Single-crystal and molecular structures of six hydrogen-bonding 3D supramolecular salts from 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, and acidic components

Cocrystallization experiments of the commonly available 2-aminobenzoic acid/3-aminobenzoic acid/4-aminobenzoic acid, with a series of organic acids gave a total of six anhydrous molecular salts. The structures of these salts were subsequently characterized by IR, EA, and XRD analysis technique, and the melting points of all salts were also reported. In the six salts, the NH2 of the aminobenzoic acids are protonated when the organic acids are deprotonated, and the crystal packing is interpreted in terms of strong NH⋯O H-bonds from the NH3+ and deprotonated acidic groups. Except the NH⋯O H-bond, the OH⋯O H-bonds were also found at 1–6. The salts of the aryl sulfonates exhibited the NH⋯S H-bonds, and salt 4 has the additional OH⋯S H-bond. In these structures homo or hetero supramolecular synthons or both were produced, making R12(3), R12(5), R12(7), R21(6), R22(4), R22(5), R22(8), R22(12), R22(16), R23(6), R32(7), R32(9), R33(8), R33(9), R33(10), R42(8), R42(18), R42(14), R44(12), R44(22), R65(18), and R66(26) rings which could have important function in the formation and stabilization of the crystals. But not all of them were appeared repeatedly, as most of them occurred only in some structures. Nevertheless R42(8), R43(10) and R44(12) usually observed in organic solids of organic acids with amine, were again shown to be involved in most of these H-bonding networks. Further inspection into the crystal packing of the salts indicated that a large variety of different secondary interactions were also existed in 1–6, which contribute to the stabilization and expansion of the total 3D framework structures.