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Near‐Infrared Circularly Polarized Luminescence through Intramolecular Excimer Formation of Oligo( p ‐phenyleneethynylene)‐Based Double Helicates
Author(s) -
Miki Koji,
Noda Takeru,
Gon Masayuki,
Tanaka Kazuo,
Chujo Yoshiki,
Mizuhata Yoshiyuki,
Tokitoh Norihiro,
Ohe Kouichi
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201901467
Subject(s) - luminescence , intramolecular force , excimer , infrared , chemistry , materials science , photochemistry , stereochemistry , optoelectronics , optics , physics , fluorescence
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 ( Φ PL =0.93). In contrast, flexible binaphthyl units induced dynamic structural change of the oligo( p ‐phenyleneethynylene) luminophores under photoirradiation, leading to strong CPL (| g lum |=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.