Three 3D Supramolecular Organic Salts Assembled from Melamine and Aliphatic Carboxylic Acids: Preparation, Crystallographic Characterization, and Hirshfeld Surface Analysis

Three crystalline organic salts (melamine)2: (itaconic acid): 3H2O [(Hmem)22+·(itca2−)·(H2O)3, itca2− = itaconate] (1), (melamine)2:(2-bromo-but-2-enedioic acid):DMF:2H2O [(Hmem+)2·(bbda2−)·DMF·(H2O)2, bbda2− = 2-bromo-but-2-enedioate] (2) and (melamine):(α-ketoglutaric acid) [(Hmem+)·(Hketglua−), Hketglua− = hydrogen α-ketoglutarate] (3) were featured by X-ray diffraction analysis, IR, mp, and elemental analysis. Significant non-covalent interactions were calculated by means of the Hirshfeld surface analysis. All salts involve extensive N–H···OH-bonds as well as other non-covalent associations. The melamine polymers/dimers were set up at 1–2/3 by the pair of complmentary N–H···NH-bonds. The role of these non-covalent interactions in the crystal packing is ascertained. These weak interactions combined, all salts exhibited 3D framework motifs. The crystal structures of the salts from melamine, itaconic acid, 2-bromo-but-2-enedioic acid and α-ketoglutaric acid are predominantly stabilized by the classical hydrogen bonds as well as CH2···O, CH3···O, Br···Br, C···C, O···C, and π···π interactions.