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Excited‐State Dynamic Planarization of Cyclic Oligothiophenes in the Vicinity of a Ring‐to‐Linear Excitonic Behavioral Turning Point
Author(s) -
Park Kyu Hyung,
Kim Pyosang,
Kim Woojae,
Shimizu Hideyuki,
Han Minwoo,
Sim Eunji,
Iyoda Masahiko,
Kim Dongho
Publication year - 2015
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201504588
Subject(s) - chemical mechanical planarization , delocalized electron , exciton , excited state , conjugated system , ring (chemistry) , chemical physics , ring size , materials science , fluorescence , molecular dynamics , molecular physics , chemistry , nanotechnology , photochemistry , computational chemistry , atomic physics , physics , condensed matter physics , optics , polymer , organic chemistry , layer (electronics) , composite material
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.