Design and synthesis of single-benzene-based fluorophores with red/NIR emission for dual-function optical waveguides and photodynamic therapy

Abstract

Photodynamic therapy (PDT) is an emerging cancer treatment that relies on the interaction between light, a photosensitizer (PS) and ground state oxygen, which combine to generate cytotoxic singlet oxygen species for cell death. Conventional PSs often suffer from aggregation-caused quenching (ACQ) due to their planar molecular structures, which limits their effectiveness. Here, we report the first single-benzene-based fluorophore (SBF) designed by systematically tuning the positions and quantities of electron-donating and electron-withdrawing groups, achieving efficient red/near-infrared (NIR) emission, dual-state emission, optical waveguide properties, and excellent PDT effects. Two SBFs, wx-1 and wx-2, were synthesized via a straightforward method, with wx-1 exhibiting superior optical properties in both solution and crystalline states. Specifically, wx-1 demonstrated two polymorphs: polymorph A (orange emission, λ_em = 600 nm, Φ_F = 0.07) and polymorph B (NIR emission, λ_em = 657 nm, Φ_F = 0.12). Polymorph B also showed potential as an NIR optical waveguide. Furthermore, wx-1 exhibited a strong ability to generate singlet oxygen in the solution state, effectively eradicating EMT6 tumor cells under white light irradiation. This study provides a novel approach to designing SBFs with red/NIR emissions and highlights their potential in optical waveguide and PDT applications.