Melaminium phthalate.

The crystals of the new melaminium salt, 2,4,6-triamino-1,3,5-triazin-1-ium hydrogenphthalate, C3H7N6+.C8H5O4-, are built up from single protonated melaminium residues and single dissociated hydrogenphthalate(1-) anions. The protonated melaminium ring is almost planar. The best plane through the non-dissociated carboxyl group (COOH) of the hydrogenphthalate(1-) anion is inclined at an angle of 16.4 (2) degrees to the plane of the six-membered hydrogenphthalate ring, while the plane of the ionized COO- group is roughly perpendicular [84.2 (2) degrees ] to this plane. A combination of ionic and donor-acceptor hydrogen-bond interactions linking together the melaminium and hydrogenphthalate residues forms a three-dimensional network.