1,2-Bis(pyridin-4-yl)diazene-3,4,5-trihy-droxy-benzoic acid-methanol (3/2/2).

The title compound, 3C(10)H(8)N(4)·2C(7)H(6)O(5)·2CH(4)O, has a mol-ecular crystal structure which results from the cocrystallization of gallic acid (GA), 4,4'-azodipyridine (AzPy) and methanol in a 2:3:2 molar ratio. The asymmetric unit comprises one molecule each of GA, AzPy and methanol in general positions and half a molecule of AzPy as this is located about a centre of inversion. In the crystal, all the components of the structure are associated via the extended system of hydrogen bonds (O-H⋯O and O-H⋯N) and π-π stacking inter-actions [centroid-centroid distance = 3.637†(3)†à ] into two-dimensional supra-molecular layers which are packed parallel to the [101] plane. The shortest perpendicular distance and the slippage between aromatic groups are 3.395†(3) and 2.152†(3)†à , respectively. The AzPy mol-ecules display a trans conformation with respect to the azo groups.