J. Phys. Chem. A 2003, 107, 8659-8664
8659
Quantum Chemical Studies on Photoinduced Cis-Trans Isomerization and Intramolecular Hydrogen Atom Transfer of 2′-Hydroxychalcone Yasuo Norikane,‡ Naofumi Nakayama,§ Nobuyuki Tamaoki,‡ Tatsuo Arai,| and Umpei Nagashima*,⊥ Institute for Materials and Chemical Process, National Institute of AdVanced Industrial Science and Technology (AIST), Central 5, 1-1-1, Higashi, Tsukuba, Ibaraki, 305-8565, Japan, Best Systems Inc., 2-1-6 Sengen, Tsukuba, Ibaraki 305-0047, Japan, Department of Chemistry, UniVersity of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan, and Grid Technology Research Center, National Institute of AdVanced Industrial Science and Technology (AIST), Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568, Japan ReceiVed: December 25, 2002; In Final Form: March 7, 2003
The reaction mechanism of the one-way isomerization of 2′-hydroxychalcone (2HC) was studied by calculating the potential energy surfaces of the twist of the CdC double bond and the intramolecular hydrogen atom transfer in the excited triplet state by the UB3LYP/6-31G** level. The calculations reveal the following. The potential energy curve of the triplet state between the keto forms (trans-2HC and cis-2HC) is similar to that of stilbene, which exhibits mutual isomerization. On the other hand, the potential energy curve between the enol forms (trans-2HC′ and cis-2HC′) is similar to that of styrylanthracene, which exhibits one-way isomerization from the cis to trans isomer. Although the hydrogen atom transfer has an energy barrier (
