Interactive Twin Intramolecular Hydrogen Bonds Enable Bright, S‐Blue Emissive, Environment‐Insensitive Single‐Benzene Fluorophores

Abstract Small‐molecule dyes that emit blue fluorescence, particularly those that emit in the S‐blue region, are limited in number. Functionalization of benzene with electron‐donating and ‐accepting groups generates single‐benzene fluorophores (SBFs) with tunable emission properties. By exploring the unprecedented, interactive twin intramolecular H‐bonds, a novel type of SBFs that exhibits several notable features for bioimaging applications is developed. Specifically, aniline derivatives bearing two carbonyl/carboxyl groups at ortho‐positions have interactive H‐bonds, which lead to conformational restriction, suppressed solvation, and increased HOMO‐LUMO energy gaps from those of the conventional SBFs that have non‐interactive H‐bonds. The interactive H‐bonds are manifested by notable photophysical properties among the new SBFs, such as S‐blue emissive, bright, photo‐ and chemo‐stable, solid‐state‐emissive, and environment (pH, polarity, and viscosity)‐insensitive. The use of the highly faceted dye system to develop a reliable fluorescent probe, organelle‐staining dyes, and a fluorescence‐resonance‐energy‐transfer probe for hydrogen sulfide demonstrates its potential in bioimaging applications.