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Attraction or Repulsion? London Dispersion Forces Control Azobenzene Switches
Author(s) -
Schweighauser Luca,
Strauss Marcel A.,
Bellotto Silvia,
Wegner Hermann A.
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201506126
Subject(s) - steric effects , azobenzene , isomerization , attraction , dispersion (optics) , chemistry , london dispersion force , chemical physics , computational chemistry , stereochemistry , van der waals force , molecule , physics , catalysis , organic chemistry , optics , linguistics , philosophy
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.