Driving Triplet State Population in Benzothioxanthene Imide Dyes: Let's twist!

Abstract

Controlling the formation of photoexcited triplet states is critical for many (photo)chemical and physical applications. Here, we demonstrate that a permanent out‐of‐plane distortion of the benzothioxanthene imide (BTI) dye promotes intersystem crossing by increasing spin‐orbit coupling. This manipulation was achieved through a subtle chemical modification, specifically the bay‐area methylation. Consequently, this simple yet efficient approach expands the catalog of known molecular engineering strategies for synthesizing heavy atom‐free, dual redox‐active, yet still emissive and synthetically accessible photosensitizers.