1,10-Phenanthrolin-1-ium 2-carboxy-4-nitro­benzoate

The cation of the title salt, C₁₂H₉N·C₈H₄NO, is a monoprotonated 1,10-phenanthroline mol­ecule, whereas its anion is a monodeprotonated 4-nitro­phthalic acid mol­ecule. There is a strong, almost symmetrical, intramolecular hydrogen bond linking the O atoms of neighbouring carboxyl­ate groups within the anion [O—H = 1.13 (4) Å, H...O = 1.27 (4) Å, O...O = 2.395 (3) Å and O—H...O = 173 (4)°]. An N—H...O bond [N—H = 1.00 (3) Å, H...O = 1.70 (3) Å, N...O = 2.668 (3) Å and N—H...O = 160 (3)°] is responsible for formation of ion pairs, which are further loosely aggregated into a three-dimensional framework via C—H...O and π–π interactions.

1,10-Phenanthrolin-1-ium 2-carboxy-6-nitro­benzoate

In the title salt, C₁₂H₉N₂⁺·C₈H₄NO₆⁻, one N atom of 1,10-phenanthroline is protonated [N—H = 1.00 (2) Å], while the other N atom is not. Protonation of the N atom causes the C—N—C angle to increase [122.3 (2)° in the protonated ring versus 116.2 (2)° in the unprotonated ring]. In the crystal structure, N—H...O and O—H...O hydrogen bonds and van der Waals forces stabilize the packing of the ions.

N-(2-Nitro­phen­yl)-1-oxo-2,6,7-trioxa-1-phosphabicyclo­[2.2.2]octa­ne-4-carboxamide

In the title compound, C₁₁H₁₁N₂O₇P, compression of the P—O—C angles is observed, suggesting that some strain is probably present. The configuration around phosphorus is distorted tetra­hedral. In the crystal structure, N—H...O and C—H...O hydrogen-bond contacts and van der Waals forces stabilize the packing of the compound.

4-Methyl­piperazin-1-ium 2-amino-5-iodo­benzoate

In the title salt, C₅H₁₃N₂⁺·C₇H₅INO₂⁻, the packing of the ions is stabilized by N—H...O hydrogen bonds and van der Waals forces.

N-(3-Nitro­phen­yl)-1-oxo-2,6,7-trioxa-1-phosphabicyclo­[2.2.2]octane-4-carboxamide dimethyl­formamide solvate

In the crystal structure of the title compound, C₁₁H₁₁N₂O₇P, the carboxamide mol­ecule and the solvent mol­ecule of crystallization each possess mirror symmetry; for the former, the mirror plane bisects the two-ring OP(OCH₂)₃C cage. The packing is stabilized by an inter­molecular N—H...O hydrogen bond and a number of C—H...O hydrogen bonds.