High-temperature vapor-phase Raman spectra and assignment of the low-frequency modes of trans-stilbene and 4-methoxy-trans-stilbene
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abstract
The vapor-phase Raman spectra of trans-stilbene at 330C and 4-methoxy-trans-stilbene at 350C have been recorded using a specially constructed high temperature cell. Together with the dispersed fluorescence spectra, these spectra have been used to assign the eight low-frequency vibrational modes in each molecule. For trans-stilbene, strong polarized bands at 273 and 152 cm-1 were ascribed to the totally symmetric v24 (Ce-phenyl bend) and v25 (in-plane phenyl wag), respectively. A depolarized band at 207 cm-1 was assigned to the Bg phenyl flap (v47), and a polarized shoulder near 125 cm-1 is believed to result from both the Bg phenyl torsion (v48) and the overtone of the Au phenyl flap (v36). For 4-methoxy-trans-stilbene the Ce-phenyl bend and in-plane phenyl wag were shifted to 234 and 144 cm-1, respectively. These assignments were critical for understanding the fluorescence spectra associated with the torsional motions. 1996 Elsevier Science B.V. All rights reserved.
