Fluorescent dyad for cooperative recognition of copper cation and halogen anion

TMS-ethynyl triazolyl benzothiadiazole (BTD) derivatives have been successfully synthesized by mono deprotection of di-TMS-ethynyl BTD followed by click chemistry. The fluorescence intensity of TMS-ethynyl triazolyl BTD–DCM dyad 8, as well as triazolyl BTD 3, and the DCM derivative 7 could be selectively quenched by Cu2+, but almost not affected by different tested anions. Interestingly, the fluorescence emission of DCM-based fluorophores 7 and 8 was highly sensitive to a combination of Cu2+, F−, or Br− in a sequence dependent manner. With the dyad 8, the detection limit as low as 0.13 ppb could be attained for F− in MeCN. The Cu2+-promoted aerobic oxidative dimerization of DCM moiety to tetrahydrofuran derivatives has also been demonstrated for the first time.