Near-Infrared Circularly Polarized Luminescence through Intramolecular Excimer Formation of Oligo(p-phenyleneethynylene)-Based Double Helicates |
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Authors: | Prof. Dr. Koji Miki Takeru Noda Prof. Dr. Masayuki Gon Prof. Dr. Kazuo Tanaka Prof. Dr. Yoshiki Chujo Prof. Dr. Yoshiyuki Mizuhata Prof. Dr. Norihiro Tokitoh Prof. Dr. Kouichi Ohe |
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Affiliation: | 1. Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615–8510 Japan;2. Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto, 615-8510 Japan;3. Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 Japan |
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Abstract: | Carbon-based double helicates consisting of two anthracene-containing oligo(p-phenyleneethynylene) units and two flexible chiral 1,1′-binaphthyl units or two rigid chiral 9,9′-spirobifluorene units were developed. The curved oligo(p-phenyleneethynylene) fragments in the double helicates were successfully constructed by tin-mediated reductive aromatization. Helical oligo(p-phenyleneethynylene) double strands fixed by two rigid spirobifluorene units showed little structural change under photoirradiation, thereby emitting circularly polarized luminescence (CPL) in the visible region with a high quantum yield (ΦPL=0.93). In contrast, flexible binaphthyl units induced dynamic structural change of the oligo(p-phenyleneethynylene) luminophores under photoirradiation, leading to strong CPL (|glum|=1.1×10−2) in the near-infrared (NIR) region. UV/Vis, circular dichroism (CD), CPL and NMR spectroscopic analyses of the binaphthyl-hinged double helicate suggested excimer formation between two π-conjugated strands in the excited state. Theoretical calculations highlight the importance of the tightly interlocked excimer structure of the carbon-based double helicate in controlling the angle between the electric and magnetic transition dipole moments for strong NIR CPL generation. |
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Keywords: | chirality circularly polarized luminescence excimer helical structures macrocycles |
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