title: Kinetic study of the fast thermal cis-to-trans isomerisation of para-, ortho- and polyhydroxyazobenzenes.
abstract: 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.
authors.affiliation: Grup de Materials Orgànics, Institut de Nanociència i Nanotecnologia, Departament de Química Orgànica, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, E-08028, Barcelona, Spain.
authors.forename: Jaume
authors.initials: J
authors.lastname: Garcia-Amorós
authors.forename: Antoni
authors.initials: A
authors.lastname: Sánchez-Ferrer
authors.forename: Walter A
authors.initials: WA
authors.lastname: Massad
authors.forename: Santi
authors.initials: S
authors.lastname: Nonell
authors.forename: Dolores
authors.initials: D
authors.lastname: Velasco