Crystals of the Kemp’s triacid salts. Part IV: Supramolecular architecture in the crystal of tetra(melaminium) bis(5-carboxy-1,3,5-trimethylcyclo-hexane-1,3-dicarboxylate) pentahydrate

Crystal: [2(C12H16O6)2−·4(C3H7N6)+·5(H2O)] is composed of two doubly deprotonated Kemp’s triacid molecules (KTA2), four singly protonated melamine (MEL-H+) and five water molecules. In the crystal structure, protonated (MEL-H+) moieties are interconnected via NH⋯N hydrogen bonds into polymeric 1D-chain and form a stacking structure. The rings of the KTA dianionic molecules exhibit a chair conformation with all three carboxylic groups in the axial positions and all three methyl groups in the equatorial positions. In the KTA2 anion, one strong and almost symmetrical intramolecular hydrogen bond is present. In the crystal of the complex, hydrogen-bonded chains involving intermolecular hydrogen bonds are formed. The water molecules act as proton-donors and proton-acceptors in three-dimensional hydrogen-bonded network within the supramolecular complex. The IR spectrum of the crystal is consistent with the results obtained by the X-ray study and provides spectroscopic evidence for the crystal formation.