A vibrational spectroscopic investigation of solid 1,3,5-cycloheptatriene

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Abstract
The vibrational spectra (infrared and Raman) of 1,3,5-cycloheptatriene have been obtained as functions of temperature. The bands in the spectra were broad and showed no splitting over the entire temperature range investigated, 47 to 235 K, indicating that solid 1,3,5-cycloheptatriene is disordered down to 47 K. Except for some differences in linewidth, there was little change in the spectra at the phase transition at 154 K. Unusual behaviour was observed in the spectra of both phases in that the vibrational bands were found to broaden with decreasing temperature. The low-frequency Raman spectrum at 47 K contained two broad bands, which is characteristic of a glassy crystal. A broad band was observed in the spectrum of the high-temperature phase, indicating that anisotropic reorientation was occurring on the experimental time scale.