Anion Sensing with a Blue Fluorescent Triarylboron-Functionalized Bisbenzimidazole and Its Bisbenzimidazolium Salt

摘要

A blue fluorescent p -dimesitylboryl-phenyl-functionalized 1,3-bisbenzimidazolyl benzene molecule (1 ) has been synthesized in high yield by Stille coupling of bisbenzimidazolyl bromobenzene with p -BMes_(2)-SnBu_(3)-benzene. Methylation of 1 led to the formation of the bisbenzimidazolium salt (2 ). The utility of both 1 and 2 in sensing CN~(–) and halide (F~(–), Cl~(–), Br~(–), and I~(–)) was examined, and it was found that only the small fluoride and cyanide anions were able to bind to the boron atom with binding constants in the range of 2.9 × 10~(4) to 5 × 10~(5) M~(–1). Computational studies provided insight into the photophysical properties of the molecules and verified that a charge-transfer process is quenched in these “turn-off” molecular sensors.