Fluorescence Spectra and Torsional Potential Energy Functions for 4-Methoxy-trans-stilbene in its S0 and S1(.pi.,.pi.) Electronic States Academic Article uri icon

abstract

  • The fluorescence excitation spectra and dispersed fluorescence spectra of 4-methoxy-frans-stilbene have been recorded and analyzed. Assignments were made for all eight of the low-frequency vibrational modes, excluding the methoxy and methyl torsions, for the S0ground state and for five of the low-frequency vibrations in the S1(π,π*) electronic excited state. Numerous transitions involving the two-phenyl torsions and the C=C torsion were observed. These were utilized to determine the two-dimensional vibrational energy surface for the phenyl torsions and to evaluate the one-dimensional ethylenic torsion for both the S0and S1states. For the phenyl torsions the barriers to simultaneous internal rotation were calculated to be 2860 cm-1for both the So and S1states, about 200 cm-1lower than the trans-stilbene values. The C=C torsional barrier for the S0state was estimated to be 52 ± 3 kcal/mol based on its observed overtone frequency at 172 cm-1. For the excited state the C=C torsional overtone series can be observed beginning at 171 cm-1. Analysis of the potential function for this mode indicates that the barrier to trans-twist interconversion is approximately 245 cm-1higher than that for trans-stilbene. © 1995 American Chemical Society.

author list (cited authors)

  • Chiang, W., & Laane, J.

citation count

  • 13

publication date

  • August 1995