2, 6‐Bis(arylsulfonyl)anilines as Fluorescent Scaffolds through Intramolecular Hydrogen Bonds: Solid‐State Fluorescence Materials and Turn‐On‐Type Probes Based on Aggregation‐Induced Emission. Issue 4 (31st January 2014) - Beppu, Teruo
Abstract A series of 2, 6‐bis[aryl(alkyl)sulfonyl]anilines were synthesized by nucleophilic aromatic substitution of 2, 6‐dichloronitrobenzene with various aryl or alkyl thiolates (benzyl‐, phenyl‐, 2‐naphthyl‐, and 2‐aminophenyl thiolate), followed by hydrogenation and subsequent oxidation. All prepared 2, 6‐bis[aryl‐(alkyl)sulfonyl]anilines showed high fluorescence emissions in the solid state; X‐ray structures revealed well‐defined intramolecular hydrogen bonds, which served to immobilize the rotatable amino group and generate a fluorescence enhancement in addition to improved photostability. Moreover, absorption and fluorescence spectra showed redshifts in the order of benzyl<phenyl<2‐naphthyl in solution and the solid state, and DFT calculations confirmed charge transfer from the central aniline unit to the side aryl groups through the sulfonyl bridges, which together indicated the push–pull effect with an extended π‐conjugated system comprising the 2, 6‐bis(arylsulfonyl)aniline unit. Furthermore, 2, 6‐bis(2‐aminophenylsulfonyl)aniline, with rotatable amino groups at the flanking aryl units, was affected by fluorescence quenching in solution. This nonemissive state showed an enhanced environmental sensitivity to solvent polarity and viscosity, along with a "turn‐on" fluorescence response in frozen solvent and in the aggregated form. 2, 6‐Bis(2‐aminophenylsulfonyl)aniline behaved as a turn‐on fluorescence probe for selective detection of DNA based on its aggregation‐induced emission.