Publication

Ultrafast Excited State Dynamics in a First Generation Photomolecular Motor

Sardjan, A. S., Roy, P., Danowski, W., Bressan, G., Nunes dos Santos Comprido, L., Browne, W. R., Feringa, B. L. & Meech, S. R., Apr-2020, In : Chemphyschem. 21, 7, p. 594-599 7 p.

Research output: Contribution to journalArticleAcademicpeer-review

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.

Original languageEnglish
Pages (from-to) 594-599
Number of pages7
JournalChemphyschem
Volume21
Issue number7
Early online date23-Jan-2020
Publication statusPublished - Apr-2020

    Keywords

  • excited state, fluorescence, coherence, molecular motor, photochemistry, ultrafast dynamics, MOLECULAR MOTORS, UNIDIRECTIONAL ROTATION, VIBRATIONAL COHERENCE, PHOTOISOMERIZATION, ACCELERATION, SPEED

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