Abstract
The constituents of the title 1:1 co-crystal, C(7)H(6)O(2)·C(14)H(12)N(2), are connected into dimeric aggregates by a bifurcated O-H⋯N hydrogen bond; the hydroxyl-H atom is hydrogen bonded to the two N atoms of the 2,9-dimethyl-phenanthroline. The hydrogen-bonded residues are almost orthogonal to each other [dihedral angle = 78.56 (7) °]. In the crystal packing, the aggregates are assembled into layers in the bc plane by π⋯π inter-actions [ring centroid⋯ring centroid distance = 3.5577 (16) Å] involving the pyridyl rings, and C-H⋯π contacts involving the phenanthroline-H atom and the phenyl ring of the acid.