Molecular Distortion of trans-Stilbene and the Raman Intensity of the In-Phase CH Out-of-Plane Wag of the Central CHCH Group

Abstract

A long-standing issue, i.e., whether the molecule of trans-stilbene is distorted around the central CC bond and/or the C−phenyl bond in solution, is examined by performing density functional calculations of the Raman intensity of the in-phase CH out-of-plane wag of the central CHCH group. Dependencies of the Raman intensity of the said mode upon the torsional angles around the central CC and C−phenyl bonds are calculated. Not only the normal species of trans-stilbene but also two isotope-labeled species, C6H513CH13CHC6H5 and C6H5CDCDC6H5, are treated. Comparisons of the calculated results with the observed spectra show that the trans-stilbene molecule is distorted in solution. The ranges of distortion around the central CC and C−phenyl bonds are estimated to be 2.5−4.0° and 8.0−12.0°, respectively, from the planar arrangement around the respective bonds.