3-Ammonio-pyridinium tetra-bromido-mercurate(II) monohydrate.

The asymmetric unit of the title compound, (C(5)H(8)N(2))[HgBr(4)]·H(2)O, consists of one cation, one anion and one water mol-ecule. The anion exhibits a distorted tetra-hedral arrangement about the Hg atom. The crystal structure contains alternating sheets of cations (in the ac plane) and stacks of anions. Several strong hydrogen-bonding inter-actions (pyN-H⋯Br and C-H⋯Br; py is pyridine), along with O-H⋯Br inter-actions, connect the sheets of cations to the stacks of anions. Cation-cation π-π stacking is also present (C⋯C distances in the range 3.424-3.865 Å). The shortest Br⋯Br distance is 3.9527 (9) Å.