One-step synthesis, characterization and X-ray analysis of benzo[de]benzo[4,5]imidazo[2,1-a]isoquinolin-7-ones

► One-step ring-closure synthesis of benzo[4,5]imidazo[2,1-a]-isoquinolin-7-ones. ► The isomeric compounds were characterized by HRMS, NMR and X-ray crystallography. ► Substituent position influences non-classical intermolecular C-H⋯O interactions. ► Substituent position causes obviously different modes of structure stabilization.