Abstract: | Ethyl 1‐ethyl‐6‐iodo‐4‐oxo‐1,4‐dihydroquinoline‐3‐carboxylate, C14H14INO3, (I), and ethyl 1‐cyclopropyl‐6‐iodo‐4‐oxo‐1,4‐dihydroquinoline‐3‐carboxylate, C15H14INO3, (II), have isomorphous crystal structures, while ethyl 1‐dimethylamino‐6‐iodo‐4‐oxo‐1,4‐dihydroquinoline‐3‐carboxylate, C14H15IN2O3, (III), possesses a different solid‐state supramolecular architecture. In all three structures, O...I halogen‐bonding interactions connect the quinolone molecules into infinite chains parallel to the unique crystallographic b axis. In (I) and (II), these molecular chains are arranged in (101) layers, viaπ–π stacking and C—H...π interactions, and these layers are then interlinked by C—H...O interactions. The structural fragments involved in the C—H...O interactions differ between (I) and (II), accounting for the observed difference in planarity of the quinolone moieties in the two isomorphous structures. In (III), C—H...O and C—H...π interactions form (100) molecular layers, which are crosslinked by O...I and C—H...I interactions. |