Dynamic Evolution Processes Between Excited Triplet and Doublet States in Organic Photo-Responsive Materials

Organic photo-responsive materials, especially those involving excited multiple states (i.e., T₁ and D₁), have garnered significant attention for their wide potential applications. However, this class of materials, which partially originates from the unclear evolution processes between excited triplet and doublet states, is still relatively rare. Herein, we successfully developed a new photo-responsive system with coexisting photochromic and room-temperature phosphorescence properties in one molecule through optimizing the π-conjugation structure and molecular symmetry of triarylamine derivatives, and clearly uncovered the synergistic regulation mechanism of triplet exciton evolution and radical generation through femtosecond transient absorption (fs-TA) spectroscopy. Specifically, the evolution process of "S₁→T₁→D₁" was monitored, providing an efficient way to develop multifunctional photo-responsive materials involving both triplet and doublet states.