title: Wurster's Blue-type cation radicals framed in a 5,10-dihydrobenzo[a]indolo[2,3-c]carbazole (BIC) skeleton: dual electrochromism with drastic changes in UV/Vis/NIR and fluorescence.
abstract: Electron-donating dihydrobenzindolocarbazoles (BICs) 1 a-c, which adopt planar disk-shaped geometries, were prepared by gold(I)-catalyzed cyclization as a key step. Due to the presence of a 1,4-phenylenediamine (PD) moiety in the framework, they undergo reversible one-electron oxidation to the corresponding Wurster's Blue (WB)-type species that exhibits NIR absorptions up to λ=1200 nm. In the case of the N,N'-dimethyl derivative, cation radical 1 c(+.) is stable enough to be isolated as a salt and X-ray analysis indicated paraquinoid-type bond alternation in the WB core unit, whereas the bond lengths in the peripheral benzene rings are identical to those in the neutral donor. Upon electrochemical interconversion, the redox pairs of 1 a-c and 1 a-c(+.) exhibited an electrochromic response in the UV/Vis/NIR region, which was accompanied by a drastic change in the fluorescence spectrum because only neutral donors 1 a-c are highly emissive (Φ(F) : 0.7-0.8).
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810 (Japan), Fax: (+81) 11-706-2714. 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: Yusuke
authors.initials: Y
authors.lastname: Tokimizu
authors.forename: Youhei
authors.initials: Y
authors.lastname: Miura
authors.forename: Ryo
authors.initials: R
authors.lastname: Katoono
authors.forename: Kenshu
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Naoki
authors.initials: N
authors.lastname: Yoshioka
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Fujii
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ohno
mesh_terms: D002412:Cations / Q000737:chemistry; D060326:Chemistry Techniques, Synthetic; D005453:Fluorescence; D015394:Molecular Structure; D009588:Nitrogen Mustard Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D019265:Spectroscopy, Near-Infrared; D013329:Structure-Activity Relationship; D013772:Tetramethylphenylenediamine / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D002412:Cations; D009588:Nitrogen Mustard Compounds; C100119:imidazole mustard; D013772:Tetramethylphenylenediamine
keywords: fluorescence; gold; heterocycles; molecular response system; redox chemistry