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

Research output: Indexed journal article Articlepeer-review

99 Citations (Scopus)


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. Polyhydroxy-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.

Original languageEnglish
Pages (from-to)13238-13242
Number of pages5
JournalPhysical Chemistry Chemical Physics
Issue number40
Publication statusPublished - 2010


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