Chiral Boron Dipyrromethene Dye with Acid‐Responsive Near‐Infrared Emission and Chiral Optical Behavior

A chiral boron dipyrromethene (BODIPY) dye, denoted as (R)-2, incorporating near-infrared (NIR) emission and chiral optical behavior, is synthesized. The dye is engineered by coupling polyethylene glycol chains with R-stereogenic centers to a donor-acceptor BODIPY core through a Suzuki coupling reaction. This modification significantly enhances the solubility and facilitates efficient chirality transfer resulting in distinct circular dichroism (CD) activity, which is quite remarkable in organic small molecule solutions. Furthermore, acid-triggered protonation of the dye leads to a bathochromic shift in the maximum absorption wavelength (from 633 to 664 nm) and an increase in NIR emission intensity, which is attributed to the enhanced intramolecular charge transfer in solution.