2-Carboxylatopyridinium–4-nitrophenol (1/1)

In the title 1:1 adduct, C6H5NO3·C6H5NO2, both molecules are almost planar (r.m.s. deviations for the non-H atoms = 0.027 and 0.023 Å for 4-nitrophenol and 2-carboxylatopyridinium, respectively). The pyridine molecule crystallizes as a zwitterion (nominal proton transfer from the carboxylic acid group to the N atom in the ring). In the crystal, inversion dimers of the zwitterions linked by pairs of N—H...O hydrogen bonds generate R22(10) loops; two 4-nitrophenol molecules link to the dimer by O—H...O hydrogen bonds, generating a four-molecule aggregate. These are linked by C—H...O interactions, forming a three-dimensional network

1-Hydroxyisoquinolin-2-ium hydrogen succinate

In the title salt, C9H8NO+·C4H5O4−, the isoquinolinium ring system is approximately planar [r.m.s deviation = 0.011 (2) Å]. In the crystal, adjacent cations and anions are linked by O—H...O and N—H...O hydrogen bonds, forming columns along the b axis. The columns are connected by weak C—H...O interactions into a three-dimensional network