Thermochromism and photochromism of aryl-substituted acyclic azines II: Photokinetics

Abstract

Acyclic azines with higher condensed aromatic and heterocyclic substituents are photochromic and show both thermal isomerization and photochemical isomerization. From the point of view of formal kinetics the azines can be divided into four reaction types depending on the substituents R i . The correspondence of the expected formal kinetic behaviour of the azines with the experimental results is a direct proof of a photochemical E– Z isomerization of these compounds. We investigated acyclic azines which fulfil all criteria of a complicated unitary photoreaction of the type A ⇌ B as well as those azines showing a reversible consecutive photoreaction A ⇌ B ⇌ C. All quantum yields were determined using formal kinetics.