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

摘要

Crystal: [2(C_(12)H_(16)0_6)~2_4(C_3H_7N_6)~_5(H_20)] is composed of two doubly deprotonated Kemp's triacid molecules (KTA~2), four singly protonated melamine (MEL-H~+) and five water molecules. In the crystal structure, protonated (MEL-H~+) moieties are interconnected via N_H. ..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 KTA~2 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.