1. Ultrafast dynamics in the power stroke of a molecular rotary motor
- Author
-
Arjen Cnossen, Stephen R. Meech, Ben L. Feringa, Wesley R. Browne, Kiri Addison, Ismael A. Heisler, Jamie Conyard, Stratingh Institute of Chemistry, and Synthetic Organic Chemistry
- Subjects
Time Factors ,Light ,General Chemical Engineering ,EXCITED-STATE ,Molecular Dynamics Simulation ,ACCELERATION ,Spectrum Analysis, Raman ,010402 general chemistry ,Photochemistry ,01 natural sciences ,UNIDIRECTIONAL ROTATION ,TORSIONAL DYNAMICS ,Reaction coordinate ,Quantitative Biology::Subcellular Processes ,Molecular dynamics ,Isomerism ,PHOTOISOMERIZATION ,Molecular motor ,Absorption (electromagnetic radiation) ,Mechanical energy ,Fluorescent Dyes ,ISOMERIZATION ,Fluorenes ,010405 organic chemistry ,Chemistry ,FEMTOSECOND ,General Chemistry ,CIS-STILBENE ,0104 chemical sciences ,Coherent control ,Chemical physics ,Potential energy surface ,COHERENT-CONTROL ,STRUCTURAL MODIFICATION ,Excitation - Abstract
Light-driven molecular motors convert light into mechanical energy through excited-state reactions. Unidirectional rotary molecular motors based on chiral overcrowded alkenes operate through consecutive photochemical and thermal steps. The thermal (helix inverting) step has been optimized successfully through variations in molecular structure, but much less is known about the photochemical step, which provides power to the motor. Ultimately, controlling the efficiency of molecular motors requires a detailed picture of the molecular dynamics on the excited-state potential energy surface. Here, we characterize the primary events that follow photon absorption by a unidirectional molecular motor using ultrafast fluorescence up-conversion measurements with sub 50 fs time resolution. We observe an extraordinarily fast initial relaxation out of the Franck-Condon region that suggests a barrierless reaction coordinate. This fast molecular motion is shown to be accompanied by the excitation of coherent excited-state structural motion. The implications of these observations for manipulating motor efficiency are discussed.
- Published
- 2012