Phenolic Deprotonation Triggered NIR-emission and Large Stokes Shift of BODIPY dyes

Abstract

BODIPY derivatives are well-known for their high brightness, especially, NIR emissive BODIPY derivatives with moderate to large Stokes shift were highly desired. Different from regular expanding the π-conjugation by fusing aromatic rings, in the current work, a spontaneous deprotonation strategy was developed by introducing one or two functional phenol groups onto the BODIPY core, by which a series of BODIPY derivatives with NIR emissions (up to λem = 791 nm) and significantly enlarged Stokes shifts (up to 223 nm) were synthesized. DFT computation results disclosed that the red-shifting of absorption and emission, as well as the enlargement of Stokes shift, are attributed to the deprotonation of phenolic hydroxyl group which not only prompts intramolecular charge transferring but also bends the plane structure of BODIPY cores. The resultant BODIPY showed significant photogenerated singlet oxygen capability and high photo penetration ability.