Self-Sensitized Fulgimides with Selective Multiplicity-Based Three-State Photoswitching

Precise control over excited-state multiplicity is a powerful strategy for controlling photochemical reactivity, particularly in multimodal systems where different multiplicities lead to distinct reaction products. Here, we present a multiplicity-sensitive, multimodal, fulgimide-based system capable of three-state photoswitching both in solution and in the solid state. With the aim of suppressing singlet-state sensitization, we rationally designed an intramolecularly sensitized system that enables triplet-exclusive energy transfer-a crucial feature for selective multiplicity-dependent reactivity. Our findings provide insights into the underlying principles of intramolecular triplet-exclusive sensitization and its application in controlling three-state photoswitching in unimolecular systems.