Aggregation-Induced Orange-to-Red Fluorescence of 2,5-Bis(diarylamino)terephthalic Acid Dithioesters

-conjugated systems substituted by electron donors (D) or acceptors (A) are useful platforms for various kinds of organic optoelectronic materials. The exploration and development of new donors and acceptors can expand the possible molecular designs of D--A-type electronic structures. Herein we report 2,5-bis(diarylamino)terephthalic acid dithioesters, in which organosulfanylcarbonyl groups serve as electron acceptors, as new fluorophores exhibiting efficient solid-state emission. The absorption spectra of the thioesters in toluene show two bands, with the smaller band located at the longer wavelength corresponding to the intramolecular charge-transfer transition from the diarylamino to organosulfanylcarbonyl groups. The dithioesters are faintly fluorescent in toluene, but exhibit efficient orange-to-red emission in the powder form; therefore, aggregation-induced emission was observed. Compared with the corresponding terephthalic acid diesters, the fluorescence spectra of the dithioesters in the powder form are significantly redshifted.