Reaction and excited state relaxation dynamics of photochromic dithienylethene derivatives

The spectroscopic properties as well as the reaction and relaxation dynamics of photochromic dithienylethene derivatives have been characterized. An in-depth understanding of these photochemical electrocyclic reactions, involving large conformational changes, is required for the optimization of the performance of these compounds as optical switches in photonic applications. Substituents. more or less strongly coupled to the electronic structure of dithienylethene unit were introduced. A threshold of the reactivity as a function of excitation energy has been established and the rate of the barrier-less ring closure reaction could be related to the spectral and steric properties of the substituent. The interplay of photochromism and fluorescence was characterized by attaching anthracene. The blue fluorescence of the open isomer is strongly suppressed in the closed isomer. (C) 2001 Elsevier Science B.V, All rights reserved.