Ultrafast motion in a third generation photomolecular motor

Area of Science:

• Photochemistry
• Molecular Machines
• Spectroscopy

Background:

• Controlling nanoscale molecular motion is crucial for developing synthetic molecular machines.
• Third-generation molecular motors (3GMs) utilize overcrowded alkenes for light-driven unidirectional rotation and translational motion.

Purpose of the Study:

• To investigate the excited state dynamics of 3GMs to understand their mechanism.
• To elucidate the reaction coordinate and factors influencing photoconversion efficiency.

Main Methods:

• Time-resolved absorption and emission spectroscopy to track population and coherence dynamics.
• Femtosecond stimulated Raman spectroscopy to reveal real-time structural dynamics.

Main Results:

• Detailed characterization of excited state evolution from Franck-Condon bright-state to metastable product.
• Identified charge transfer character in the dark-state, influenced by solvent polarity.
• Observed correlation between enhanced quantum yield and suppressed excited-state flapping motion.

Conclusions:

• Provides new insights into the reaction coordinate of 3GMs.
• Demonstrates that solvent polarity and substituent effects can modulate motor efficiency.
• Facilitates the rational design and development of more efficient molecular motors.