Sardjan, Andy S., Roy, Palas, Danowski, Wojciech, Bressan, Giovanni, Nunes dos Santos Comprido, Laura, Browne, Wesley R., Feringa, Ben L. and Meech, Stephen R. (2020) Ultrafast Excited State Dynamics in a First Generation Photomolecular Motor. ChemPhysChem, 21 (7). pp. 594-599. ISSN 1439-4235

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Abstract

Efficient photomolecular motors will be critical elements in the design and development of molecular machines. Optimisation of the quantum yield for photoisomerisation requires a detailed understanding of molecular dynamics in the excited electronic state. Here we probe the primary photophysical processes in the archetypal first generation photomolecular motor, with sub-50 fs time resolved fluorescence spectroscopy. A bimodal relaxation is observed with a 100 fs relaxation of the Franck-Condon state to populate a red-shifted state with a reduced transition moment, which then undergoes multi-exponential decay on a picosecond timescale. Oscillations due to the excitation of vibrational coherences in the S 1 state are seen to survive the ultrafast structural relaxation. The picosecond relaxation reveals a strong solvent friction effect which is thus ascribed to torsion about the C−C axle. This behaviour is contrasted with second generation photomolecular motors; the principal differences are explained by the existence of a barrier on the excited state surface in the case of the first-generation motors which is absent in the second generation. These results will help to provide a basis for designing more efficient molecular motors in the future.

Item Type:	Article
Uncontrolled Keywords:	acceleration,molecular motors,photoisomerization,speed,unidirectional rotation,vibrational coherence,coherence,excited state,fluorescence,molecular motor,photochemistry,ultrafast dynamics
Faculty \ School:	Faculty of Science > School of Chemistry
Related URLs:	http://www.scopus.com/inward/record.url?... https://onlinelibrary.wiley.com/doi/abs/...
Depositing User:	LivePure Connector
Date Deposited:	21 Jan 2020 10:48
Last Modified:	03 Apr 2020 00:45
URI:	https://ueaeprints.uea.ac.uk/id/eprint/73709
DOI:	10.1002/cphc.201901179

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