Exciton Localization in Extended {\pi}-electron Systems: Comparison of Linear and Cyclic Structures
Abstract
We employ five {\pi}-conjugated model materials of different molecular shape --- oligomers and cyclic structures --- to investigate the extent of exciton self-trapping and torsional motion of the molecular framework following optical excitation. Our studies combine steady-state and transient fluorescence spectroscopy in the ensemble with measurements of polarization anisotropy on single molecules, supported by Monte Carlo simulations. The dimer exhibits a significant spectral red-shift within 100 ps after photoexcitation which is attributed to torsional relaxation. This relaxation mechanism is inhibited in the structurally rigid macrocyclic analogue. However, both systems show a high degree of exciton localization but with very different consequences: while in the macrocycle the exciton localizes randomly on different parts of the ring, scrambling polarization memory, in the dimer, localization leads to a deterministic exciton position with luminescence characteristics of a dipole. Monte Carlo simulations allow us to quantify the structural difference between the emitting and absorbing units of the {\pi}-conjugated system in terms of disorder parameters.
Keywords
Cite
@article{arxiv.1506.05522,
title = {Exciton Localization in Extended {\pi}-electron Systems: Comparison of Linear and Cyclic Structures},
author = {Alexander Thiessen and Dominik Würsch and Stefan-S. Jester and A. Vikas Aggarwal and Alissa Idelson and Sebastian Bange and Jan Vogelsang and Sigurd Höger and John M. Lupton},
journal= {arXiv preprint arXiv:1506.05522},
year = {2015}
}