Restriction of Conformation Transformation in Excited State: An Aggregation-Induced Emission Building Block Based on Stable Exocyclic C=N Group

Restriction of Conformation Transformation in Excited State: An Aggregation-Induced Emission Building Block Based on Stable Exocyclic C=N Group

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Summary: The development of aggregation-induced emission (AIE) building block and deciphering its luminescence mechanism are of great significance.Here a feasible strategy for the construction of hardware AIE unit based on E-Z isomerization (EZI) of exocyclic C=N double bond is proposed.Taking [1,2,4]thiadiazole[4,3-a]pyridine (TZP) derivative as an example, its aryl-substituted derivative (TZPP) shows obvious AIE character.

The analysis of spectral data and theoretical calculations indicates that fast structural relaxation of TZPP in the emissive state plays a key role in a low fluorescence quantum yield in dilute solution, which should be caused by the small energy gap between locally excited (LE) state and twisted U-matic Blank Video Tape intramolecular charge transfer state.When in solid state, the bright emission with LE state characteristic reappears due to the large shift barrier of geometry transformation.As a potential building block for AIEgens with special heterocyclic structure, these findings would open up opportunities for developing various functional materials.