Structure and spectroscopy of imidazo [1,2-a]imidazoles andimidazo[1,2-a]benzimidazoles

Abstract

Two azapentalenes containing fused imidazoles have been synthesized and their NMR (solution and solid state) and UV properties recorded. Tautomerism in the case of imidazo[1,2-a]benzimidazole (9H tautomer) and the structure of the cations resulting from protonation in both cases have been determined. Ab initio calculations (HF/6-311G**) confirm the greater stability of 9H over 1H- imidazo[1,2-a]benzimidazole tautomer.