Radical cation of 1,3-butadiene: Resonance Raman spectrum of deuterated derivatives and improved force field

TitleRadical cation of 1,3-butadiene: Resonance Raman spectrum of deuterated derivatives and improved force field
Publication TypeJournal Article
Year of Publication1996
AuthorsKeszthelyi, T, Wilbrandt, R, Bailey, CA, Roulin, JL
JournalJournal of Physical Chemistry
Volume100
Pagination16850–16855
Date Publishedoct
Abstract

The resonance Raman spectra of the radical cations of three deuterated derivatives of 1,3-butadiene are reported. Together with the data for the parent compound (cf.: Keszthelyi, T.; Wilbrandt, R.; Bally, T. J. Phys. Chem. 1996, 100, 16843), 22 frequencies of totally symmetric fundamentals are available to complement 29 previously obtained IR data for the same compounds (Tang, W; Zhang, X.-L., Bally, T. J. Phys. Chem. 1993, 97, 4373) and to generate a new and improved scaled quantum mechanical force field of butadiene radical cation based on B3LYP/6-31G* second derivatives. After fitting those with 13 scaling factors, the resulting force field reproduces all 51 observed fundamental vibrations of the four isotopomers with a root-mean-square deviation of 6.03 cm(-1) (10.6 cm(-1) for the 11 strongly anharmonic C-H/C-D stretches, 3.92 cm(-1) for the remaining 40 modes). It allows the first experimentally based prediction of the stretching force constant for the central C-C bond and corrects the previous ones for the terminal C=C stretch. As in the case of the parent compound. evidence is presented for the presence of the s-cis rotamer after ionization whose vibrations are predicted very accurately by scaling a B3LYP/6-31G* force field of cis-butadiene(.+) with the optimized scaling factors of the s-trans rotamer.

URLhttp://dx.doi.org/10.1021/jp961839x
DOI10.1021/jp961839x