The Malleable Excited States of Benzothiadiazole Dyes and Investigation of their Potential for Photochemical Control

A new design strategy to control the efficiency of a photocleavage reaction based on changing the nature of the excited state is presented. A novel class of photoactive compounds has been synthesized by combining the classicalo-nitrobenzyl scaffold with an environmentally sensitive dye, 4-amino-nitrobenzothiazole. Irradiation in a polar solvent led to an excited state that was inoperative for photochemistry whereas excitation in a nonpolar solvent led to an excited state that was photochemically active. While our design hypothesis tests true for the on/off control of a photochemical process, an alternative photochemical ring-opening of the heterocycle appears to be the preferred process in contrast to the intended photocleavage process.