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- 저자 : rthner, Frank (검색결과 5 건)
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Son, Minjung,Fimmel, Benjamin,Dehm, Volker,Wü,rthner, Frank,Kim, Dongho WILEY‐VCH Verlag 2015 CHEMPHYSCHEM -WEINHEIM- Vol.16 No.8
<P>The excited-state photophysical behavior of a spiral perylene bisimide (PBI) folda-octamer (F8) tethered to an oligophenylene-ethynylene scaffold is comprehensively investigated. Solvent-dependent UV/Vis and fluorescence studies reveal that the degree of folding in this foldamer is extremely sensitive to the solvent, thus giving rise to an extended conformation in CHCl3 and a folded helical aggregate in methylcyclohexane (MCH). The exciton-deactivation dynamics are largely governed by the supramolecular structure of F8. Femtosecond transient absorption (TA) in the near-infrared region indicates a photoinduced electron-transfer process from the backbone to the PBI core in the extended conformation, whereas excitation power- and polarization-dependent TA measurements combined with computational modeling showed that excitation energy transfer between the unit PBI chromophores is the major deactivation pathway in the folded counterpart.</P>
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Perylene Bisimide Radicals and Biradicals: Synthesis and Molecular Properties
Schmidt, David,Son, Minjung,Lim, Jong Min,Lin, Mei‐,Jin,Krummenacher, Ivo,Braunschweig, Holger,Kim, Dongho,Wü,rthner, Frank WILEY‐VCH Verlag 2015 Angewandte Chemie. international edition Vol.54 No.47
<P><B>Abstract</B></P><P>Unprecedented neutral perylene‐3,4:9,10‐tetracarboxylic acid bisimide (PBI) radicals and biradicals were synthesized by facile chemical oxidation of 4‐hydroxyaryl‐substituted PBIs. Subsequent characterization by optical and magnetic spectroscopic techniques, as well as quantum chemical calculations, revealed an open‐shell singlet biradical ground state for the PBI biradical <B>OS</B>‐<B>2<SUP>..</SUP></B> (〈s<SUP>2</SUP>〉=1.2191) with a relatively small singlet–triplet energy gap of 0.041 eV and a large singlet biradical character of <I>y</I>=0.72.</P>
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Kaufmann, Christina,Kim, Woojae,Nowak-Kró,l, Agnieszka,Hong, Yongseok,Kim, Dongho,Wü,rthner, Frank American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.12
<P>An adequately designed, bay-tethered perylene bisimide (PBI) dimer <B>Bis-PBI</B> was synthesized by Pd/Cu-catalyzed Glaser-type oxidative homocoupling of the respective PBI building block. This newly synthesized PBI dimer self-assembles exclusively and with high binding constants of up to 10<SUP>6</SUP> M<SUP>-1</SUP> into a discrete π-stack of four chromophores. Steady-state absorption and emission spectra show the signatures of H-type excitonic coupling among the dye units. Broadband fluorescence upconversion spectroscopy (FLUPS) reveals an ultrafast dynamics in the optically excited state. An initially coherent Frenkel exciton state that is delocalized over the whole quadruple stack rapidly (τ = ∼200 fs) loses its coherence and relaxes into an excimer state. Comparison with Frenkel exciton dynamics in PBI dimeric and oligomeric H-aggregates demonstrates that in the quadruple stack coherent exciton propagation is absent due to its short length of aggregates, thereby it has only one relaxation pathway to the excimer state. Furthermore, the absence of pump-power dependence in transient absorption experiments suggests that multiexciton cannot be generated in the quadruple stack, which is in line with time-resolved fluorescence measurements.</P> [FIG OMISSION]</BR>
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Nowak-Kró,l, Agnieszka,Fimmel, Benjamin,Son, Minjung,Kim, Dongho,Wü,rthner, Frank The Royal Society of Chemistry 2015 Faraday discussions Vol.185 No.-
<P>Foldamer systems comprised of two perylene bisimide (PBI) dyes attached to the conjugated backbones of 1,2-bis(phenylethynyl)benzene and phenylethynyl-bis(phenylene)indane, respectively, were synthesized and investigated with regard to their solvent-dependent properties. UV/Vis absorption and steady-state fluorescence spectra show that both foldamers exist predominantly in a folded H-aggregated state consisting of π–π-stacked PBIs in THF and in more random conformations with weaker excitonic coupling between the PBIs in chloroform. Time-resolved fluorescence spectroscopy and transient absorption spectroscopy reveal entirely different relaxation pathways for the photoexcited molecules in the given solvents, <I>i.e.</I> photoinduced electron transfer leading to charge separated states for the open conformations (in chloroform) and relaxation into excimer states with red-shifted emission for the stacked conformations (in THF). Supported by redox data from cyclic voltammetry and Rehm–Weller analysis we could relate the processes occurring in these solution-phase model systems to the elementary processes in organic solar cells. Accordingly, only if relaxation pathways such as excimer formation are strictly avoided in molecular semiconductor materials, excitons may diffuse over larger distances to the heterojunction interface and produce photocurrent <I>via</I> the formation of electron/hole pairs by photoinduced electron transfer.</P>
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Lee, Ji-Eun,Stepanenko, Vladimir,Yang, Jaesung,Yoo, Hyejin,Schlosser, Felix,Bellinger, Daniel,Engels, Bernd,Scheblykin, Ivan G.,Wü,rthner, Frank,Kim, Dongho American Chemical Society 2013 ACS NANO Vol.7 No.6
<P>Properties of a series of acetylene-linked perylene bisimide (PBI) macrocycles with different ring size composed of three to six PBI dyes were investigated by atomic force microscopy (AFM) and single-molecule fluorescence spectroscopy in a condensed phase. It was demonstrated that the structures of PBI cyclic arrays (C<I>N</I>s, <I>N</I> = 3, 4, 5, and 6) become distorted with increasing the ring size through molecular dynamics (MD) simulations (PM6-DH2 method) and AFM height images of C<I>N</I>s on highly ordered pyrolytic graphite (HOPG) surface. The MD simulations showed that only <B>C5</B> and <B>C6</B> rings are highly flexible molecules whose planarization goes along with a significant energetic penalty. Accordingly, both molecules did not show ordered adlayers on a HOPG surface. In contrast, <B>C3</B> and <B>C4</B> are far more rigid molecules leading to well-ordered hexagonal (<B>C3</B>) and rectangular (<B>C4</B>) 2D lattices. At the single-molecule level, we showed that the fluorescence properties of single C<I>N</I>s are affected by the structural changes. The fluorescence lifetimes of C<I>N</I>s became shorter and their distributions became broader due to the structural distortions with increasing the ring size. Furthermore, the C<I>N</I>s of smaller ring size exhibit a higher photostability and an efficient excitation energy transfer (EET) due to the more well-defined and planar structures compared to the larger C<I>N</I>s. Consequently, these observations provide evidence that not only PBI macrocycles are promising candidates for artificial light-harvesting systems, but also the photophysical properties of C<I>N</I>s are strongly related to the structural rigidity of C<I>N</I>s.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-6/nn400616u/production/images/medium/nn-2013-00616u_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn400616u'>ACS Electronic Supporting Info</A></P>
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