The molecular packing structure of PR3Y (a) showing the one-dimensional columns (blue box) formed by π–π interactions (orange box), the interactions between chains formed by halogen-bonding interactions (green dotted line) and the CH⋯π interactions (blue dotted line) between the columns (left). Packing of molecules viewed along the  direction (right). (b) A pair of molecules on the (011) plane that contribute the most significantly to the lattice stabilization. The lattice energy was calculated by dividing into A and B sets due to the disorder of one of the propyl substituents. The red molecule represents the reference molecule.