Aggregation-induced emissions of pyran, fulvene and silole derivatives

Novel π-conjugated molecules of 4H-pyran (1), fulvene (2), and silole (3) derivatives are designed and synthesized. Unlike conventional luminescent molecules, 1-3 are virtually nonluminescent in dilute solutions but become highly emissive with a dramatic boost in the luminescence efficiency upon aggregate formation (hence "aggregation- induced emission" or AIE). Their emissions on the TLC plates are quenched upon exposure to solvent vapors but become visibly emissive again when the solvents are removed. This process is reversible and can be repeated many times. The AIE processes of 1 and 2 are believed to be caused by intermolecular interaction, while that of 3 might be due to restriction of its molecular motions. Interesting fluorescence vapochromism is observed for a thin film of 3.