title: Synthesis and properties of highly fluorescent indolizino[3,4,5-ab]isoindoles.
abstract: We report here the synthesis, X-ray structures, optical and electrochemical properties, fabrication of light-emitting devices, and density functional calculations for indolizino[3,4,5-ab]isoindole (INI) derivatives. Strongly luminescent heterocycles based on the INI unit were synthesized by 1,3-dipolar cycloaddition reactions between pyrido[2,1-a]isoindole (PIS) and acetylene or ethylene derivatives. They are indolizino[3,4,5-ab]isoindoles 2-9 and 14-15, benzo[1',2'-1,2]indolizino[3,4,5-ab]isoindoles 10, pyridazino[4',5':1,2]indolizino[3,4,5-ab]isoindoles 12-13, and 2,3-hydropyridazino[4',5':1,2]indolizino[3,4,5-ab]isoindole-1,4-dione 11. The relative luminescence quantum yield can be as high as 90%. Their reduction and oxidation potentials and high luminescence can make these heterocycles possible alternatives to tris(8-hydroxyquinolinato)aluminum (Alq(3)). The brightness of the light-emitting device reached as high as 10(4) cd/m(2) and indolizino[3,4,5-ab]isoindole 3 emits beautifully blue light. The X-ray crystal structures of INI derivatives were obtained for the first time. The geometries obtained from X-ray data and density functional theory calculations shed more light on an interesting formally antiaromatic 16pi system, which is divided into 10pi and 6pi aromatic systems. We also report a relatively easy protonation of INI, which occurs at a carbon, rather than nitrogen atom.
authors.affiliation: Department of Chemistry and Biochemistry, Exotic Materials Institute, University of California-Los Angeles, Los Angeles, CA 90095-1569, USA.
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Mitsumori
authors.forename: Michael
authors.initials: M
authors.lastname: Bendikov
authors.forename: Olivier
authors.initials: O
authors.lastname: Dautel
authors.forename: Fred
authors.initials: F
authors.lastname: Wudl
authors.forename: Takeshi
authors.initials: T
authors.lastname: Shioya
authors.forename: Hideki
authors.initials: H
authors.lastname: Sato
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Sato