Photomodulation of the proton affinity and acid gated photochromism of a novel dimethylaminophenyl thiazole diarylethene

The acid-gated photochromism and the photomodulation of fluorescence and proton affinity of a novel dimethylaminophenyl thiazole diarylethene in MeCN were investigated from a kinetic point of view. Photomodulation of the proton affinities has been estimated from acid titrations and numerical modelling of the acid induced T-photochromism. The basicities of the thiazole and dimethylamino protonation sites are different by only one pK unit. Upon ring- closure, their relative proton affinities are reversed. Our investigations underline the role of the thiazole protonation in the carbon-carbon bond weakening of the closed form and validate the role of the proton as catalyst in the gated T-photochromism. (C) 2011 Elsevier Ltd. All rights reserved.