Two tautomeric polymorphs of 2,6‐dichloropurine

Two polymorphs of 2,6‐dichloropurine, C 5 H 2 Cl 2 N 4 , have been crystallized and identified as the 9 H ‐ and 7 H ‐tautomers. Despite differences in the space group and number of symmetry‐independent molecules, they exhibit similar hydrogen‐bonding motifs. Both crystal structures are stabilized by intermolecular N—H...N interactions that link adjacent molecules into linear chains, and by some nonbonding contacts of the C—Cl...π type and by π–π stacking interactions, giving rise to a crossed two‐dimensional herringbone packing motif. The main structural difference between the two polymorphs is the different role of the molecules in the π–π stacking interactions.