Design and Investigation of Carbazole–Dithienylethene Compounds for Switchable Organic Radical Systems

Photoswitchable radicals incorporating dithienylethene (DTE) moieties offer unique opportunities for dynamic control in various chemical and material applications. By exploiting light-triggered isomerization processes, researchers can achieve precise modulation of radical reactivity, enabling spatiotemporal control of chemical transformations. Despite growing interest in this field, challenges remain in controlling spin–orbit coupling and spin dynamics, which influence the electronic structure and transitions induced by light absorption as well as achieving photostability for repeated photoisomerization cycles. To address these challenges, we have designed a new family of photoswitchable organic radicals that incorporate DTE moieties and carbazole radical centers. We studied the influence of spin delocalization through the molecular structure and spin evolution upon light irradiation by using ultraviolet/visible absorption, electron paramagnetic resonance, and nuclear magnetic resonance spectroscopies. Our findings demonstrate the photochromic behavior of the neutral form and reversible radical formation, contributing to advancements in this promising field.