Benzimidazoazapurines: Design, Synthesis, and Photophysical Study

Abstract

A highly efficient approach to a new class of polycyclic 8-azapurines, benzo[4,5]imidazo[1,2-<i>a</i>][1,2,3]triazolo[4,5-<i>e</i>]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-<i>a</i>]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.