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Published on: October 31, 2019
Attraction or Repulsion? London Dispersion Forces Control Azobenzene Switches
Luca Schweighauser1, Marcel A Strauss1, Silvia Bellotto1
1Institut für Organische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Gießen (Germany).
Abstract:
Large substituents are commonly seen as entirely repulsive through steric hindrance. Such groups have additional attractive effects arising from weak London dispersion forces between the neutral atoms. Steric interactions are recognized to have a strong influence on isomerization processes, such as in azobenzene-based molecular switches. Textbooks indicate that steric hindrance destabilizes the Z isomers. Herein, we demonstrate that increasing the bulkiness of electronically equal substituents in the meta-position decreases the thermal reaction rates from the Z to the E isomers. DFT computations revealed that attractive dispersion forces essentially lower the energy of the Z isomers.
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