title: 7,7,8,8-Tetraaryl-o-quinodimethane stabilized by dibenzo annulation: a helical π-electron system that exhibits electrochromic and unique chiroptical properties.
abstract: When two benzene rings are fused to a tetraaryl-o-quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermodynamic stability. Because the tetraarylbutadiene subunit contains electron-donating alkoxy groups, 1 undergo reversible two-electron oxidation to 2(2+), which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e.g., sec-butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2 b(2+) and 2 c(2+), which represents an efficient method for enhancing circular-dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X-ray analysis of dication 2(2+) revealed π-π stacking interaction of the diarylmethylium moieties, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, 060-0810, Japan. tak@sci.hokudai.ac.jp
authors.forename: Takanori
authors.initials: T
authors.lastname: Suzuki
authors.forename: Yuto
authors.initials: Y
authors.lastname: Sakano
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Iwai
authors.forename: Shinichi
authors.initials: S
authors.lastname: Iwashita
authors.forename: Youhei
authors.initials: Y
authors.lastname: Miura
authors.forename: Ryo
authors.initials: R
authors.lastname: Katoono
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Kawai
authors.forename: Kenshu
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Tsuji
authors.forename: Takanori
authors.initials: T
authors.lastname: Fukushima