C-halogen...pi dimer and C-H...pi interactions in 1-(2-bromo-4,5-dimethoxybenzyl)-2-butyl-4-chloro-1H-imidazole-5-carbaldehyde and 2-butyl-4-chloro-1-(6-methyl-1,3-benzodioxol-5-ylmethyl)-1H-imidazole-5-carbaldehyde.

The structures of the title compounds, C17H20BrClN2O3, (I), and C17H19ClN2O3, (II), are stabilized by intramolecular C-H...O and C-H...pi interactions. The stability of the molecular packing in (I) and (II) arises from a diverse set of weak intermolecular C-H...O, C-H...pi and C-halogen...pi interactions. In the crystal structure of (I), molecules aggregate in dimeric subunits via C-Br...pi interactions. The dimers are interlinked by C-H...O hydrogen bonds. The halogens cluster together and form a channel along the b axis. In (II), the packing is mainly governed by intermolecular C-H...O and C-H...pi interactions.