Departmental Bulletin Paper シクロデキストリン共存下におけるピセンの2光子イオン化

竹下, 達哉  ,  Takeshita, Tatsuya  ,  久保, 葉月  ,  Kubo, Hazuki  ,  箕﨑, 知香  ,  Minosaki, Chika  ,  矢野, 篤  ,  Yano, Atsushi  ,  原, 道寛  ,  Hara, Michihiro

(47)  , pp.145 - 152 , 2017-07-11
Two-photon ionization (TPI) of picene (Pi) in the presence of cyclodextrin (CD) was investigated by using 266-nm laser pulse excitation. TPI of Pi was compared with TPI of phenanthrene (PH) and chrysene (Ch) from view point of the number of benzene rings. The formation of incorporation complex of Pi with CD (Pi/CD) was confirmed by 1H NMR measurement. The transient absorption of hydrated electrons released by Pi/CD was observed at 720 nm after a 5 ns laser flash at 266 nm. The ionization quantum yield (Φion) of Pi in the presence of α-, β-, and γ-CD (1.0 × 10-2 M) was calculated to be 3.4 ± 0.1%, 1.9 ± 0.1%, and 1.7 ± 0.1%, respectively, and it was attributed to the stabilization energy arising from solvation, which was affected by the area of Pi protruding from the cavity of the CD. When the concentration of CD was lowered to 1.0 × 10-3 M, Φion of Pi was increased by the stabilization energy arising from solvation. Additionally, we found that Φion of Pi with five benzene rings was much higher than PH and Ch with three and four benzene rings, respectively, which is because its structure is relatively susceptible to the stabilization of solvation. Overall, we concluded that the stabilization energy of solvation is important for the TPI of Pi/CD.

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