Low-Frequency Vibrations of Molecular Solids. X. CH3CCl3, CD3CCl3, CH3CCl2H, and CH3CF3

Abstract

The far-infrared spectra of solid CHaCCIa and CDaCCla have been investigated from 33 to 400 cm-l . Raman spectra of these solids have also been recorded. The internal torsional mode was observed at 290 and 206 cml in the infrared spectra of solid methylchloroform and methylchloroform-da, respectively. The threefold periodic barrier to rotation was calculated to be 5.5 kcal/mol. This barrier is compared to those previously reported by other techniques for this molecule and the reported value is much larger than that currently accepted. Four lattice vibrations, 46.9, 53.4, 57.7, and 67.5 cml were observed in the far-infrared spectrum of methylchloroform recorded at -190°C. Both the effect of temperature variation and deuterium substitution were investigated for these bands. These lattice modes shifted to lower frequency and became quite diffuse as the temperature approached the phase transition at -68°C. The low-frequency Raman spectrum of methylchloroform at -165°C showed one line at 38.6 cm-1 which shifted to 37.0 cml with deuteration. The infrared spectra of solid CHaCHCb and CHaCFa have been recorded between 140 and 400 cm-l . The internal torsional mode for 1, I-dichloroethane was observed at 232 and 231 cml for the solid and vapor, respectively. The threefold barrier to rotation was calculated to be 3.50 kcal/mol. The internal torsion for methylfluoroform was observed at 220 cm-l for the solid, and the barrier was calculated to be 3.29 kcal/mol. Substituent effects on the barrier heights are discussed.

Rotational spectrum, structure and internal rotation in CH3CCl3

“…To complicate the situation, relative intensity measurements in the microwave spectrum gave a barrier, V 3 = 1.74 (30) kcal mol À1 [9] in good agreement with the thermodynamic determination. Furthermore, the torsional frequency obtained from the neutron scattering study value was confirmed by a Raman study in solid phase which gives m s = 290 cm À1 [10]. This last result prompted a new microwave study and, from the relative intensities of the rotational transitions in ground and excited vibrational states, the frequency of the torsional mode was found to be 276(10) cm À1 [11].…”

Strong Coriolis coupling between and states of studied by millimeter-wave spectroscopy

“…This argument, when combined with relative intensity considerations, made it possible to assign new bands to the next higher unassigned excited vibrational states in 35 Cl 3 CCH 3 , namely second lowest A-symmetry mode, m 5 and the second lowest E-symmetry mode, m 11 . Ab initio calculations and the available information on the infrared spectrum [14] indicated that the wavenumbers for these modes are both in the 350 cm À1 region. There is still a problem in that it was unlikely that the bands X 1 ; X 2 reflected interstate interactions completely since the progressions of lines away from the bandheads were in both bands in the same direction.…”

Magnetization Dynamics on Isotope‐Isomorphic Holmium Single‐Molecule Magnets

“…[1][2][3][4][5][6][7][8][9][10][11] Thanks to the considerable mass difference, for example ca. 100 % mass increase from protium ( 1 H) to deuterium ( 2 H or D) and the different nuclear spin as well, the isotope effect is more pronounced in further affecting the associated inter/intramolecular behavior, like the strength of hydrogen bond, [12][13][14] the lattice vibration/ spin-phonon coupling, [15][16][17][18][19] and the much smaller gyromagnetic ratio of the deuterium spin ( 2 H: 1 H = 1:6.5). As a weakly interacted monodisperse system, single-molecule magnets (SMMs) exhibit slow magnetic relaxation arising from their large magnetic anisotropy, which shows the ability of magnetic memory at the single-molecule level.…”