Article Dans Une Revue ChemSystemsChem Année : 2019

The Motion of an Azobenzene Light‐Controlled Switch: A Joint Theoretical and Experimental Approach

Résumé

To gain further insight into the internal motion of molecular objects, we have synthesized a molecular turnstile AzoT composed of a rotor based on flexible tetraethyleneglycol (TEG) chains grafted on aromatic moieties and a stator containing a photoswitchable azobenzene (Azo) fragment. The control of the reversible light‐induced E‐AzoT⇆Z‐AzoT isomerization is supported by both NMR spectroscopy and photophysical investigation, which show that the system exhibits a fatigueless isomerization switching process. Furthermore, 2D NMR spectroscopy points to the fact that the free internal motion is triggered by the E‐AzoT⇆Z‐AzoT isomerization. Using molecular dynamics simulations and DFT calculations we have investigated the nature of the internal motions. An internal rotation characterized by an energy barrier of 23 kJ/mol is found for the Z‐AzoT isomer. In contrast, this barrier reaches 151 kJ/mol for the E‐AzoT isomer, excluding any “classical” rotation at room temperature. This rotational movement could in principle occur via tunneling. A simple model calculation, however, excludes tunnelling to take place before 20 ms.

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hal-03011738 , version 1 (18-11-2020)

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Bérangère Godde, Abdelaziz Jouaiti, Matteo Mauro, Roberto Marquardt, Alain Chaumont, et al.. The Motion of an Azobenzene Light‐Controlled Switch: A Joint Theoretical and Experimental Approach. ChemSystemsChem, 2019, 1 (3), pp.e1900003. ⟨10.1002/syst.201900003⟩. ⟨hal-03011738⟩
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