1,2-Bis(pyridin-4-yl)ethene-4-hy-droxy-3-meth-oxy-benzoic acid (1/1).

In the title 1:1 co-crystal [alternatively called bi-pyridine ethyl-ene-p-vanillic acid (1/1)], C(12)H(10)N(2)·C(8)H(8)O(4), the dihedral angle between the pyridine rings is 59.51†(5)°. In the crystal, the mol-ecules are linked by O-H⋯N hydrogen bonds, generating [401] chains of alternating C(12)H(10)N(2) and C(8)H(8)O(4) mol-ecules.