TY - JOUR
T1 - Conformational information from vibrational spectra of styrene, trans-stilbene, and cis-stilbene
AU - Choi, Cheol Ho
AU - Kertesz, Miklos
PY - 1997/5/15
Y1 - 1997/5/15
N2 - Two electron correlation theories, second-order Møller-Plesset perturbation (MP2), and density functional (DFT) methods have been adopted to obtain fully optimized structures of styrene, trans-stilbene, and cis-stilbene. Full geometry optimizations with MP2 shows that the nonplanar conformations of styrene and trans-stilbene are preferred by 0.24 (styrene) and 0.80 kcal/mol (trans-stilbene), respectively. However, B3LYP, BLYP, and BVWN prefer a planar conformation contradicting the MP2 results. Due to the disorder of the crystal, X-ray experimental data of C=C double bond length of trans-stilbene seem to be too short. Vibrational spectra of these molecules are calculated at the BLYP/6-31++G** level without any empirical scaling. The agreement with experiment is excellent, some normal modes are reassigned. The dependence of the IR spectrum as a function of conformation in the 700-800 cm-1 region allows the determination of the solution-phase conformation. Both styrene and trans-stilbene are planar in solution, implying that these molecular conformations are mainly determined by the intermolecular forces rather than intramolecular ones.
AB - Two electron correlation theories, second-order Møller-Plesset perturbation (MP2), and density functional (DFT) methods have been adopted to obtain fully optimized structures of styrene, trans-stilbene, and cis-stilbene. Full geometry optimizations with MP2 shows that the nonplanar conformations of styrene and trans-stilbene are preferred by 0.24 (styrene) and 0.80 kcal/mol (trans-stilbene), respectively. However, B3LYP, BLYP, and BVWN prefer a planar conformation contradicting the MP2 results. Due to the disorder of the crystal, X-ray experimental data of C=C double bond length of trans-stilbene seem to be too short. Vibrational spectra of these molecules are calculated at the BLYP/6-31++G** level without any empirical scaling. The agreement with experiment is excellent, some normal modes are reassigned. The dependence of the IR spectrum as a function of conformation in the 700-800 cm-1 region allows the determination of the solution-phase conformation. Both styrene and trans-stilbene are planar in solution, implying that these molecular conformations are mainly determined by the intermolecular forces rather than intramolecular ones.
UR - http://www.scopus.com/inward/record.url?scp=0000947936&partnerID=8YFLogxK
U2 - 10.1021/jp970620v
DO - 10.1021/jp970620v
M3 - Article
AN - SCOPUS:0000947936
SN - 1089-5639
VL - 101
SP - 3823
EP - 3831
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 20
ER -