Cis-trans isomerisation of azobenzenes studied by laser-coupled NMR spectroscopy and DFT calculations.
In a combined experimental and computational study of a group of para-substituted azobenzenes, the effects of substituents and solvent on the kinetics of thermal cis-to-trans isomerisation have been examined and the success of DFT calculations in predicting kinetic parameters assessed. Mono-substituted species are predicted to isomerise by inversion in both non-polar and polar solvent, whereas for push-pull azobenzenes the mechanism is predicted to change from inversion to rotation on going from non-polar to polar solvent. Computed free energies of activation qualitatively reproduce experimental trends but do not quantitatively predict the kinetics of cis-trans isomerisation. The polarisable continuum model of solvation fails to predict the experimentally observed influence of solvent on the entropy of activation.
Wazzan
Nuha A
NA
School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, UKEH9 3JJ.
Richardson
Patricia R
PR
Jones
Anita C
AC