Abstract: | A high yield one pot synthesis of 2‐(2‐hydroxyaryl)‐1H‐benzirrndazole derivatives by 2‐hydroxy aromatic aldehydes with aromatic 1,2‐diamines in the presence of manganese(III) acetate at room temperature was developed. Nine fluorescencers 2‐(2‐hydroxyaryl)‐1H‐benzirrndazoles with substituent(s) X (X = H, CH3, CH3O, Cl) and two fluorescencers 2‐(2‐hydroxyaryl)‐1H‐naphth[2,3‐d]imidazoles with substituent of H or Cl were prepared in 38–87% yield and the ultraviolet absorption and fluorescent spectra of the eleven compounds synthesized were measured in methanol. The fluorescent characteristics of the 2‐(2‐hydroxyaryl)benzimidazole derivatives prepared were investigated on the basis of excited‐state intramolecular proton transfer mechanism, Stokes' shift, quantum yield, and the relationship between fluorescent intensity and the substituents were derived. |