TY - JOUR
T1 - Internal rotation of methyl group in 2- and 1-methylanthracene studied by electronic spectroscopy and DFT calculations
AU - Nakagaki, Masayuki
AU - Nishi, Eriko
AU - Sakota, Kenji
AU - Nishi, Kaori
AU - Nakano, Haruyuki
AU - Sekiya, Hiroshi
N1 - Funding Information:
The authors wish to thank Prof. H. Nakai and Mr. M. Kawai (Waseda University) for valuable discussion. This work was supported in part by the Grant-in-Aid for Scientific Research No. 15250015 from the Japanese Ministry of Education, Science, Sports and Culture.
PY - 2005/9/19
Y1 - 2005/9/19
N2 - The S1-S0 fluorescence excitation and dispersed fluorescence spectra of 2- and 1-methylanthracene are measured in a supersonic free jet expansion. The barrier heights to internal rotation in the S 0 and S1 states of 2-methylanthracene are determined to be 69 and 335 cm-1, respectively, by using a one-dimensional free-rotor model. A prominent 0-0 transition has been observed in the fluorescence excitation spectrum of 1-methylanthracene, but no methyl rotational bands have been detected in both the excitation and dispersed fluorescence spectra. The potential energy curves of the methyl rotation are obtained for 2- and 1-methylanthracene with density functional theory (DFT) calculations and time-dependent (TD)-DFT calculations at the B3LYP/6-31 + G(d,p) level. The barrier heights and the phase of the potential energy curve are very different between 2- and 1-methylanthracene and substantially depend on the electronic state. These differences are consistently explained by a π*-σ * hyperconjugation effect introduced by Nakai and Kawai [Chem. Phys. Lett. 307 (1999) 272].
AB - The S1-S0 fluorescence excitation and dispersed fluorescence spectra of 2- and 1-methylanthracene are measured in a supersonic free jet expansion. The barrier heights to internal rotation in the S 0 and S1 states of 2-methylanthracene are determined to be 69 and 335 cm-1, respectively, by using a one-dimensional free-rotor model. A prominent 0-0 transition has been observed in the fluorescence excitation spectrum of 1-methylanthracene, but no methyl rotational bands have been detected in both the excitation and dispersed fluorescence spectra. The potential energy curves of the methyl rotation are obtained for 2- and 1-methylanthracene with density functional theory (DFT) calculations and time-dependent (TD)-DFT calculations at the B3LYP/6-31 + G(d,p) level. The barrier heights and the phase of the potential energy curve are very different between 2- and 1-methylanthracene and substantially depend on the electronic state. These differences are consistently explained by a π*-σ * hyperconjugation effect introduced by Nakai and Kawai [Chem. Phys. Lett. 307 (1999) 272].
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U2 - 10.1016/j.chemphys.2005.06.006
DO - 10.1016/j.chemphys.2005.06.006
M3 - Article
AN - SCOPUS:24344434027
VL - 316
SP - 178
EP - 184
JO - Chemical Physics
JF - Chemical Physics
SN - 0301-0104
IS - 1-3
ER -