Excited-state dynamic planarization of cyclic oligothiophenes in the vicinity of a ring-to-linear excitonic behavioral turning point

Kyu Hyung Park, Pyosang Kim, Woojae Kim, Hideyuki Shimizu, Minwoo Han, Eunji Sim*, Masahiko Iyoda, Dongho Kim

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Excited-state dynamic planarization processes play a crucial role in determining exciton size in cyclic systems, as reported for π-conjugated linear oligomers. Herein, we report time-resolved fluorescence spectra and molecular dynamics simulations of π-conjugated cyclic oligothiophenes in which the number of subunits was chosen to show the size-dependent dynamic planarization in the vicinity of a ring-to-linear behavioral turning point. Analyses on the evolution of the total fluorescence intensity and the ratio between 0-1 to 0-0 vibronic bands suggest that excitons formed in a cyclic oligothiophene composed of six subunits fully delocalize over the cyclic carbon backbone, whereas those formed in larger systems fail to achieve complete delocalization. With the aid of molecular dynamics simulations, it is shown that distorted structures unfavorable for efficient exciton delocalization are more easily populated as the size of the cyclic system increases. Going around in circles: Excited-state dynamic planarization processes of π-conjugated cyclic oligothiophenes were investigated using time-resolved fluorescence spectra and molecular dynamics simulations. Excitons formed in a cyclic oligothiophene composed of six subunits fully delocalize ("cyclic exciton"), whereas those formed in larger systems fail to achieve complete delocalization ("acyclic exciton").

Original languageEnglish (US)
Pages (from-to)12711-12715
Number of pages5
JournalAngewandte Chemie - International Edition
Volume54
Issue number43
DOIs
StatePublished - Oct 1 2015

Keywords

  • conformation analysis
  • conjugation
  • excitons
  • oligothiophenes
  • photophysics

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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