Kinetic study of the fast thermal cis-to-trans isomerisation of para-, ortho- and polyhydroxyazobenzenes

Jaume Garcia-Amorós, Antoni Sánchez-Ferrer, Walter A. Massad, Santi Nonell, Dolores Velasco
2010 Physical Chemistry, Chemical Physics - PCCP  
The thermal cis-to-trans isomerisation process has been studied for a series of para-, ortho-and polyhydroxy-substituted azobenzenes in different solvents. The kinetics of the thermal back reaction for the p-hydroxy-substituted azobenzenes depend strongly on the nature of the solvent used, with relaxation times ranging from 200-300 milliseconds in ethanol to half an hour in toluene. Otherwise, the process rate is mainly independent of the solvent nature for the ortho substituted analogues.
more » ... ydroxy-substituted azobenzenes show very much faster kinetics than the para-and ortho-monohydroxyazoderivatives. With relaxation times of 6-12 milliseconds in ethanol, they are optimal molecules for designing fast optical switching devices. All the hydroxyazoderivatives thermally isomerise from the metastable cis form to the thermodynamically stable trans isomer through a rotational mechanism.
doi:10.1039/c004340k pmid:20820477 fatcat:7a6rtc4mtfaw5e6yjxhvypegxy