Excited state structure correlates with efficient photoconversion in unidirectional motors

Roy, Palas, Sardjan, Andy S., Cnossen, Arjen, Browne, Wesley R., Feringa, Ben L. and Meech, Stephen R. ORCID: https://orcid.org/0000-0001-5561-2782 (2021) Excited state structure correlates with efficient photoconversion in unidirectional motors. The Journal of Physical Chemistry Letters, 12 (13). pp. 3367-3372. ISSN 1948-7185

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The design of unidirectional photomolecular motors demands a critical understanding of an ultrafast photochemical isomerization. An intermediate dark excited state mediates the reaction via a conical intersection (CI) with the ground state, but a correlation between molecular structure and photoisomerization efficiency has remained elusive. Here femtosecond stimulated Raman spectroscopy captures vibrational spectra of the dark state in a set of molecular motors bearing different substituents. A direct correlation between isomerization quantum yield, dark state lifetime, and excited state vibrational spectrum is found. Electron withdrawing substituents lead to activity in lower frequency modes, which we correlate with a pyramidalization distortion at the ethylenic axle occurring within 100 fs. This structure is not formed with an electron donating substituent, where the axle retains double bond character. Further structural reorganization is observed and assigned to excited state reorganization and charge redistribution on the sub-picosecond time scale. The correlation of the dark state structure with photoconversion performance suggests guidelines for developing new more efficient motor derivatives.

Item Type: Article
Additional Information: Funding Information: Financial support was provided by The Netherlands Ministry of Education, Culture and Science (Gravity Program 024.001.035 to W.R.B., B.L.F.) and the EPSRC (Grants EP/R042357/1, EP/J009148/1 to S.R.M.). We would like to thank Katrin Adamczyk for advise on FSRS alignment.
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Chemistry of Light and Energy
Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
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Depositing User: LivePure Connector
Date Deposited: 16 Apr 2021 23:57
Last Modified: 08 Mar 2024 11:31
URI: https://ueaeprints.uea.ac.uk/id/eprint/79799
DOI: 10.1021/acs.jpclett.1c00710


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