Chromophoric cyclic polyenes including 4H-pyrans

fulvenes

and siloles are designed and synthesized.Unlike "conventional" luminescent molecules

these polyenes are practically nonemissive when molecularly dissolved

but become highly luminescent with a dramatic increase in emission efficiency when aggregated(hence "aggregation-induced emission" or AIE).Upon exposure to solvent vapors

their emissions on TLC plates are quenched but become visible again when the vapors are removed.This process is reversible and can be repeated many times.Their emissions can also be tuned by changing their packing patterns such as from crystalline to amorphous state or from one crystal form to another crystal form.