Infrared and Raman spectra of ethylene trithiocarbonate complexes of some Zn(II), Cd(II) and Hg(II) halides

Coordination compounds of ethylene trithiocarbonate (ETTC) with some Zn(II), Cd(II) and Hg(II) halides have been prepared, characterized and their infrared and Raman spectra recorded. The i.r. spectra in the range 4000-400 cm⁻¹ suggest that the organic ligand is bonded to the metal ions through its exocyclic sulphur atom, whereas the far-i.r. and Raman spectra show that the complexes of the type HgX₂(ETTC) (X = Cl, Br or I) possess a trans dimeric halogen-bridged structure. The Cd(II) and Zn(II) species are of the type MX₂(ETTC)₂ and they possess a pseudotetrahedral structure of C_2υ symmetry.     

Vibrational spectra and structure of the heptahydrodiborate ion, [B2H7]− in glycol ethers

The i.r. and Raman spectra of the heptahydroborate ion, [B₂H₇]⁻, and its deuterated derivative, [B₂D₇]⁻, have been obtained in solution and assignments have been made of the observed bands. The data are interpreted as indicating a bent C₂ structure in solution. Normal coordinate calculations based on this model are presented.     

Vibrational spectra and normal coordinate calculations for trimethylselenonium-d0 and -d9 ions and dimethyl selenide-d0, -d6

The i.r. (4000-30 cm⁻¹) and Raman (4000-0 cm⁻¹) spectra of trimethylselenonium iodide and dimethyl selenide have been obtained, together with those of their deuterated analogues. All the active fundamentals of the trimethylselenonium ion have been assigned, assuming C_3ν molecular symmetry. Normal coordinate calculations have been carried out for the trimethyl-selenonium ion and dimethyl selenide and the SeC force constants of both the compounds are compared, including those of other corresponding chalcogenides.     

Vibrational spectra and normal coordinate calculations for dimethyltelluride-d0, -d6 and dimethyltellurium difluoride-d0, -d6

The i.r. (4000-30 cm⁻¹) and Raman (4000-O cm⁻¹) spectra of dimethyltelluride, dimethyltellurium difluoride and their deuterated analogs have been obtained. All the active fundamentals of these compounds except methyl torsions were assigned, assuming a C_2υ molecular symmetry for both the tellurides. Normal coordinate calculations have been made in order to confirm the proposed assignments. The skeletal bond strength of the tellurides together with that of TeF₄ are discussed, using the valence stretching force constants.     

Vibrational (i.r. and Raman) spectra and conformational studies of 1-formyl-3-thiosemicarbazide

The i.r. and Raman spectra (30–4000 cm⁻¹) of 1-formyl-3-thiosemicarbazide (FTSC) and deuterated ftsc-d₄, have been studied. Most of the vibration modes reveal pairs of bands and show strong temperature dependence. A band group {ν(NNH₂)} at ∼ 1100 cm⁻¹ exhibits well resolved doublet (1095 and 1112 cm⁻¹) structure below 100 k. The intensity in the 11 12 cm⁻¹ band decreases regularly (band disappears at 150 K) with the rise in temperature. Two new bands at 955 and 1070 cm⁻¹ appear while measured above 400 K. The system eventually exists in several conformers in simultaneous equilibria. Moreover, a few bands {e.g. ν(CO), ν(CS) and ν(CH)} that show strong intensifies in i.r. exhibit weak (or zero) intensifies in the Raman and vice-versa. The features (characteristic of u and g vibration species) could be explained by a C_2h pseudo symmetry space group proposed for the system. Both the FTSC and FTSC-d₄ represent strong molecular associations. This favours the maximum abundance in the dimer stabilized conformers.     

The spectra and structure of sulphur-containing organic compounds—V. The vibrational spectra and conformations of p-RC6H4SO2CH2X sulphones

The i.r. and Raman spectra of p-RC₆H₄SO₂CH₂X (R = H, CH₃, Cl, Br; X = Cl, Br) sulphone liquid solutions and crystals have been investigated. The existence of a mixture of trans and gauche conformations in liquid and solution phases has been established. The temperature dependences of the i.r. spectra have been studied and the values of ΔH = H (gauche) - H(trans) determined. The molecular conformations in the crystal have been determined by the dichroism of polarized i.r. spectral bands. In the case of CH₃C₆H₄SO₂CH₂Br polymorphic crystal modifications, differing in molecular conformations, have been found. An interpretation of the vibrational spectra is given. See Part IV, A. B. REMizov, F. S. BILALOV and 1. S. POMINOV, Spectrochim Acta, in press.     

Vibrational spectra of tetramethyleyclobutane-1-one-3-thione and the fully deuterated derivative

Raman and i.r. spectra of tetramethylcyclobutane-1-one-3-thione (TMCBOT) and the fully deuterated derivative TMCBOT-_d¹² have been recorded. A fairly complete set of vibrational frequencies and assignments are given for the two molecules. The CO stretching mode was observed as a very strong Fermi doublet in the infrared spectrum of TMCBOT at 1811/1782 cm⁻¹. For TMCBOT-d₁₂ a similar doublet was observed at 1808/1775 cm⁻¹. The CS stretching mode was assigned to bands at 1303 cm⁻¹ for TMCBOT and 1307 cm⁻¹ for the deuterated molecule.     

Frequences infrarouges et Raman caracteristiques de cyclopropyl- et (cyclopropylmethyl)trimethylsilanes: Comparaison avec les vinyl- et allyltrimethylsilanes—III

The i.r. and Raman spectra of 20 compounds with a trimethylsilyl group linked to either a cyclopropane ring or a vinyl or allyl radical have been recorded between 400 and 4000 cm⁻¹. The experimental results and the vibration frequency assignments, especially the symmetrical SiC_n stretching, show that there are two classes of derivatives characterized by analogous SiC spectra: (1) the vinyl- and cyclopropyltrimethylsilanes and (2) the allyl- and (cyclopropylmethyl)trimethylsilanes. The spectroscopic behavior of each class is consistent with its observed chemical reactivity. A distinction can also be made between some structural isomers on the basis of the SiC stretching or other frequencies.     

Vibrational states of chlorophyll and related compound molecules. Metal complexes of octaethylchlorin

Fine-structure fluorescence spectra and i.r. spectra of the model compound chlorophyll-Zn-octaethylchlorin (Zn OEC), and its three deuterated derivatives at meso-positions and Zn OEC-¹⁵N₄ have been obtained. Polarization measurements for individual zero-phonon lines show that in the vibronic spectra of the above compounds the totally symmetric vibrations are mainly active. A joint analysis of the experimental data and calculation results of normal vibrations has served as a basis for the interpretation of the spectra obtained as well as resonance Raman spectra. It is pointed out that the vibrations of ethyl substituents largely form a vibrational structure of the vibronic Zn OEC spectrum. An assignment of some lines in a fine-structure spectrum of chlorophyll a is discussed.     

Conformational equilibrium of dicyclopropyl ketone

The i.r. and Raman spectra of liquid dicyclopropyl ketone have been reinvestigated from 4000 to 200 cm⁻¹ with higher resolution than previously obtained. In addition, the i.r. spectrum of the polycrystalline solid was recorded from 4000 to 400 cm⁻¹. Contrary to published results, evidence has been obtained for a conformational equilibrium between the predominant cis—cis form and the gauche—gauche conformer.     

Spectra and structure of organophosphorus compounds—XXX. Vibrational and conformational study of methoxy difluorophosphinoxide-d0 and -d3

The i.r. (4000-40 cm⁻¹) and Raman (4000-10 cm⁻¹) spectra of gaseous, liquid and solid methoxy difluorophosphinoxide, CH₃OP(O)F₂, and the deuterated analog have been recorded. Results obtained from variable solvent and matrix isolation studies are consistent with the existence of both trans (CO bond trans to the PO bond) and gauche (dihedral angle approximately 120° from the trans form) conformers in the fluid phases. From simulations of observed gas phase i.r. band profiles, it was possible for assignments to be made to the individual conformers for a number of the fundamentals. Variable temperature studies carried out for the gaseous and liquid phases give energy differences between the gauche and trans conformers of 451 ± 100 cm⁻¹ (1.29 ± 0.3 kcal/mol) and 69 ± 20 cm⁻¹ (197 ± 57 cal/mol), respectively. Furthermore, these data are consistent with the gauche form being the thermodynamically preferred conformer for the gas phase whereas the trans conformer is preferred in the liquid phase and the only conformer present in the annealed solid. The methoxy torsional mode of the gauche conformer has been assigned to a very strong band observed in the far i.r. spectrum of the gas phase at 42 cm⁻¹. The matrix isolation spectra of the normal compound in Ar, CO and N₂ matrices indicated no changes in the conformational equilibrium among these different matrices and this equilibrium remains unchanged upon annealing the matrices.     

Asymmetric torsional potential function and conformational analysis of furfural by far infrared and Raman spectroscopy

The far i.r. (400-50 cm⁻¹) spectra of gaseous and solid furfural (2-furancarboxaldehyde), c-C₄H₃O (CHO), have been recorded. Additionally, the Raman (3500-20 cm⁻¹) spectra of the gas and liquid have been obtained at variable temperatures and the spectrum of the solid at 25 K. These data have been interpreted on the basis that the molecule exists in two different conformations in the fluid states and that the conformation which has the two oxygen atoms oriented in a trans configuration, OO-trans, is most stable (ΔH ⩽ 1 kcal/mol) in the gas; however, the conformation which has the two oxygen atoms oriented cis, OO-cis, is preferred in the liquid (ΔH = 1.07 ± 0.03 kcal/mol) and is the only rotamer present in the spectra of the solid. The asymmetric torsional fundamental for the OO-trans rotamer has been observed at 146.25 cm⁻¹ in the far i.r. spectrum of the vapor and has five accompanying “hot bands”. The corresponding fundamental for the OO-cis rotamer has been observed at 127.86 cm⁻¹ along with a “hot band” which occurs at 127.46 cm⁻¹. From these data a cosine-based potential function governing internal rotation of the CHO top has been determined and the potential coefficients have values of V₁ = 173 ± 2, V₂ = 3112 ± 20, V₃ = 113 ± 2 and V₄ = −198 ± 6 cm⁻¹. This potential is consistent with an enthalpy difference between the more stable OO-trans and high energy OO-cis conformers being 286 ± 24 cm⁻¹ (818 ± 67 cal/mol) and a trans to cis barrier height of 3255 ± 20 cm⁻¹ (9.31 ± 0.06 kcal/mol). These results are compared to the corresponding quantities obtained previously from microwave spectroscopy and theoretical methods.     

A correlation between crystallographic and spectroscopic data for some eulytite-type phosphates containing bismuth

The i.r. and Raman spectra of some Eulytite-type phosphates containing bismuth have been recorded and analyzed. The spectra have been interpreted on the basis of the “site symmetry” analysis. A correlation between the symmetric stretching ν₁ mode (Raman active) and the volume of the lattices has been found.     

Vibrational spectrum of KMIIP3O9 tricyclophosphates with the benitoite structure

The Raman and i.r. spectra of tricyclophosphates KM^IIP₃O₉ (M^II = Mg, Ca, Co, Mn, Zn, Cd) with the benitoite structure are discussed on the basis of a factor group analysis, and by comparison with the spectrum of the structurally related LaP₃O₉. 3 H₂O. Most of the stretching frequencies have been observed and assigned, whereas the assignment of the bending modes remains more or less hypothetical. Low-frequency i.r. bands have been assigned to translations of either K or M^II cations on the basis of mass effects. The influence of the ring chain polymorphism is briefly discussed.     

1064-nm-excited Fourier transform Raman studies of bacteriochlorophyll-a in solid films and in a blue-green mutant of Rhodobacter sphaeroides

1064-nm-excited Fourier transform Raman spectra of bacteriochlorophyll-a (BChl) in various solid films and in chromatophores from a blue-green mutant of Rhodobacter sphaeroides have been obtained. The observed Raman spectra are free from high fluorescence backgrounds and sample degradation. The observed intensities seem to be enhanced because of a pre-resonant effect between the exciting radiation at 1064 nm and the Q_y absorption at 770–870 nm of BChl. The spectral features are substantially different from the Soret and Q_x resonance Raman spectra extensively investigated so far; several bands in the wavenumber region lower than 1200 cm⁻¹ are particularly enhanced in the Q_y pre-resonance Raman spectra. Bands due to both the C₂O and C₉O stretches appear at 1700–1620 cm⁻¹, providing structural information on these carbonyl groups. In the CC stretching region (1620–1490 cm⁻¹), the correlation between band positions and the co-ordination number of central magnesium, which was previously found in the Soret-excited Raman spectra, is preserved in the Q_y, pre-resonance Raman spectra as well. The relative intensities of strong bands in the 1200–1000 cm⁻¹ region appear to be useful for characterizing the BChl state. By using these advantages of the Q_y, pre-resonance Raman spectra, molecular interactions and arrangements of BChl in hydrated films and in the B870 light-harvesting complex of R. sphaeroides are discussed.     

F.t.i.r. and Raman spectra of triphenylphosphine,triphenylarsine, triphenylstibine,and dibenzylsulphide

The f.t.i.r. and Raman spectra of triphenylphosphine, triphenylarsine, triphenylstibine, and dibenzylsulphide in the solid state at ca 80 K have been recorded over the ranges 3500-40 cm⁻¹ (infra-red, 1 cm⁻¹ resolution) and 1650-30 cm⁻¹ (Raman, 2 cm⁻¹ resolution). The data, particularly those in the low wavenumber region, are more extensive, more complete, and of higher quality than those obtained in previous studies. Detailed band assignments are given.     

Über Chalkogenolate. 85. Untersuchungen über Halbester der Trithiokohlensäure 3. Schwingungsspektren von Alkylthioxanthogensäuren und Wasserstoffbrücken in den freien Säuren

On Chalcogenolates. 85. Studies on Hemiesters of Trithiocarbonic Acid 3. Vibrational Spectra of Alkyl Thioxanthic Acids and Hydrogen Bondings in the Free Acids The IR spectra of alkyl thioxanthic acids RS? CS(SH) with R = CH₃, C₂H₅, ⁿC₃H₇, ⁱC₃H₇, ⁿC₄H₉, ^sC₄H₉, ^tC₄H₉, and CH₃S? CS(SD) as well as the Raman spectrum of the Compound with R = CH₃ have been assigned. The formation of hydrogen bondings in the free acids has been studied by means of i.r. spectra, ¹H-n.m.r. spectra, and electron absorption spectra. The energies of the hydrogen bondings have been calculated.     

Spectra and structure of phosphorus—boron compounds—XXVI. Infrared and Raman spectra,conformational stability and normal coordinate analysis of ethyldichlorophosphine-borane

The Raman (3500-10 cm⁻¹) and infrared (3500-50 cm⁻¹) spectra of solid ethyldichlorophosphine-borane, CH₃CH₂P(BH₃)Cl₂ and its deuterated analog, CH₃CH₂P(BD₃)Cl₂ have been recorded. Additionally, the infrared spectra of the gases and the Raman spectra of the liquids have been recorded and qualitative depolarization ratios have been obtained. Based on the fact that several distinct Raman lines disappear on going from the liquid to the solid state, it is concluded that the molecule exists as a mixture of the gauche and trans conformers, with the trans conformer being more stable in the liquid phase, and the only one present in the solid phase. From a temperature study of the Raman spectrum of the liquid, the enthalpy difference between the gauche and trans conformers was determined to be nearly zero. Based on Raman depolarization data, group frequencies, isotopic shift factors and infrared band contours, a complete vibrational assignment has been proposed for the trans conformer. The assignment is supported by a normal coordinate calculation which was carried out utilizing a modified valence force field to obtain the frequencies of the normal modes and the potential energy distribution. The BH₃ torsion has been observed at 188 cm⁻¹, while the BD₃ torsion was not observed. The methyl torsions in the spectra of the solids have been observed at 209 and 202 cm⁻¹ for the “light” and deuterated species, respectively. From the torsional data, barriers to internal rotation have been calculated. The asymmetric torsional mode has been observed for the trans conformer in the infrared spectra of the gas phase at 108 and 104 cm⁻¹ for the BH₃ and BD₃ species, respectively. These results are compared with similar quantities for some corresponding organophosphine—borane compounds.     

The vibrational and electronic spectroscopy of trifluorothioacetyl fluoride

The spectroscopy of trifluorothioacetyl fluoride (CF₃CSF), an unstable yellow gas, has been studied in the 50–5000 and 12 000–52 000 cm⁻¹ regions. From gas phase FT-i.r. and Raman spectra and i.r. absorption studies in an Ar matrix, the majority of the vibrational frequencies have been assigned. Three electronic transitions were identified in the u.v.-visible.     

A reassignment of the vibrational fundamentals of sulfuryl chloride fluoride

Low temperature Raman spectroscopy has led to a significant revision in the assignment of the vibrational fundamentals of sulfuryl chloride fluoride (SO₂FCl). The fundamentals in cm⁻¹ are: (a′) 1230, 826, 632, 503, 422, 295; (a″) 1469, 476, 303. All are from gas-phase i.r. spectra except 295 cm⁻¹, which is from the liquid-phase Raman spectrum. The revised assignments are consistent with the predictions of Pfeiffer's normal coordinate calculations [Z. phys. chem., Leipzig 240, 380 (1969)].