title: Benzoannelated aza-, oxa- and azaoxa[8]circulenes as promising blue organic emitters.
abstract: In the present work, we studied the synergetic effect of benzoannelation and NH/O-substitution for enhancing the absorption intensity in a series of novel designed benzoannelated aza- and oxa[8]circulenes. Semi-empirical estimations of the fluorescence rate constants allowed us to determine the most promising fluorophores among all the possible benzoannelated aza-, oxa- and mixed azaoza[8]circulenes. Among them, para-dibenzoannelated [8]circulenes demonstrated the most intense light absorption and emission due to the prevailing role of the linear acene chromophore. Calculated φflvalues are in complete agreement with experimental data for a number of already synthesized circulenes. Thus, we believe that the most promising circulenes designed in this study can demonstrate an intensive fluorescence in the case of their successful synthesis, which in turn could be extremely useful for the fabrication of future blue OLEDs. Special attention is devoted to the aromaticity features and peculiarities of the absorption spectra for the two highly-symmetrical (D4hground state symmetry) π-isoelectronic species as well as the so-called tetrabenzotetraaza[8]circulene and tetrabenzotetraoxa[8]circulene molecules. Both of them are characterized by rich electronic spectra, which can be assigned only by taking into account the vibronic coarse structure of the first electronic absorption band; the 0-1 and 0-2 transitions were found to be active in the absorption spectrum in complete agreement with experimental data obtained for both energy and intensity. The corresponding promotive vibrational modes have been determined and their vibronic activity estimated using the Franck-Condon approximation.
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, 10691 Stockholm, Sweden. glibar@kth.se and Department of Chemistry and Nanomaterials Science, Bogdan Khmelnitsky National University, Cherkasy, 18031, Ukraine.
authors.forename: Gleb V
authors.initials: GV
authors.lastname: Baryshnikov
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, 10691 Stockholm, Sweden. glibar@kth.se and Tomsk State University, 36 Lenin Avenue, Tomsk, Russia and Tomsk Polytechnic University, 43a Lenin Avenue, Tomsk, Russia.
authors.forename: Rashid R
authors.initials: RR
authors.lastname: Valiev
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, 10691 Stockholm, Sweden. glibar@kth.se.
authors.forename: Nataliya N
authors.initials: NN
authors.lastname: Karaush
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, 10691 Stockholm, Sweden. glibar@kth.se.
authors.forename: Valentina A
authors.initials: VA
authors.lastname: Minaeva
authors.affiliation: Tomsk State University, 36 Lenin Avenue, Tomsk, Russia.
authors.forename: Alexandr N
authors.initials: AN
authors.lastname: Sinelnikov
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Stephan K
authors.initials: SK
authors.lastname: Pedersen
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Pittelkow
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, 10691 Stockholm, Sweden. glibar@kth.se and Department of Chemistry and Nanomaterials Science, Bogdan Khmelnitsky National University, Cherkasy, 18031, Ukraine.
authors.forename: Boris F
authors.initials: BF
authors.lastname: Minaev
authors.affiliation: Division of Theoretical Chemistry and Biology, School of Biotechnology, KTH Royal Institute of Technology, 10691 Stockholm, Sweden. glibar@kth.se.
authors.forename: Hans
authors.initials: H
authors.lastname: Ågren