Intramolecular Charge Transfer-Based Conjugated Oligomer with Fluorescence, Efficient Photodynamics, and Photothermal Activities.

To develop efficient photoactive agents with satisfactory fluorescence, photodynamic, and photothermal effects is crucial for a phototherapeutic strategy to combat cancer diseases and pathogenic microbes. Herein, a water-soluble donor-acceptor-donor (D-A-D) structured conjugated oligomer was designed and synthesized, consisting of two cyclopenta-dithiophene (CDT) units as the electron donor and boron dipyrromethene (BODIPY) as the electron acceptor. Upon excitation, dual emission was observed for CDT-BODIPY with blue and red fluorescence peaks at 463 nm and at 730 nm, respectively, which was ascribed to intramolecular charge transfer (ICT). Due to the ICT effect, the singlet-to-triplet intersystem crossing rate of CDT-BODIPY was also enhanced, leading to an outstanding photodynamic behavior to produce reactive oxygen species (ROS). Meanwhile, its low bandgap also enabled it a moderate photothermal capability with a conversion efficiency of 33.1%. Taking advantage of its phototriggered activities, this conjugated oligomer exhibited an effective inhibition behavior on the pathogenic growth of Escherichia coli ( E. coli ), Staphylococcus aureus ( S. aureus ), and Candida albicans ( C. albicans ), which can be guided by dual-wavelength fluorescence imaging. This D-A-D type conjugated oligomer with balanced photophysical characteristics provides a promising strategy to imaging-guided photoactive therapy.