Pyrrolidinium-2-carboxylate–4-nitro- phenol (1/2)

R factor = 0.037; wR factor = 0.094; data-to-parameter ratio = 13.7. In the title compound, C5H9NO22C6H5NO3, the pyrrolidine ring of the pyrrolidinium-2-carboxylate zwitterion adopts a twisted conformation on the –CH2—CH2 – bond adjacent to the N atom. The mean plane of this pyrrolidine ring forms dihedral angles of 25.3 (3) and 32.1 (3) with the two nitrophenol rings. An intramolecular N—H O hydrogen bond occurs in the pyrrolidinium-2-carboxylate molecule. In the crystal, molecules are linked via O—H O and N—H O hydrogen bonds, enclosing R32(8) ring motifs, forming chains running parallel to the a axis. These chains are further cross-linked by O—H O and C—H O hydrogen bonds, forming undulating two-dimensional networks lying parallel to (001). Related literature For the use of nitro-aromatics as intermediates in explosives, dyestuffs, pesticides and organic synthesis, see: Yan et al. (2006). For the occurrence of nitro-aromatics in industrial wastes and as direct pollutants in the environment, see: Yan et al. (2006); Soojhawon et al. (2005). For ring puckering analysis