Logic Gating of Photochemical States Utilizing Nitroxide‐Free Radicals

Utilizing a fused isoindoline nitroxide-styrylpyrene system (StyPyNO), this work presents an interrogation into the effects of the radical spin on the [2+2] photocycloaddition of styrlpyrene and explores the photoswitchability of the system. Through irradiation with both broadband lamps and laser light sources, the influence of the nitroxide moiety on photoreactivity was analyzed and compared with both styryl pyrene and diamagnetic controls. The presence of the radical spin prevented the intermolecular [2+2] photocycloaddition observed from the control systems, instead allowing for a trans–cis photoisomerism under identical 420 nm irradiation conditions. Studies into the triplet lifetimes of the radical containing and control systems allowed for deeper understanding around the mechanism of photoreactivity. The system explored presents a means of controlling photo reaction progression not only via wavelength of irradiation, but also via the presence or removal of the unpaired electron within the nitroxide moiety. This in turn presents the potential for a dual gated chemical/photoswitchable system.