Switching a pH indicator by a reversible photoacid: A quantitative analysis of a new two-component photochromic system

The coupling between a simple water soluble spiropyran reversible photoacid and a pH indicator has been quantitatively analysed. The initial pH, stoichiometric ratio, light intensity and pKa range have been determined to maximize the proton transfer from the photochromic donor to the pH-indicator acceptor.224