The synthesis and photophysical properties of halide sensitive acridizinium dyes

A series of acridizinium (benzo[b]quinolizinium) salts containing methoxy, fluoro and chloro substituents were synthesized and their spectroscopic properties and sensitivity towards halide quenching in water were determined. The salts have substantially improved properties over the commonly employed quinolinium and acridinium fluorophores for the sensing of bromide and iodide ions. Of the substituted acridiziniums investigated, 8,10-difluoro-acridizinium bromide has the best combination of properties as a bromide or iodide sensor.