ABSTRACT
Two new crystalline salts, namely, hypoxanthinium bromide monohydrate, C5H5N4O+·Br-·H2O (I) and xanthinium bromide monohydrate, C5H5N4O2 +·Br-·H2O (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-Hâ¯O, N-Hâ¯Br, C-Hâ¯Br and O-Hâ¯Br inter-actions described by R 2 3(9) and R 2 2(8) synthons. The crystal packing is also consolidated by carbon-ylâ¯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 Brâ¯H/Hâ¯Br contacts (22.3% in I and 25.4% in II) .