We combine time-resolved spectroscopic studies, on time scales ranging from femtoseconds to seconds, with density functional theory (DFT) calculations to elucidate and apply the acidochromism of our recently designed iminothioindoxyl (ITI) photoswitch.
Protonation of ITI shifts its absorption to the orange/red part of the spectrum and allows for manipulation of the thermal half-life of the photogenerated E-isomer over three orders of magnitude.