Experimental and theoretical (DFT) characterization of the excited states and N-centered radical species derived from 2-aminobenzimidazole, the core substructure of a family of bioactive compounds.

Fluorescence spectroscopy, laser flash photolysis (LFP), and density functional theory (DFT) calculations have been performed to understand the photobehavior of 2-aminobenzimidazole (1). The emission lifetime and quantum yield are solvent-dependent. Direct LFP of 1 at 266 nm in MeCN solution results in the generation of a transient identified as radical 1(-H)(*) by comparison with the species generated upon tert-butyl peroxide (ROOR) irradiation in the presence of 1. In addition, a transient assigned as the triplet state is detected in MeOH solution. Theoretical DFT studies on the hydrogen abstraction process support formation of a 1...OR complex, which undergoes nitrogen to oxygen hydrogen transfer, producing the above-mentioned 1(-H)(*) radicals.