Aggregation-induced emission, photochromism and self-assembly of pyrazolone phenlysemicarbazones

• Four pyrazolone phenylsemicarbazone derivatives exhibiting typical AIE behaviors.
• In the aggregating process, they can form 1D nanorods from 0D nanoballs.
• They have solid-state reversible photochromic properties.

Four pyrazolone phenylsemicarbazone derivatives, 1,3-diphenyl-4-(3-substituent)-5-hydroxypyrazole 4-phenylsemicarbazone [substituent = chlorolbenzal (1), fluorobenzal (2), bromobenzal (3) and benzal (4)], were synthesized. On the one hand, the four compounds exhibit good solid-state photochromic behaviors upon the irradiation of UV light and heat, and high fatigue resistance. On the other hand, they have aggregation-induced emission (AIE) characteristics. The emission could also be greatly enhanced by cooling solutions, suggesting that the aggregation-induced emission is caused by the restricted intramolecular rotations of the peripheral aromatic rings or other substituents around the central pyrazole ring. In addition, with the increase of the aging time, aggregates of these compounds can self-assemble into 1D nanostructures from 0D nanoballs by the reprecipitation, leading to the red-shift of emission spectra. Thus, it paves the way for preparing multifunctional materials with photochromic and AIE behaviors.

Four pyrazolone phenylsemicarbazone derivatives not only exhibit good reversible photochromic behaviors and high fatigue resistance in the solid state, but also have aggregation-induced emission characteristics and self-assembly behaviors in solution. Meanwhile, with the increase of the aging time, aggregates of these compounds can self-assembly into 1D nanostructures from 0D nanoballs by the reprecipitation.Figure optionsDownload as PowerPoint slide