2-[(4-Hydroxy-phen-yl)diazen-yl]benzoic acid-N,N'-bis-(4-pyridylmeth-yl)oxamide (2/1).

The asymmetric unit of the title co-crystal, 2C(13)H(10)N(2)O(3)·C(14)H(14)N(4)O(2), comprises one mol-ecule of 2-(4-hydroxy-phenyl-diazen-yl)benzoic acid and half of an N,N'-bis-(4-pyridylmeth-yl)oxamide mol-ecule as the latter is disposed about an inversion centre. The most notable feature of the crystal structure is the formation of supra-molecular chains arising from hydr-oxy-pyridine O-H⋯N contacts and amide-hydr-oxy C-H⋯O contacts. These give rise to 40-membered {⋯OH⋯NNC(4)OH⋯NC(4)NC(2)NH}(2) synthons, generating supra-molecular chains along [01]. The chains are connected into a two-dimensional array via C-H⋯π inter-actions. Layers, with a step-ladder topology, are consolidated into the crystal structure via further C-H⋯π inter-actions.