Substrate induced catalysis: Deciphering the weak acid triggered bleaching of an angular terthiazole photochromic dye

摘要

The thermal bleaching of the ring-closed colored isomer of a photochromic triangle terthiazole induced by a weak acid in acetonitrile was investigated from a kinetic point of view. A realistic model was proposed involving not less than nine species and thirteen elementary processes. Our studies highlight the importance of the transient monoprotonated species in the carbon-carbon bond weakening and confirm the role of the proton as catalyst for the ring opening. The origin of the sigmoid shape of the Absorbance vs time traces is discussed.