title: Acenaphthylene-fused cyclo[8]pyrroles with intense near-IR-region absorption bands.
abstract: An acenaphthylene-fused cyclo[8]pyrrole was synthesized by using an oxidative coupling reaction of the corresponding 2,2'-bipyrrole. Two conformational isomers 1 a and 1 b were isolated, and their molecular structures were elucidated by X-ray crystallographic studies. The less-polar and lower-symmetry 1 b isomer can be converted into the 1 a isomer through a thermal ring flip. Application of the perimeter model developed by Michl to magnetic circular dichroism spectroscopic data and theoretical calculations demonstrate that there is a marked redshift of the near-IR absorption maxima relative to cyclo[8]isoindole because there is a significant stabilization of the LUMO due to the differing effects of a fused ring expansion with acenaphthylene and benzene moieties on the frontier π molecular orbitals.
authors.affiliation: Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan), Fax: (+81) 89-927-9615. okujima.tetsuo.mu@ehime-u.ac.jp.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Okujima
authors.forename: Chie
authors.initials: C
authors.lastname: Ando
authors.forename: John
authors.initials: J
authors.lastname: Mack
authors.forename: Shigeki
authors.initials: S
authors.lastname: Mori
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisaki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nakae
authors.forename: Hiroko
authors.initials: H
authors.lastname: Yamada
authors.forename: Keishi
authors.initials: K
authors.lastname: Ohara
authors.forename: Nagao
authors.initials: N
authors.lastname: Kobayashi
authors.forename: Hidemitsu
authors.initials: H
authors.lastname: Uno
keywords: IR spectroscopy; circular dichroism; density functional calculations; macrocycles; pyrroles