Bis(N,N′,N′′-triisopropyl­guanidinium) fumarate–fumaric acid (1/1)

The asymmetric unit of the title compound, C(10)H(24)N(3) (+)·0.5C(4)H(2)O(4) (2−)·0.5C(4)H(4)O(4), comprises a triisopropyl­guanidinium cation, half of a fumarate dianion and half of a fumaric acid mol­ecule; both the fumarate dianion and the fumaric acid mol­ecule are located on inversion centres. In the crystal, inter­molecular O—H⋯O hydrogen bonds between the carboxyl groups of the fumaric acid mol­ecules and the carboxyl­ate groups of the fumarate anions lead to the formation of a hydrogen-bonded supra­molecular twisted chain along the b axis. The triisopropyl­guanidinium cations inter­act with the fumarate–fumaric acid chains via extensive N—H⋯O and C—H⋯O hydrogen bonds, leading to a ladder arrangement, with the cation being the rungs that bridge three curled chains of fumarate–fumaric acid. The crystal packing is stabilized by N—H⋯O and C—H⋯O (cation⋯fumarate/fumaric) and O—H⋯O (fumarate⋯fumaric) hydrogen bonds, consolidating a three-dimensional network.