Ultrafast electronic energy transfer beyond the weak coupling limit in a proximal but orthogonal molecular dyad

Hedley, G. J. , Ruseckas, A., Benniston, A. C., Harriman, A. and Samuel, I. D.W. (2015) Ultrafast electronic energy transfer beyond the weak coupling limit in a proximal but orthogonal molecular dyad. Journal of Physical Chemistry A, 119(51), pp. 12665-12671. (doi: 10.1021/acs.jpca.5b08640) (PMID:26617059)

Abstract

Electronic energy transfer (EET) from a donor to an acceptor is an important mechanism that controls the light harvesting efficiency in a wide variety of systems, including artificial and natural photosynthesis and contemporary photovoltaic technologies. The detailed mechanism of EET at short distances or large angles between the donor and acceptor is poorly understood. Here the influence of the orientation between the donor and acceptor on EET is explored using a molecule with two nearly perpendicular chromophores. Very fast EET with a time constant of 120 fs is observed, which is at least 40 times faster than the time predicted by Coulombic coupling calculations. Depolarization of the emission signal indicates that the transition dipole rotates through ca. 64°, indicating the near orthogonal nature of the EET event. The rate of EET is found to be similar to structural relaxation rates in the photoexcited oligothiophene donor alone, which suggests that this initial relaxation brings the dyad to a conical intersection where the excitation jumps to the acceptor.

• Item Type: Articles
• Additional Information: This work was funded by EPSRC Grants EP/G04094X/1 and EP/K50340X/1 (to AH) and EP/J009016/1 (to IDWS, GJH and AR) and from the European Union Seventh Framework Programme under grant agreement 321305 (IDWS).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Hedley, Dr Gordon
• Authors: Hedley, G. J., Ruseckas, A., Benniston, A. C., Harriman, A., and Samuel, I. D.W.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Physical Chemistry A
• Publisher: American Chemical Society
• ISSN: 1089-5639
• ISSN (Online): 1520-5215
• Copyright Holders: Copyright © 2015 American Chemical Society
• First Published: First published in Journal of Physical Chemistry A 119:12665-12671
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher