The infrared and Raman spectra of pyromellitic dianhydride

The infrared and Raman spectra of solid state samples of pyromellitic dianhydride have been measured. The infrared—Raman mutual exclusion rule has been observed and the frequencies have been tentatively assigned on the basis of D_2h symmetry. The values of the CO and skeletal ring stretching frequencies have been interpreted in terms of a conjugated π-system.     

The infrared and Raman spectra of guanidinium salts

The i.r. and Raman spectra of guanidinium chloride, guanidinium perchlorate, and the deuterated derivatives of these salts, have been determined as solids and in solutions.     

The infrared and Raman spectra of carbonyl diisocyanate

The infrared and Raman spectra of carbonyl diisocyanate have been recorded. Vibrational assignments have been made on the basis that two planar conformations are present both in the liquid and vapour phases: cis—cis and cis—trans. Simple normal coordinate calculations have been used to confirm the assignments.     

The infrared and Raman spectra of octachloro- and octabromocyclotetrasilane

The infrared and Raman spectra of cyclo-Si₄Cl₈ and cyclo-Si₄Br₈ have been measured and assigned. The selection rules indicate that the Si₄ ring is not planar. A normalcoordinate analysis (NCA) has been performed. The SiSi stretching-force constants are calculated to be 1.75–1.5·10² Nm^?1 and are lower than in the corresponding perhalogenated five- and six-membered rings. The SiCl and SiBr force constants seem to be somewhat higher (2.7–2.35·10² Nm^?1).     

The laser Raman and infrared spectra of crystalline dibenzyl

The Raman spectrum of crystalline dibenzyl has been excited with a 50-mw He-Ne laser (6328 Å) and thirty one Raman bands have been recorded. The far infrared spec trum which reveals six absorptions in the 10–270 cm⁻¹ region and the infrared spectrum from 300–3200 cm⁻¹ have been observed, and correlations with the Raman frequencies have been established. Assignments of some of the characteristic frequencies have been made, and the implications of the data regarding the geometry of the molecule are discussed.     

The Fourier Transform Raman and infrared spectra of naphthazarin

The FT Raman spectra of the three naphthazarin polymorphs have been recorded for the first time and compared with the FTIR spectra of the polymorphs and of naphthazarin with deuterated hydroxyl groups. It is possible to distinguish between the polymorphs, to deduce that the room temperature static symmetry point group of naphthazarin is C_2v, to assign the ν(CH), σ(OH), γ(OH) vibrations and to confirm the absence of the ν(OH) mode.     

Raman and infrared spectra of crystalline fluoroform

Raman and far-infrared spectra of crystalline fluoroform at temperatures between 20 and 106 K have been recorded. There is no evidence for any solid-state phase transitions, nor for hydrogen bonding. The rich lattice spectra and crystal field splittings suggest that the unit cell is rather large, and possible structures are discussed.     

Raman and infrared spectra of crystalline chloroform

Raman and far-infrared spectra of polycrystalline samples of chloroform at 20 and 80 K are reported. Crystal field spilttings of the intramolecular fundamentals are observed as well as nine Raman and six infrared lattice modes. Spectra are interpreted in terms of a group theoretical analysis based on the molecular and crystal symmetries.     

The molecular structure and infrared and Raman spectra of SCCCS

The structure, rotational constants, and vibrational spectra of SCCCS have been predicted by ab initio and density functional quantum mechanical methods. Basis sets ranging in size from double-ζ plus polarization (DZP) to triple-ζ plus double polarization, augmented with f functions (TZ2Pf) were employed. Our theoretical results are in agreement with experiments for both the geometrical structure and most of the fundamental frequencies that have been observed. An exception occurs for the SCC bending frequency υ₅, for which the 1966 and 1972 assignments of Bates and Smith appear superior to the 1966 Smith and Leroi Raman assignment, accepted in the definitive recent studies of Holland and Winnewisser. We present results for four isotopomers of SCCCS that have not yet been observed in the laboratory.     

Raman and infrared spectra of lanthanum molybdate

The infrared and Raman spectra of gel-grown lanthanum molybdate were recorded. Group theoretical analysis was carried out and a vibrational assignment proposed based on C_2h symmetry. Factor group and site effects are discussed.     

The polarized infrared and Raman spectra of crystalline ammonium trifluoromethanesulphonate

The infrared and Raman spectra of NH₄CF₃SO₃ were obtained and analysed and an assignment was proposed for the observed bands. The assignment of some anion bands was supported by means of the polarized spectra of monocrystals. The fundamental frequencies of the anion were used for a normal coordinate calculation.     

The infrared and Raman spectra of 2,4-and 2,5-dimethylbenzaldehydes

The vibrational frequencies of 2,4-and 2,5-dimethylbenzaldehydes have been reported from the study of ir absorption and Raman spectra of these molecules recorded in liquid phase. The probable assignments for all the frequencies are presented in terms of the fundamentals, overtones or combinations     

Laser Raman and infrared spectra of deuterated silylgermanes

The laser Raman and infrared spectra of deuterated silylgermanes have been recorded on a Cary model 82 grating spectrophotometer with an argon laser source and a Perkin—Elmer 983 double beam grating spectrophotometer, respectively. The spectra have been analysed on the basis of fundamental combinations and overtones and the frequencies have been assigned to various modes of vibration, assuming C_3υ point group symmetry. Furthermore, based on the force field for silylgermanes, the vibrational frequencies of isotopically substituted species have been calculated and the results are briefly discussed.     

Raman and infrared spectra of some tetrahalide crystals

Recent Raman and infrared spectra of a number of tetrahalide crystals are reported. While some examples of isotopic and crystal field splittings of the internal molecular modes are included, the emphasis is on the external lattice vibrations which are important for investigations of intermolecular forces and lattice dynamics calculations. Because of the weak signals from these non-polar near-spherical molecules and other experimental difficulties, these modes have not been investigated in detail in earlier work. Examples to be discussed include CCl₄, CBr₄ and CF₄, all of which exhibit solid state phase transitions; the tetrachlorides of Ge, Ti, Si and Sn, all of which are thought to have similar crystal structures; and SnBr₄, the structure of which is accurately known and is used as a basis for lattice dynamics calculations.     

Raman,resonance Raman and infrared spectra of potassium uranyl croconate

The Raman, resonance Raman and IR spectra of potassium uranyl croconate, UO₂(H₂O)K₂(C₅O₅)₂ were obtained and interpreted. Several croconate modes are split indicating a substantial decrease in the oxocarbon symmetry, as is to be expected from a recent crystallographic investigation, revealing the coordination of the oxocarbon to be two non-equivalent UO²⁺₂ moieties in a monodentate fashion. In terms of vibrational frequency shifts it can be concluded that the UO²⁺₂ moiety behaves as an isolated oscillator.The resonance Raman results suggest that the strong band centered around 450 nm in the UV—vis spectrum should be assigned to a charge transfer transition from the oxocarbon to the uranyl ion. In fact, as resonance is approached, both uranyl and croconate modes are enhanced. It can also be inferred that the chromophore is rather delocalized into the oxocarbon ring, rather than localized in the carbonyl groups as previously observed for other croconate complexes.     

Automatic reduction and evaluation of infrared and Raman spectra

Summary The automatic interpretation of digital recorded infrared and Raman spectra is described. The procedure starts with the automatic correction for an approximated base line. In the case of Raman spectra the spectral response of the spectrometer is corrected, too. Subsequently, the spectra are reduced to band lists, conserving the position, intensity and half-widths of the bands. These band lists are the input in an interpretation algorithm for the combined evaluation of infrared and Raman spectra by testing presence or absence of characteristic bands or groups of bands. The algorithm was tested with 300 substances. A balance of the interpretation results shows that the abscence of structural elements is found more safely than the presence. The algorithm may be modified for special purposes: evaluation of infrared or Raman spectra alone or application to special classes of substances.

---

Automatische Reduktion und Auswertung von IR- und Raman-SpektrenI. Interpretation charakteristischer Banden

Zusammenfassung Ziel dieser Arbeit ist die automatische Interpretation von Infrarot- und Raman-Spektren mit Hilfe charakteristischer Banden. Die Bearbeitung der Spektren beginnt mit der Korrektur der digital registrierten Spektren auf eine angenÄherte Grundlinie. Bei Raman-Spektren wird zusÄtzlich die spektrale Empfindlichkeit des Spektrometers korrigiert. Die Spektren werden auf Bandenlisten reduziert, in denen die Lage, IntensitÄt und Halbwertsbreite der einzelnen Banden enthalten sind. Diese Bandenlisten dienen als Eingabe in einen Interpretationsalgorithmus mit dem durch Prüfung der Lage und IntensitÄt einzelner charakteristischer Banden und Bandengruppen auf Anwesenheit oder Abwesenheit von Strukturmerkmalen geschlossen wird. Der Algorithmus wurde an 300 Substanzen getestet. Die Aussage über das Fehlen bestimmter Gruppen ist sicherer als die über deren Vorhandensein. Die Struktur des Auswertealgorithmus erlaubt ein einfaches Anpassen an verschiedene Anwendungsgebiete: Auswertung von Infrarot-oder Raman-Spektrum allein, bzw. Anwendung bei speziellen Substanzklassen.

     

Raman and infrared spectra of methylmercury complexes of adenine

The i.r. and Raman spectra of four crystalline methylmercury complexes of adenine have been recorded. Three of these complexes, substituted or coordinated at positions N9, N7/N9, and N3/N7/N9, have well-characterized crystal structures. The last one is probably N6/N7/N9-metalated. The spectra of these complexes, as well as those of adenine, are compared in an attempt to establish correlations between these spectra and the sites of complexation in the derivatives.