Hydrogen Peroxide Sensors Based on Fluorescence Quenching of the 2-AminobenzimidazoleFluorophore.

The fluorescence emission of the parent 2-aminobenzimidazole (ABZ, ), the mono- and disubstituted derivatives (, ), 2-aminonaphthoimidazole (), and 4-amino dinaphthodiazepine (λ = 315-400 nm) is strongly quenched in the presence of aqueous hydrogen peroxide. The quenching process is dual: for diazepine , quenching is dynamic at lower HO concentrations with linear reduction of the fluorescence lifetime from 4.3 to 2.6 ns. At higher HO concentrations, a second species appears in the absorption and emission spectra with fluorescence lifetimes of 1.3 ns, indicating the formation of a new (ground-state) hydrogen-bonded ABZ-HO complex (static quenching). Sensors and show also dual quenching that fits with a static 1:1 and 1:2 model with = 8(11) M and = 21(147) M for (). The formation of a 1:2 complex (:(HO)) is also supported by density functional theory (DFT) calculations and spectra simulations.