Benzimidazoazapurines: Design, Synthesis, and Photophysical Study

A highly efficient approach to a new class of polycyclic 8-azapurines, benzo[4,5]imidazo[1,2- a ][1,2,3]triazolo[4,5- e ]pyrimidines (BITPs), with good photophysical characteristics is proposed. The approach comprises condensation of aminobenzimidazoles with 3-oxo-2-phenylazopropionitrile to form 3-(arylazo)benzo[4,5]imidazo[1,2- a ]pyrimidine-4-amines, which undergo oxidative cyclization by the catalytic action of copper(II) acetate, resulting in BITPs with 73–84% yield. Spectral investigations demonstrated the fluorescent properties of BITPs, exhibiting good quantum yields (up to 60%) with maxima absorption at 379–399 and emission at 471–505 nm.