A study of the crystal structures, supra-molecular patterns and Hirshfeld surfaces of bromide salts of hypoxanthine and xanthine.

Two new crystalline salts, namely, hypoxanthinium bromide monohydrate, C(5)H(5)N(4)O(+)·Br(-)·H(2)O (I) and xanthinium bromide monohydrate, C(5)H(5)N(4)O(2) (+)·Br(-)·H(2)O (II), were synthesized and characterized by single-crystal X-ray diffraction technique and Hirshfeld surface analysis. The hypoxanthinium and xanthinium cations in salts I and II are both in the oxo-N(9)-H tautomeric form. The crystal packing of the two salts is governed predominantly by N-H⋯O, N-H⋯Br, C-H⋯Br and O-H⋯Br inter-actions described by R (2) (3)(9) and R (2) (2)(8) synthons. The crystal packing is also consolidated by carbon-yl⋯π inter-actions between symmetry-related hypoxanthinium (HX(+) ) cations in salt I and xanthinium cations (XA(+) ) in salt II. The combination of all these inter-actions leads to the formation of wave- and staircase-like architectures in salts I and II, respectively. The largest contributions to the overall Hirshfeld surface are from Br⋯H/H⋯Br contacts (22.3% in I and 25.4% in II) .