title: Crystal structure of 1H,1'H-[2,2'-biimid-azol]-3-ium hydrogen tartrate hemi-hydrate.
abstract: In the crystal of the title hydrated salt, C6H7N4 (+)·C4H5O6 (-)·0.5H2O, the bi-imidazole monocation, 1H,1'H-[2,2'-biimidazol]-3-ium, is hydrogen bonded, via N-H⋯O, O-H⋯O and O-H⋯N hydrogen bonds, to the hydrogen tartrate anion and the water mol-ecule, which is located on a twofold rotation axis, forming sheets parallel to (001). The sheets are linked via C-H⋯O hydrogen bonds, forming a three-dimensional structure. There are also C=O⋯π inter-actions present [O⋯π distances are 3.00 (9) and 3.21 (7) Å], involving the carbonyl O atoms and the imidazolium ring, which may help to consolidate the structure. In the cation, the dihedral angle between the rings is 11.6 (2)°.
authors.affiliation: Department of Chemistry, Taiyuan Normal College, Taiyuan, Shanxi 030031, People's Republic of China.
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Gao
authors.affiliation: Department of Chemistry, Taiyuan Normal College, Taiyuan, Shanxi 030031, People's Republic of China.
authors.forename: Li-Fang
authors.initials: LF
authors.lastname: Bian
authors.affiliation: Department of Chemistry, Taiyuan Normal College, Taiyuan, Shanxi 030031, People's Republic of China.
authors.forename: Shao-Wei
authors.initials: SW
authors.lastname: Guo
keywords: bi­imidazole; crystal structure; hydrogen bonding; imidazolium; tartrate