Crystal structure of propane-1,3-diaminium squarate dihydrate.

Propane-1,3-diaminium squarate dihydrate, C 3 H 12 N 2 2+ ·C 4 O 4 2- ·2H 2 O, results from the proton-transfer reaction of propane-1,3-di-amine with squaric acid and subsequent crystallization from aqueous medium. The title compound crystallizes in the tetra-gonal crystal system (space group P 4 bm ) with Z = 2. The squarate dianion belongs to the point group D 4 h and contains a crystallographic fourfold axis. The propane-1,3-diaminium dication exhibits a C 2 v -symmetric all- anti conformation and resides on a special position with mm 2 site symmetry. The orientation of the propane-1,3-diaminium ions makes the crystal structure polar in the c- axis direction. The solid-state supra-molecular structure features a triperiodic network of strong hydrogen bonds of the N-H⋯O and O-H⋯O types.