4-Nitrophenol–piperazine (2/1)

In the title adduct, C6H5NO3·0.5C4H10N2, the piperazine ring possesses inversion symmetry and has a chair conformation. Its mean plane makes a dihedral angle of 65.45 (7)° with the 4-nitrophenol ring. In the crystal, the piperazine ring is linked to two 4-nitrophenol molecules via O—H...N hydrogen bonds. The molecules are also linked via bifurcated N—H...(O,O) hydrogen bonds involving the NO2 O atoms, forming a two-dimensional network lying parallel to (102). The networks are linked via C—H...O hydrogen bonds, forming a three-dimensional structure