between the (Zn(NH3)4)2þ cation and the MnOanion, a redox reaction took place between the NH3 and the anion; thus, thermal deammoniation of compound 1 cannot be used to prepare (Zn(NH3)2)(MnO4)2 (contrary to the behavior of the analogous perrhenate (ReO � 4 ) complex). In solution-phase deammoniation, a temperature-dependent hydrolysis process leading to the formation of Zn(OH)2 and NH4MnO4 was observed. Refluxing 1 in toluene offering the heat convecting medium, followed by the removal of NH4NO3 by washing with H2O, proved to be an easy and convenient technique for the synthesis of the amorphous ZnMn2O4.

The vibrational properties of two fluorophenol derivatives, 2-fluorophenol ( 1 ) and 2,3,5,6-tetrafluorohydroquinone ( 2 ), have been studied by FT-IR and FT-Raman spectroscopy. The spectra revealed the existence of two conformers for both compounds. A quantum chemical study of the title compounds was carried out at the B3LYP/6-311++G ∗∗ level of theory. The computed harmonic force fields were scaled utilizing previously developed scale factors resulting in good agreement with experiment and facilitating the assignment of the vibrational spectra and a distinction between the two conformers. The wavenumbers of identified OH torsional modes support a stronger intramolecular O–H⋯F hydrogen bonding in 1 than in 2 .

A comparative structural study on sodium and potassium N -chloroarenesulfonamidates has been carried out using X-ray diffraction and IR spectroscopy as experimental techniques. As shown by crystallographic studies, the sodium ions tend to incorporate more water oxygen atoms in their coordination spheres than the potassium ions, while the potassium congeners prefer the interaction with sulfonamidate moieties. The marked dissimilarity between the compositions of the coordination spheres as well as the different tendency of the sodium and potassium salts to absorb moisture from the air have been attributed to the different sizes of the sodium and potassium ions. The opposite shifts of the ν as (SO 2 ) and ν (SN) bands upon dehydration have been ascribed to an increased polarization of the sulfonyl group by the metal centers. Based on IR spectroscopic observations, a weakening of the N–Cl bonds is suspected in the water-free compounds, which may contribute to the known thermal instability of the dehydrated salts of N -chloroarenesulfonamides. Various sections of IR spectra as well as X-ray powder diffraction patterns have proved to be suitable to identify the water-free and hydrated samples.

Transition moment directions of the vibrational states of nitro and carbonyl groups of p-nitrobenzyl-16-mercaptohexadecanoate are evaluated by infrared linear dichroism (IR LD) to be further exploited as film orientation markers in self-assembled monolayers (SAMs) that the respective compound forms on metal surfaces. DFT calculations followed by a complete normal coordinate analysis were employed to assist in the vibrational bands assignments. The analysis of the experimental IR LD spectra in conjunction with the step-wise reduction procedure of Thulstrup–Eggers indicated that the transition moment directions of the antisymmetric NO2 stretching and the carbonyl stretching modes are collinear, and confirmed previous results that those of the symmetric and the antisymmetric NO2 stretching vibrations are not exactly mutually perpendicular.

A combined experimental and theoretical approach is presented to structural characterization of fairly large, newly synthesized organic molecules in order to enhance the effectiveness of their instrumental analysis by vibrational spectroscopy. The method consists of measurement of FT-IR and Raman spectra of the reaction products and subsequent ab initio or DFT quantum mechanical calculations (prediction) of the vibrational spectra for any anticipated structural varieties of the synthesized molecules. Comparison of the measured and computed frequencies as well as the observed and simulated spectra is performed to resolve any uncertainties in identifying the reaction products. Vibrational frequency and normal mode calculations based on scaled quantum mechanical (SQM) force fields performed at the DFT/B3LYP/6-31G* level of theory are demonstrated to provide a wealth of information that have been used in this work to ascertain the molecular structure, probable conformation and H-bond properties of three new isochromanone or coumarin derivatives, namely: 3-([2'-hydroxymethyl]-phenyl)-coumarin (1), E-4-(3'-hydroxyphenylmethylene)-3-isochromanone (2), and 2-[(2'-hydroxymethyl)phenyl]-3H-naphto[2,1-b]pyran-3-one (3).

Two corrosion products of zinc namely NaZn 4 Cl(OH) 6 SO 4 ·6H 2 O which occurs mainly in marine and traffic environments and Zn 4 Cl 2 (OH) 4 SO 4 ·5H 2 O which occurs in industrial, rural and urban environments were analysed using infrared and Raman spectroscopic methods and the vibrational modes of SO 4 2− ion, OH radical and H 2 O molecules have been identified and discussed. The symmetric stretching vibrations of the SO 4 2− ion of the compounds give an indication of the distorted structure for the SO 4 anion in the compounds, the distortion being more in Zn 4 Cl 2 (OH) 4 SO 4 ·5H 2 O. Due to the presence of strong hydrogen bond network, an unusual lowering of the symmetric stretching mode of SO 4 is observed in both the compounds. In NaZn 4 Cl(OH) 6 SO 4 ·6H 2 O, medium to weak hydrogen bonding network is present while strong to weak hydrogen bonding is present in Zn 4 Cl 2 (OH) 4 SO 4 ·5H 2 O.

The vibrational spectra of 3,4-diamino benzophenone (DABP) have been computed using B3LYP methodology and 6-31G* and 6-31G** basis sets. The solid phase FTIR and FT-Raman spectra were recorded in the region 4000-400 cm-1 and 3500-100 cm-1, respectively. A close agreement was achieved between the observed and calculated frequencies by employing normal coordinate calculations. The observed and simulated spectra were found to be well comparable.

The basic principles and methods of FTIR spectroscopy of the atmosphere were summarized in our previous paper 1. Thanks to the continuous technical development of FTIR spectroscopy (increasing throughput, dynamic alignment, more sensitive detectors, brighter sources, increasing scanning speed, development of focal plane array detectors, flexible spectral manipulations and data handling, etc.) in the last decade, this method has offered a great number of unique applications. In this review article, attempt to summarize the results of the most significant and frequent applications of FTIR spectroscopy to the study of the atmosphere. The possibilities of techniques applied in this field, the extractive and open path measurement methods, and the in situ IR absorption measurements such as remote sensing using the sun, the sky, or natural hot objects as IR sources of radiation are discussed. We have made a special focus to FTIR emission spectroscopy, the so‐called passive technique, since there are a n...

Vibrational analysis of the two conformers of furfural and 2-chlorobenzaldehyde has been carried out on the basis of their IR and Raman spectra measured in isotropic and anisotropic (nematic liquid crystalline) solvent. The average orientation of the individual conformers in the nematic solvent has been determined by means of a recently developed approach for low symmetry planar molecules using DFT calculations of the vibrational transitions moments. The complex shape of the carbonyl band additionally split into several components is interpreted as an effect of Fermi resonance.

The capabilities and limitations of on‐line FT‐IR spectroscopic detection during normal phase HPLC separation have been examined and evaluated as applied to a practical analytical problem, using a commercial IR micro flow‐through cell as an interface in conjunction with an up‐to‐date high speed, high sensitivity FT‐IR spectrometer, and dedicated data processing utilities. It has been shown that the usual chromatographic mobile phases containing polar modifiers can be used in such measurements, although the technique has definite limitations depending on the spectroscopic properties of the mobile phases and the analytes in question. In case of analytes having strong IR features in regions clear from mobile phase absorption, IR chromatograms are suitable for major component detection, whereas narrow‐region chemigram‐type detection tuned to selected absorption bands of the target compound is more successful than Gram‐Schmidt reconstructed chromatograms generated from full‐range IR spectra. Quantitat...

This work deals with the analysis of hydrogen bonding and the vibrational spectroscopy of 3,5-diamino-1,2,4-triazole by means of quantum chemical calculations. The mid and far FTIR and FT-Raman spectra were measured in the condensed state. The fundamental vibrational frequencies were calculated under different possible symmetries by applying the density functional theory with the B3LYP functional and the 6-31G* basis set. The results of the calculations obtained under C(2) symmetry produces the global minimum on the potential energy surface. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The infrared and Raman spectra were also predicted from the calculated intensities.

In recent years Fourier transform infrared (FTIR) spectroscopy has been the dominant technique used for measuring the infrared (IR) absorption and emission spectra of most materials, with substantial advantages in signal‐to‐noise ratio, resolution, speed, and detection limits. The major advantage of the FTIR technique over other spectroscopic methods is that practically all compounds show characteristic absorption/emission in the IR spectral region and based on this property they can thus be analyzed both quantitatively and qualitatively. The quest for highly sensitive detection methods for atmospheric trace gas samples, either in laboratory setup or in outdoor remote sensing, has been on agenda for several decades. The fast and intensive development of FTIR spectroscopic techniques has propelled the progress of trace gas analysis of the atmosphere. Since the early 1970s the number and scope of FTIR atmospheric measurements has increased steadily. In this review article we are making an attempt t...

The infrared and Raman spectra of resolved E and Z isomers of some 4-arylidene-3-isochromanone derivatives were analyzed with the aim of pointing out the differences in vibrational behavior of their coexisting stable conformers. Quantum mechanical (QM) density functional (DFT/B3LYP/6-31*) and normal coordinate calculations were carried out to establish the equilibrium structures and to facilitate the interpretation of the vibrational spectra of the 2′-pyrrolyl and 2′-nitrophenyl derivatives. The frequencies and intensities calculated according to the scaled quantum mechanical (SQM) force field method were used to simulate the IR and Raman spectra and compare them to the measured ones. The results demonstrate that the adopted methodology is capable of treating these fairly large polycyclic molecules. The resulting spectral simulations and detailed vibrational description can be highly useful in clarifying spectral differences brought about by cis–trans isomerism and indicating the extent of spectral changes due to further conformational changes of the aryl substituent attached to the olefinic CC bond.

The solid phase FT-IR and FT-Raman, solution phase linear dichroism IR (in nematic liquid crystal), and vapor phase GC/IR spectra of 2-(methylthio)benzonitrile have been recorded in the regions 4000–50, 3500–100, 4000–400, and 4000–650 cm −1 , respectively. The spectra were interpreted with the aid of normal coordinate analysis following full structure optimizations and force field calculations based on density functional theory (DFT) using standard B3LYP/6-31G* and B3LYP/6-311+G** method and basis set combinations. Normal coordinate calculations were performed with the DFT force field corrected by a recommended set of scaling factors yielding fairly good agreement between observed and calculated frequencies. IR dichroism data revealed an error in band assignment associated with a ν CS vibration, which could be eliminated only by introducing independent scaling factors for sulfur, whereas the overall frequency fit was further improved. Simulation of infrared and Raman spectra utilizing the results of these calculations led to excellent overall agreement with the observed spectral patterns, especially with the higher level basis set. The SQM approach applying selective scaling of the DFT force field was shown to be superior to the uniform scaling method in its ability to allow for making modifications in the band assignment, resulting in more accurate simulation of IR and Raman spectra including band polarizations and intensity patterns.

In this work the vibrational spectra of the monomethyl- and all possible dimethyl-derivatives of pyrazine are analyzed. The infrared and Raman spectra of the compounds have been recorded in condensed state, including Raman depolarization measurements in case of liquid materials. The optimized geometrical parameters and corresponding force fields of the investigated molecules have been calculated using the density functional theory with the Becke3P86 functional and the 6-311G (d,p) basis set. The resulting force fields were transformed to internal coordinates and the calculated vibrational frequencies and normal modes were utilized in the assignment of the observed vibrational fundamentals. The measured spectral data were used to refine the vibrational force constants by means of a small number of scale factors. After the refinement, the relative mean deviations between the measured and calculated frequencies were about 1% or less for every investigated molecule. Substituent effects on the vibrational modes are discussed in some detail. The analysis of the spectra led to a revised assignment for a number of bands.

A new procedure combining a known experimental approach with quantum chemical data is proposed for determination of the average orientation of planar molecules (possessing only C s symmetry) oriented in nematic solvents. It is based on quantum chemical calculation of the angle between two vibrational transition moments corresponding to in-plane vibrations giving rise to strong IR absorption bands with different dichroic ratios, which allows one to find the principal orientation axes of the oriented molecule. All other vibrational transition moments are then transformed into this coordinate system in order to obtain an improved description providing consistency between experimental and theoretical determinations of transition moment directions. The correction procedure is illustrated by the example of p -nitrobenzaldehyde.

A comparative study of the feasibility and efficiency of Raman spectroscopic detection of thin layer chromatography (TLC) spots of some weak Raman scatterers (essential amino acids, namely, glycine and L-forms of alanine, serine, valine, proline, hydroxyproline, and phenylalanine) was carried out using four different visible and near-infrared (NIR) laser radiations with wavelengths of 532, 633, 785, and 1064 nm. Three types of commercial TLC plates were tested and the possibility of inducing surface enhanced Raman scattering (SERS) by means of Ag-sol was also investigated. The spectra obtained from spotted analytes adsorbed on TLC plates were of very different quality strongly depending on the excitation wavelength, the wetness of the samples, and the compounds examined. The best results were obtained with the simple silica TLC plate, and it has been established that the longest wavelength (lowest energy) NIR excitation of a Nd:YAG laser is definitely more suitable for generating normal Raman scattering of analyte spots than any of the visible radiations. Concerning SERS with application of Ag-sol to the TLC spots, 1-3 orders of magnitude enhancement was observed with wet samples, the greatest with the 532 nm radiation and gradually smaller with the longer wavelength excitations. It is shown, however, that due to severe adsorption-induced spectral distortions and increased sensitivity to microscopic inhomogeneity of the sample, none of the SERS spectra obtained with the dispersive Raman microscope operating in the visible region were superior to the best NIR normal FT-Raman spectra, as far as sample identification is concerned.

b ), Istva ¬ n Sajo ¬ a ), Ja ¬ nos Kristo ¬f c Tetraamminecopper(2) bis(permanganate) ((Cu(NH3)4)(MnO4)2; 1) was prepared, and its properties were studied in both aqueous solution and the solid phase. The presence of H-bond interactions between the ammonia ligand of the complex cation and an O-atom of the permanganate ion was detected by IR and Raman methods. The solid-phase thermal deammoniation of 1 led to an unusual intramolecular redox reaction between the MnO¥¥¥H N linkage with formation of NH4NO3 and CuMn2O4-type mixed oxides instead of stepwise deammoniation, even below 100. The thermal deammoniation of 1 in aqueous solution led, instead of to hydrated copper(2) bis(permanganate), to the formation of NH4MnO4 (2). Since the temperature of the thermal deammoniation of 1 is lower than the decomposition temperature of the permanganate ion, the regulated solid-phase decomposition of 1 allowed preparation of CuMn2O4-type oxides with mixing of copper and manganese at the atomic level.

The solid and vapor phase IR and the solid phase Raman spectra of partially or fully resolved E - and Z -isomers of seven isochromanone derivatives were measured and analyzed with the aim of determining the differences in the vibrational behavior of the main rotational isomers. To aid spectral interpretation, quantum chemical and normal coordinate calculations were carried out for the 2′-furyl-substituted derivative, codenamed IK-14. The optimized molecular structures and corresponding force fields were calculated for four minimum energy configurations using the DFT/B3LYP/6-31 ∗ method. The vibrational frequencies and IR intensities were then calculated and fitted to the measured ones by the SQM force field approach. The calculations were highly successful in reproducing the frequencies and in clarifying the trends of changes brought about by cis – trans isomerism and other conformational changes. This resulted in a detailed vibrational assignment, and a common set of scale factors preferable for work with this type of molecules.

FT-IR, FT-Raman and FT-SERS spectra of 4-aminosalicylic acid sodium salt dihydrate (4ASAS) have been recorded and analysed. The vibrational bands due to NH2, OH, carboxyl group, and the benzene ring are identified. The CX ipb(17a, 17b), CC ipb(6,18a) and CH ipb (3,14a, 14b) bands are more enhanced in SERS. Broadening of the inplane carboxyl bend indicates interaction with the silver surface. Further the νCO, ν(CO)c and ν(CO)h are intense in the SERS spectrum. The rocking and wagging modes of NH2 also show up in SERS. The molecule (O, N donor ligand) is thought to adsorb through the carboxyl oxygen atom with the benzene ring in a ‘perpendicular side on orientation’ with respect to the silver surface.

The experimental infrared spectrum of 2,6-diisopropylphenol in dilute CCl4 solution displaying absorptions at 3619 (intense) and 3641 cm-1 (shoulder) in the O-H stretching region cannot be satisfactorily reproduced by two symmetric band components. Ab initio quantum chemical calculations have identified fiVe stable conformers differing in the relative orientations of the two ortho substituents, whereas DFT calculations yielded four different νOH frequencies for these conformers in agreement with the deconvolution and least-squares curve analysis of the experimental spectrum. The observed spectrum could be successfully simulated by the calculated frequencies and band intensities assigned to the five conformers on the basis of their relative stabilities.

The thermal evolution process of a Ta2O5 thin film from a TaCl5 precursor was followed by thermogravimetry combined with mass spectrometry. The TaCl5 coating was prepared by the deposition of disso...

Vibrational analysis of terephthalaldehyde (TPA) has been carried out on the basis of its IR and Raman spectra measured in isotropic and anisotropic (nematic liquid crystal) solvents. Polarization spectra were recorded for the purposes of the band assignment. Quantum chemical DFT (B3LYP/6-311G∗∗) calculations were performed for theoretical prediction of the band positions, intensities and polarization properties of IR absorption bands.

This work deals with the analysis of vibrational spectra of three five membered nitrogen heterocycles, the parent compounds: 1,2,3-triazole, 1,2,4-triazole and tetrazole, and their N-deuterated derivatives. The infrared spectra of these compounds were recorded in condensed states, while the Raman spectra were measured without polarization and using both parallel and perpendicular polarizations of scattered light. The fundamental vibrational frequencies were calculated applying the density functional theory with the Becke3P86 functional and the 6-311G(d,p) basis set. The results of the calculations were utilized in the assignment of the vibrational fundamentals, and the measured fundamental frequencies were used to refine the vibrational force constants. The considerable association of these compounds in condensed phase caused shifts of some fundamental frequencies of the isolated molecules. Nevertheless, the relative mean deviations between the measured and calculated frequencies were about 1 % or less for every investigated molecule.

The vibrational properties of 2-nitroresorcinol have been studied by a combined experimental and theoretical analysis. The FT-IR and FT-Raman spectra of the compound have been recorded in the mid- and far-IR range (4000–150 cm−1). Symmetry related experimental information was obtained from polarisation IR and Raman measurements. The interpretation of the spectra was aided by quantum chemical calculations carried out at the B3-LYP/6-31G* level. Both the spectra and calculations support the C2v structure of the molecule with a symmetric intramolecular –O–H ⋯ O–N–O ⋯ H–O– hydrogen bonding interaction. The deficiencies of the computations for the molecular vibrations were corrected by the scaled quantum mechanical (SQM) method of Pulay. Using the standard scale factors developed for B3-LYP/6-31G* force fields, an rms deviation of 9.7 cm−1 was achieved between the gas-phase experimental and SQM frequencies. As a result of our SQM analysis, all the 42 fundamentals of the molecule were assigned. A comparison with the analogous hydrogen bonding moiety in 2-nitrophenol indicates a somewhat stronger hydrogen bonding interaction in the title molecule. This is accompanied, however, by an increased strain in the six-membered –C–O–H ⋯ O–N–C– rings.

A case of “disappearance” of the usually strong, characteristic carbonyl band in infrared absorption spectrum of a fused three-ring compound, Uhle's ketone, on oxidation (dehydrogenation) is examined by means of the scaled quantum mechanical force field method using semiempirical AM1, ab initio RHF/3-21G, and density functional B3LYP/6-31G* calculations followed by full normal coordinate analysis. The study confirmed the presence of the keto form in solution characterized by extensive coupling of the carbonyl vibration with skeletal modes leading to lower than usual frequencies and highly reduced band intensities. The results indicate that only the highest level calculations are of real help in explaining this unusual spectral behavior by clarifying the fine details of vibrational assignment.

Infrared linear dichroic (IR-LD) spectra of three substance (2-naphthaldehyde, terephthalaldehyde and terephthalophenone) whose molecules give rise to two conformers were studied in the present article. It was aimed to understand how both conformers of each molecule orient in a nematic solution and could they be distinguished by means of IR-LD spectra. For this purpose the substances to be studied were dissolved and oriented in the nematic phase ZLI-1695 (Merck). The results thus obtained show that IR-LD spectra can help in distinguishing between the spectral bands of the conformers.

Infrared linear dichroism (IR-LD) measurements and ab initio and density functional (DFT) frequency and intensity calculations were performed on p -X-nitrobenzenes (X=F, Cl, Br, CH 3 and CHO). Simulation of the reduced IR-LD spectra using DFT (B3LYP/6-311G**) calculated band parameters led to excellent agreement between theory and experiment.

FT-IR (gas, solution, solid) and FT-Raman (solution, solid) spectra of 2-nitrophenol have been recorded in the range of 4000–30 cm−1. The spectra were interpreted with the aid of normal coordinate analysis based on a scaled Becke3–Lee–Yang–Parr/6-31G* density functional force field utilising a set of scale factors introduced recently by Rauhut and Pulay (G. Rauhut, P. Pulay, J. Phys. Chem. 99 (1995) 3093). These scale factors, developed on a small training set of organic molecules containing no hydrogen bonding moieties, were found to be well transferable to 2-nitrophenol including the strong intramolecular (O)H⋯O(N) hydrogen bonding moiety as well. The scaled force field reproduced the experimental frequencies of the molecule by a weighted mean deviation of 10.5 cm−1. Based on the calculated results, 38 fundamentals from a total of 39 were identified and assigned, revising the assignments of earlier experimental studies for several fundamentals.

The assignment of the vibrational spectra of phenol has been reexamined on the basis of Raman and new IR measurements and theoretical analysis of the normal modes of vibrations in the electronic ground state. The infrared spectra of C6H5OH, C6D5OD, and C6D5OH have been studied in solution and vapor phases, as well as has the Raman spectra in solutions. New experimental data were obtained from infrared linear dichroism (IR-LD) studies of phenol aligned in uniaxially oriented nematic liquid crystal solution. The measured dichroic ratios and orientation factors indicate an effective Cs symmetry of the molecule with coplanar orientation of OH bond with the benzene ring and supply unique information on the extent of symmetry lowering of benzene normal modes. The fundamental vibrational frequencies, force constants, and dipole derivatives have been calculated by ab initio quantum chemical methods applying the B3P86 density functional approximation with 6-311G** basis set. The force field optimized by means of a...

This is a preliminary report of our research aimed at the joint use of up-to-date experimental (polarized infrared spectra of oriented samples) and theoretical (ab initio quantum chemical) methods of determining the vibrational electric transition moment directions to help in the assignment of infrared absorption spectra of polyatomic molecules. The systems studied include ethylene, p -nitrobromobenzene, thiosemicarbazide and N , N -dimethyl- S -methylmonothiobarbamate. Our results show that this bilateral approach works well for molecules with orthogonal ( C 2 ν or higher) symmetry. Special emphasis was given to testing the capabilities of the method for systems with lower symmetry ( C 2h , C s , etc.) where it proved to be no more successful than the prediction of infrared intensities: agreement between the calculated and measured band polarization values within tight limits is quite rare, while completely wrong results have also been obtained, especially in the presence of unaccounted hydrogen bonding.

Fourier transform infrared emission spectroscopy, FT-IRES, was used for the detection of adsorbed CO species at p = 40 mbar and T = 333–393 K on metal powders (Pt, Pd, Rh) and supported catalysts (Rh/activated carbon, 5% Rh). Linearly bonded CO features were detected at 2020 and 2030 cm−1 for Pd and Pt respectively. Bridged carbonly species were also detected for Pd and Pt at 1930 and 1920 cm−1 respectively. The bands observed for Rh powder at 2040 and 1970 cm−1 have been assigned to symmetric and asymmetric stretchings of the geminal dicarbonyl, and the band at 1860 cm−1 is ascribed to the bridged carbonyl species. Similar bands, but about ten times weaker, have been observed for carbon supported Rh, and an extreme feature appeared at about 1800 cm−1 that might indicate the existence of three-fold bridged species.

In order to clarify the nature of coupling of vibrational coordinates of the azo group with its surrounding, the molecule of trans-azobenzene (tAB) was chosen. It is interesting to compare this coupling with those of isoelectronic compounds containing two phenyl groups connected to a bridging group, such as cis-stilbene (cSB), trans-stilbene (tSB) and trans-N-benzylideneaniline (tBA), already treated by our group. trans-Azobenzene molecule belongs to the C_2h point group with four symmetry species: a_g (Raman active, in-plane), a_u (infrared active, in-plane), b_g (Raman active, out-of-plane) and b_u (infrared active, out-of-plane). In the FT Raman spectrum of powdered tAB a very strong Raman band (a_g) was found at 1440 cm(-1), having no a counterpart in the infrared spectrum. Since it is shifted to 1428 cm(-1) in (N-15)-tAB, it was assigned to the N=N stretching mode. This is a very low value in comparison with 1630 cm(-1) (C=C str.), 1639 cm(-1) (C=C str.) and 1626 cm(-1) (C=N str.) in neat cSB, tSB and tBA, respectively. However, in (D_10)-tAB the strongest Raman band appears at 1466 cm(-1) without any stronger band around. The normal coordinate calculations of tAB, using the AM1 procedure, indicate a substantial contribution to the N=N stretching from the phenyl group mode 19b. In the case of (D_10)-tAB the N=N mode is decoupled, because the light phenyl groups are substituted by the heavy ones, which increases the N=N stretching frequency. Another indication of the strong coupling of azo and phenyl modes in tAB is the appearance of numerous bands in the infrared spectrum of 4-D-tAB (C_S point group) in comparison with tAB itself (C_2h). Such an activation of infrared absorptions was not observed in analogous cSB, tSB and tBA isotopomers.

The IR and polarized Raman spectra of a single crystal RbAl(SO 4 ) 2 ·12H 2 O is recorded and analyzed at room temperature. Bands indicate a stronger S–O bond in RbAl(SO 4 ) 2 ·12H 2 O than that in a free SO 2− 4 ion. The fraction of reversed sulfate group in the Rb alum is much lower than that in the potassium alum. Broad bands with frequencies considerably shifted from the free state values indicate that water molecules form hydrogen bonds of various strengths. Two crystallographically distinct water molecules are identified in the crystal.

Recent advances in FT-IR emission spectroscopy of solids are briefly reviewed, and some neglected points concerning the measurement of blackbody radiation are dealt with. A corrected equation describing the single-beam emission spectra is given, taking into account the possible thermal radiation of the detector. Similarities between the effect of self-absorption and that of illegal data manipulations on emittance spectra are pointed out, both giving rise to spectral distortions like inverted or split peaks or altered band shapes and intensities. To avoid some of these problems, the use of a linear emission intensity scale, emissivity, is advocated, especially for quantitative work. A special case of self-absorption, namely, that of multilayer samples, is discussed, in which the spectral distributions of emitted and absorbed radiation are significantly different. Simulations of the emission-absorption spectra observed in such cases are shown to help with spectral and structural interpretation.

Infrared and polarized Raman spectra of a single crystal Rb 3 H(SeO 4 ) 2 and the polycrystalline spectra of its deuterated analogue are recorded and analysed. Bands indicate the existence of SeO 4 4− ions and HSeO 4 ions, in agreement with a non-centrosymmetric dimer in the crystal. The difference between ν(Se-OH) and ν(Se-OH) bands is a measure of the hydrogen bond strength and it decreases on deuteration. The presence of an absorption continuum along with a transmission window shows that the proton motion is coupled with those of the oxygen atoms in the SeO 4 2− ions. The ABC bands in the OH stretching region also support strong hydrogen bonding in the crystal. The lower wave numbers for the stretching OH mode show that the dimer formation is quite anharmonic, as judged from the isotopic shift.

The vibrational analysis of cis -stilbene in the ground electronic state based on the infrared and Raman spectra of a series of its isotopomers and scaled semiempirical AM1 calculations is reported. The C α C α stretching, all the four C α H deformations and the C α C α torsion are described. A comparison with trans -stilbene shows a much lesser degree of couplings between olefinic and phenyl vibrations in cis -stilbene.

A new analytical approach for improving the precision in determination of vibrational transition moment directions of low symmetry molecules (lacking orthogonal axes) is discussed in this paper. The target molecules are partially uniaxially oriented in nematic liquid crystalline solvent and are studied by IR absorption spectroscopy using polarized light. The fundamental problem addressed is that IR linear dichroism measurements of low symmetry molecules alone cannot provide sufficient information on molecular orientation and transition moment directions. It is shown that computational prediction of these quantities can supply relevant complementary data, helping to reveal the hidden information content and achieve a more meaningful and more precise interpretation of the measured dichroic ratios. The combined experimental and theoretical/computational method proposed by us recently for determination of the average orientation of molecules with Cs symmetry has now been replaced by a more precise analytical approach. The new method introduced and discussed in full detail here uses a mathematically evaluated angle between two vibrational transition moment vectors as a reference. The discussion also deals with error analysis and estimation of uncertainties of the orientational parameters. The proposed procedure has been tested in an analysis of the infrared linear dichroism (IR–LD) spectra of 1-D- and 2-D-naphthalene complemented with DFT calculations using the scaled quantum mechanical force field (SQM FF) method.

Starting from 7-methoxytryptamine (7) with the use of the method we developed earlier, (±)-cuanzine (1),(±)-decarbomethoxyapocuanzine (4), and their epimers 5 and 22 were synthesized.

The IR (3200–30 cm−1) spectra have been recorded for S-methyl-N,N-dimefhylthiocarbamate, (CH3)2NC(O)SCH3, and its isotopomers, S-d3, N-d6 and N-d9, for the gas and liquid. Additionally, the Raman spectra (3200–10 cm−1) for the solid and liquid, with qualitative depolarization ratios, have been obtained for all the isotopes. These data are interpreted on the basis that the s-cis conformer (the S-methyl group oriented eis to the carbonyl group) with Cs symmetry is the only form existing in all three phases for this molecule. A complete vibrational assignment proposed for the -d0 molecule is facilitated by the availability of spectral data for five different isotopomers. A normal coordinate analysis has been carried out utilizing ab initio calculations with the 3–21G* basis set. The potential energy distributions and ab initio calculated frequencies have allowed a clarification of some of the corresponding results obtained from experiment. Structural optimizations and potential surface scan have also been carried out by ab initio calculations with the 3–21G* basis set. These results are compared with some previous studies on this molecule as well as on similar molecules.

The practical aspects of infrared emission spectroscopy are reviewed briefly, with emphasis on recent developments and on special problems encountered in measurements of adsorbed species on opaque substrates. A few examples are given for cases when the species of interest give rise to inverted emission bands on the background of substrate emission. The feasibility of recording IR emission spectra of adsorbates on metal powders is demonstrated.

Vibrational frequency data on CO adsorption on pure Pd powder have been obtained by IR emission technique and are compared with those available for evaporated Pd films and Pd single crystal surface from IR transmission and reflection-absorption measurements.

IR and Raman spectra of Te(OH)6.2NH4H2AsO4.(NH4)2HAsO4 (compound I) and Te(OH)6.2(NH4)2HAsO4 (compound II) are recorded and analysed. The symmetry of different groups and the vibrational interaction between them are discussed. The observed spectra suggest the existence of HAsO2−4 in II and coexistence of HAsO2−4 and H2AsO−4 in I. The ammonium ion is found to execute hindered rotation in the lattice in both the compounds.