title: Multi-input/multi-output molecular response system based on the dynamic redox behavior of 3,3,4,4-tetraaryldihydro[5]helicene derivatives: reversible formation/destruction of chiral fluorophore and modulation of chiroptical properties by solvent polarity.
abstract: 3,3,4,4-Tetaaryldihydro[5]helicenes (1) and 1,1'-binaphthyl-2,2'-diylbis(diarylcarbenium)s (2(2+)) can be reversibly interconverted upon electron transfer, which is accompanied by a vivid color change (electrochromism) as well as by the formation/cleavage of a C-C bond ("dynamic redox behavior"). Because only the neutral donor 1 exhibits strong fluorescence, electrochemical input can further modify the fluorescent properties of the pair. Due to the configurational stability of the helicity in 1 and axial chirality in 2(2+), the redox reaction of optically pure material proceeds stereospecifically, which induces a chiroptical change such as circular dichroism (CD) as an additional output. The CD spectra of dications 2(2+) exhibit solvent dependency (chiro-solvatochromism), which is accompanied by solvatochromic behavior based on the pi-pi interaction of the two cationic chromophores as well as coordinative interaction of the Lewis basic solvent to the Lewis acidic triarylcarbenium moieties. Thus, the present system is endowed with multi-input functionality for modifying multiple output signals.
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: Yusuke
authors.initials: Y
authors.lastname: Ishigaki
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Iwai
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Kawai
authors.forename: Kenshu
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ikeda
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kano
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Mizuno