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Ultrafast Excited State Dynamics in a First Generation Photomolecular Motor
- Source :
- Chemphyschem, 21(7), 594-599. WILEY-V C H VERLAG GMBH, Chemphyschem
- Publication Year :
- 2020
- Publisher :
- Wiley, 2020.
-
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 S1 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.<br />Generation conflict? The excited state dynamics of first‐generation molecular motors are studied by means of ultrafast time resolved fluorescence. A 100 fs structural reorganization in the excited state is followed by a slower excited state relaxation, which is influenced by solvent viscosity. The decay is accompanied by coherent vibrational excitation of modes in the excited electronic state. The observed behaviour is contrasted with that of the second‐generation motors.
- Subjects :
- Transition dipole moment
MOLECULAR MOTORS
02 engineering and technology
Physics, Atomic, Molecular & Chemical
ACCELERATION
010402 general chemistry
01 natural sciences
Article
UNIDIRECTIONAL ROTATION
VIBRATIONAL COHERENCE
PHOTOISOMERIZATION
excited state
Molecular motor
0307 Theoretical and Computational Chemistry
SPEED
Physical and Theoretical Chemistry
0306 Physical Chemistry (incl. Structural)
Physics
Science & Technology
Chemical Physics
photochemistry
Chemistry, Physical
Articles
021001 nanoscience & nanotechnology
Atomic and Molecular Physics, and Optics
Molecular machine
coherence
0104 chemical sciences
molecular motor
Chemistry
ultrafast dynamics
Picosecond
Excited state
Physical Sciences
0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
fluorescence
Time-resolved spectroscopy
Atomic physics
0210 nano-technology
Ultrashort pulse
Excitation
Subjects
Details
- ISSN :
- 14397641 and 14394235
- Volume :
- 21
- Database :
- OpenAIRE
- Journal :
- ChemPhysChem
- Accession number :
- edsair.doi.dedup.....00426fb8cfba1f0f9521236df82631fa
- Full Text :
- https://doi.org/10.1002/cphc.201901179