Aggregation-enhanced excimer emission (AEEE) based on pyrenylchalcone and 2-to-4 molecular decoder by biothiols and polyanions in aqueous media

Abstract

An aggregation-enhanced excimer emission (AEEE) fluorophore was successfully synthesized by introducing chalcone into pyrene. Compared with the traditional AIE structure (tetra-phenylethene derivatives), pyrenylchalcone was more available under mild conditions. It exhibited weak emission when molecularly dissolved but strong excimer emission when aggregated. Then we designed a probe with good water solubility based on pyrenylchalcone for polyanion detection in aqueous media. An orange emission could be observed upon simple addition of polyacrylic acid sodium salt. Better than the other “blue-to-green” pyrene probes, this “turn-on” AEEE probe was more likely visible to eyes. Moreover, unlike the double bond in tetra-phenylethene, the unsaturated double bond in chalcone could be easily opened by thiols. It could lead to another different “turn-on” change in fluorescence. Adding biothiol and adding polyanion were two different methods to reduce the intra-molecular rotations and cause different emissions, thus we built a 2-to-4 molecular decoder in aqueous media which could be observed by naked eyes.