A New Deep‐Red to Near‐infrared Emission and Polarity Sensitive Fluorescent Probe Based on β‐Diketone‐boron Difluoride and Coumarin Derivative

Abstract A new polarity sensitive fluorescent probe CO ‐ DBD with deep‐red to near‐infrared emission was designed and synthesized. CO ‐ DBD consists of β‐diketone‐boron difluoride and coumarin moieties, showing higher fluorescence intensity and shorter emission wavelength in low‐polarity solvent. Notably, CO ‐ DBD gives high absolute fluorescence quantum yield of 0.631 in toluene. Theoretical calculation results verify that the polarity response is attributed to intramolecular charge transfer and twisted intramolecular charge transfer process. Further experimental data demonstrate that CO ‐ DBD displays high selectivity, sensitivity and excellent stability. The precise polarity of binary mixture can be quantified by ratio fluorescence intensity of CO ‐ DBD . Moreover, this probe is successfully applied for live cell imaging with high contrast.