Trimer formation of 6-methyl-1,3,5-triazine-2,4-diamine in salt with organic and inorganic acids: analysis of supramolecular architecture

Abstract

Although the numbers of co-crystals, salts, polymorphs, hydrates, and solvates are growing steadily, trimers that contain both inorganic and organic acids are still very rare in the Cambridge Structural Database (CSD). When 3,5-dihydroxybenzoic acid was crystallized readily with 6-methyl-1,3,5-triazine-2,4-diamine in a 4:3 ratio of ethanol and water by adding a few drops of nitric acid upon slow evaporation in ambient conditions, 6-methyl-1,3,5-triazine-2,4-diamine and 3,5-dihydroxybenzoic acid with the nitric acid form of 1:1:1 an inorganic-organic salt formulated as [(C4H8N5 +)·(NO3 −)·(C7H6O4)]. The supramolecular architecture, which is quite elegant and simple, appeared as stacking of a 3D network in adduct. Proton transfer from the HNO3 to 6-methyl-1,3,5-triazine-2,4-diamine N acceptor (triazine N) occurred in the organic salt and led to the ionic heterosynthon in the structure. Cooperation among the -COOH, -OH, NO3-, and -NH-functional groups for the observed hydrogen bond synthon was examined in the structure. In adduct, recognition among the constituents is established through N-H⋯O, O-H⋯N, and O-H⋯O hydrogen bonds. The agomelatine molecules are linked through the intermolecular hydrogen bonding interactions (O-H⋯O) to form a 1D chain. In addition, the nitric acid anions and base cations act as donors and acceptors of hydrogen bonds and interlink, almost to co-planarity, the hydrogen-bonded chains through interchain N-H⋯O, O-H⋯N, as well as O-H⋯O interactions into a 2D sheet structure. Persistent N-H⋯O interactions were found to play an important role in the formation of the final 3D array. The salt was characterized by elemental analysis, IR, thermogravimetric analysis, and single-crystal X-ray diffraction, to better understand how intermolecular interactions influence its supramolecular assembly.