title: Radical ions of cyclopyrenylene: comparison of spectral properties with cycloparaphenylene.
abstract: Hoop-shaped π-conjugated molecules have attracted much attention. In this study, the radical ions of [4]cyclo-2,7-pyrenylene ([4]CPY), a cyclic tetramer of pyrene, and [4]cyclo-4,5,9,10-tetrahydro-2,7-pyrenylene ([4]CHPY) were investigated using radiation chemical methods, namely, γ-ray radiolysis and pulse radiolysis. The absorption spectra of the radical ions of [4]CPY and [4]CHPY showed clear peaks in the near-IR and UV-vis regions similar to those of [8]cycloparaphenylene ([8]CPP). Theoretical calculations using time-dependent density functional theory provided reasonable assignments of the observed absorption bands. It was indicated that the C4-C5 and C9-C10 ethylene bonds of [4]CHPY do not contribute to the electronic transitions, resulting in absorption spectra similar to those of [8]CPP. On the other hand, it was confirmed that the allowed electronic transitions of the radical ions of [4]CPY are different from those of the radical ions of [4]CHPY and [8]CPP.
authors: †The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors: Mamoru
authors: M
authors: Fujitsuka
authors: †The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors: Sachiko
authors: S
authors: Tojo
authors: ‡Institute for Chemical Research, Kyoto University, Uji 611-0011, Japan.
authors: Takahiro
authors: T
authors: Iwamoto
authors: ‡Institute for Chemical Research, Kyoto University, Uji 611-0011, Japan.|§CREST, Japan Science and Technology Agency, Tokyo 102-0076, Japan.
authors: Eiichi
authors: E
authors: Kayahara
authors: ‡Institute for Chemical Research, Kyoto University, Uji 611-0011, Japan.|§CREST, Japan Science and Technology Agency, Tokyo 102-0076, Japan.
authors: Shigeru
authors: S
authors: Yamago
authors: †The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors: Tetsuro
authors: T
authors: Majima