Direct Observation of a Dark State in the Photocycle of a Light-Driven Molecular Motor.
Controlling the excited-state properties of light driven molecular machines is crucial to achieving high efficiency and directed functionality. A key challenge in achieving control lies in unravelling the complex photodynamics and especially in identifying the role played by dark states. Here we use the structure sensitivity and high time resolution of UV-pump/IR-probe spectroscopy to build a detailed and comprehensive model of the structural evolution of light driven molecular rotors. The photodynamics of these chiral overcrowded alkene derivatives are determined by two close-lying excited electronic states. The potential energy landscape of these "bright" and "dark" states gives rise to a broad excited-state electronic absorption band over the entire mid-IR range that is probed for the first time and modeled by quantum mechanical calculations. The transient IR vibrational fingerprints observed in our studies allow for an unambiguous identification of the identity of the "dark" electronic excited state from which the photon's energy is converted into motion, and thereby pave the way for tuning the quantum yield of future molecular rotors based on this structural motif.
Physikalisches Institut, Westfälische Wilhelms-Universität Münster , Wilhelm-Klemm-Strasse 10, 48149 Münster, Germany.|Center for Nanotechnology , Heisenbergstrasse 11, 48149 Münster, Germany.|Molecular Photonics Group, Van 't Hoff Institute for Molecular Science, University of Amsterdam , Science Park 904, 1098XH Amsterdam, The Netherlands.
Saeed
S
Amirjalayer
Stratingh Institute for Chemistry and Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Arjen
A
Cnossen
Stratingh Institute for Chemistry and Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Wesley R
WR
Browne
Stratingh Institute for Chemistry and Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Ben L
BL
Feringa
Molecular Photonics Group, Van 't Hoff Institute for Molecular Science, University of Amsterdam , Science Park 904, 1098XH Amsterdam, The Netherlands.
Wybren J
WJ
Buma
Molecular Photonics Group, Van 't Hoff Institute for Molecular Science, University of Amsterdam , Science Park 904, 1098XH Amsterdam, The Netherlands.
Sander
S
Woutersen
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