Supramolecular synthesis by cocrystallization of oxalic and fumaric acid with diazanaphthalenes

1:1 cocrystals of oxalic and fumaric acid with 1,4-diazanaphthalene (quinoxaline) and 2,3-diazanaphthalene (phthalazine) were prepared. 1,5-Diazanaphthalene (naphthyridine) formed a 1:1 cocrystal only with oxalic acid. X-ray structural analyses are reported. The influence of the position of the two nitrogen atoms in these diazanaphthalenes on the crystal packing is analyzed. The gross crystal structure is governed by strong (OHN)-N-... hydrogen bonds. The fine-tuning of the packing of the cocrystals of quinoxaline with oxalic and fumaric acid occurs via (CHO)-O-... hydrogen bonds. The stabilization by the (CHO)-O-... hydrogen bonds leads to a planar sheetlike structure in the cocrystal with fumaric acid, in contrast to the cocrystal with oxalic acid where the optimization of the (CHO)-O-... hydrogen bonds results in a nonplanar bent structure. The geometrical arrangement of the nitrogen atoms in land 5-positions in naphthyridine allows a planar sheetlike structure in the cocrystal with oxalic acid. In the case of phthalazine complete proton transfer from one carboxy group of oxalic and fumaric acid to a nitrogen atom of the heterocycle, generating ionic interactions is observed. The hydrogen atom of the second carboxy group of the acids is involved in a (OHO)-O-...=C hydrogen bond.