Functionalization and solubilization of polycyclic aromatic compounds by sulfoniumization

Despite their unique physical properties and diverse applications in materials science, poor solubility of polycyclic aromatic hydrocarbons (PAHs) limits further fine-tuning and investigation of these systems. Herein, we report a sulfoniumization strategy to solubilize and functionalize a diverse range of PAHs in a one-step protocol using a triethylene glycol ether-substituted diaryl sulfoxide. While mono-sulfoniumization is generally observed, modification of the reaction conditions to favor bis-sulfoniumization is shown. The downstream applicability of the resulting PAH sulfonium salts is validated through a series of post-functionalization reactions that include C-C and C-heteroatom bond formation, while their application in annulative π-extension (APEX) is showcased by the synthesis of tetra-<i>tert</i>-butylquaterrylene from perylene. The red-shifted absorption and fluorescence, along with high water solubility of the PAH sulfonium salts, enable their application in bio-imaging, where they demonstrate selective mitochondrial staining without cytotoxicity.