The crystal structure of the title mol-ecular salt, C5H11N3 (+)·2Cl(-), was redetermined. In comparison with the previous study [Bonnet et al. (1975 ▸). Bull. Soc. Fr. Mineral. Crist. 98, 208-213.], the positions of some H atoms were corrected, allowing a more accurate description of the hydrogen-bonding scheme. In addition, the absolute structure was also determined. The maximum differences in terms of bond lengths and angles between the two determinations are 0.022 Å and 1.43°, respectively. The organic cation display a anti conformation of the protonated amine function and the imidazolium ring. The dihedral angle between the imidazolium plane and the plane through the C-C-N side chain is 29.58 (3)°. In the crystal, the organic cations and Cl(-) anions are stacked alternatively into layers parallel to (100). N-H⋯Cl hydrogen bonds between all H atoms of the ammonium group and both N-H groups of the imidazolium ring and the Cl(-) acceptor anions lead to the linkage of organic and inorganic layers into a three-dimensional network.
Keywords: crystal structure; histamine; hydrogen bonding; redetermination.