Radical-Formation Management: Towards Aza-Analogues of the Benzothioxanthene Imide

While benzothioxanthene imide (BTI) has shown promise in organic electronics and more recently in photodynamic therapy, its full potential remains yet undiscovered. In this context, this study repots the synthesis and characterization of aza derivatives in which the characteristic sulfur atom is replaced by an amino group. Adapted from the synthetic route of the BTI, a way was found to control the electronic structure of the radical intermediates, by means of a simple chemical modification. As a result, either the thermodynamically six-membered or the kinetically favored five-membered ring regioisomers can selectively be accessed. Photophysical rationalization of their structure-property relationships confirmed the richness, versatility and tunability of this class of rylene imide-based dyes.