In this report, research on π-stacking synthon repetitivity and the effect of substituents in the crystal structures of HgX₂ complexes of N-(1-chloro/bromo-naphthalen-4-yl)pyrazine-2-carboxamide ligands is described. Structural analysis shows that these compounds have almost the same propensity for the formation of π–π interactions in supramolecular crystal structures.