4,4'-(Ethene-1,2-diyl)dipyridinium bis(2-hy-droxy-3-meth-oxy-benzoate).

In the title double proton-transfer salt, C 12 H 12 N 2 2+ ·2C 8 H 7 O 4 - , consisting of a 1:2 ratio of 4,4'-(ethene-1,2-diyl)dipyridinium cations ( trans bipyridinium ethyl-ene) to 2-hy-droxy-3-meth-oxy-benzoate anions ( o -vanillate), the complete cation is generated by crystallographic inversion symmetry and it is linked to adjacent o -vanillate anions by N-H⋯O hydrogen bonds, forming trimolecular assemblies. The trimers are linked by C-H⋯O hydrogen bonds as well as aromatic π-π stacking inter-actions into a three-dimensional network. The anion features an intra-molecular O-H⋯O hydrogen bond.