Journal article

An artificial molecular switch that mimics the visual pigment and completes its photocycle in picoseconds

Single mols. that act as light-energy transducers (e.g., converting the energy of a photon into at.-level mech. motion) are examples of minimal mol. devices. Here, we focus on a mol. switch designed by merging a conformationally locked diarylidene skeleton with a retinal-like Schiff base and capable of mimicking, in soln., different aspects of the transduction of the visual pigment Rhodopsin. Complementary ab initio multiconfigurational quantum chem.-based computations and time-resolved spectroscopy are used to follow the light-induced isomerization of the switch in methanol. The results show that, similar to rhodopsin, the isomerization occurs on a 0.3-ps time scale and is followed by <10-ps cooling and solvation. The entire (2-photon-powered) switch cycle was traced by following the evolution of its IR spectrum. These measurements indicate that a full cycle can be completed within 20 ps.


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