Crystal structures and Hirshfeld surface analyses of hypoxanthine salts involving 5-sulfosalicylate and perchlorate anions

Two salts of 1,9-di­hydro­purin-6-one (hypoxanthine), namely, 6-oxo-1,9-di­hydro­purin-7-ium 5-sulfosalicylate dihydrate, C(5)H(5)N(4)O(+)·C(7)H(5)O(6)S(−)·2H(2)O, (I), and 6-oxo-1,9-di­hydro­purin-7-ium perchlorate monohydrate, C(5)H(5)N(4)O(+)·ClO(4) (−)·H(2)O, (II), have been synthesized and characterized using single-crystal X-ray diffraction and Hirshfeld analysis. In both salts, the hypoxanthine mol­ecule is protonated at the N7 position of the purine ring. In salt (I), the cation and anion are connected through N—H⋯O inter­actions. The protonated hypoxanthine cations of salt (I) form base pairs with another symmetry-related hypoxanthine cation through N—H⋯O hydrogen bonds with an R (2) (2)(8) ring motif, while in salt (II), the hypoxanthine cations are paired through a water mol­ecule via N—H⋯O and O—H⋯N hydrogen bonds with an R (3) (3)(11) ring motif. The packings within the crystal structures are stabilized by π–π stacking inter­actions in salt (I) and C—O⋯π inter­actions in salt (II). The combination of several inter­actions leads to the formation of supra­molecular sheets extending parallel to (010) in salts (I) and (II). Hirshfeld surface analysis and fingerprint plots reveal that O⋯H/H⋯O contacts play the major role in the crystal packing of each of the salts, with a 54.1% contribution in salt (I) and 62.3% in salt (II).