Circularly Polarized Light Probes Excited-State Delocalization in Rectangular Ladder-type Pentaphenyl Helices

Robin Ammenhäuser, Patrick Klein, Eva Schmid, Sabrina Streicher, Jan Vogelsang, Christian W. Lehmann, John M. Lupton, Stefan C.J. Meskers (Corresponding author), Ullrich Scherf

Research output: Contribution to journalArticleAcademicpeer-review

8 Citations (Scopus)
51 Downloads (Pure)

Abstract

Ladder-type pentaphenyl chromophores have a rigid, planar π-system and show bright fluorescence featuring pronounced vibrational structure. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report the synthesis of helical polymers with a rigid square structure based on spiro-linked ladder-type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit through breakdown of the Born-Oppenheimer approximation. The dynamic conversion between delocalized and localized excited states provides a new paradigm for interpreting circular dichroism in helical polymers such as proteins and polynucleic acids.

Original languageEnglish
Article numbere202211946
Number of pages8
JournalAngewandte Chemie - International Edition
Volume62
Issue number2
DOIs
Publication statusPublished - 9 Jan 2023

Keywords

  • Chirality
  • Circular Dichroism
  • Circular Polarization of Luminescence
  • Helical Ladder Polymers
  • Spiro Bisfluorene Linkers
  • Vibration
  • Polymers/chemistry

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