Noncovalent bonded 3D structures of eight anhydrous organic salts from tris(hydroxymethyl)aminomethane and organic acids

Cocrystallization of the commonly available organic primary amine, tris(hydroxymethyl)aminomethane (L), with 2-furoic acid (Hfura), isonicotinic acid (Hinic), 4-aminobenzoic acid (Haba), 2,4-dichlorobenzoic acid (Hdcba), 4-chlorophenoxyacetic acid (Hcpa), 1,4-cyclohexanedicarboxylic acid (H2cha), 1,5-naphthalenedisulfonic acid (H2nds) and butane-1,2,3,4-tetracarboxylic acid (H4buta) gave a total of 8 salts having the compositions: (tris(hydroxymethyl)methane): (2-furoic acid) [(HL+) · (fura−)] (1), (tris(hydroxymethyl)aminomethane): (isonicotinic acid) [(HL+) · (inic−)] (2), (tris(hydroxymethyl)aminomethane): (4-aminobenzoic acid) [(HL+) · (aba−)] (3), (tris(hydroxymethyl)aminomethane): (2,4-dichlorobenzoic acid) [(HL+) · (dcba−)] (4), (tris(hydroxymethyl)aminomethane): (4-chlorophenoxyacetic acid) [(HL+) · (cpa−)] (5), (tris(hydroxymethyl)aminomethane): (1,4-cyclohexanedicarboxylic acid) [(HL+) · (Hcha−)] (6), (tris(hydroxymethyl)aminomethane)2: (1,5-naphthalenedisulfonic acid) [(HL+)2 · (nds2−)] (7) and (tris(hydroxymethyl)aminomethane)2: (butane-1,2,3,4-tetracarboxylic acid) [(HL+)2 · (H2buta2−)] (8). The 8 salts have been characterized by XRD, IR and EA, and the melting points of all salts were also gauged. And their structural and supramolecular aspects are fully analyzed. All 8 compounds are ionic, with H-transferring to the N of L. The result reveals that among the 8 investigated crystals the NH2 in L are protonated when the acids are ionized, and the crystal packing is interpreted by the strong charge-assisted N H⋯O H-bond from the NH3+ and the deprotonated acids. Except the N H⋯O H-bond, the O H⋯O H-bonds were also found at all salts. Further analysis of the crystal packing of the salts indicated that a different set of additional C C, O O, CH C, CH2 C, CH CH, C H⋯O/CH2 O, CH Cl, CH2 Cl, CH-π, CH2-π and O-π contacts contribute to the stabilization and expansion of the total structures. For the interplay of the various nonbonding interactions these structures had the homo/hetero supramolecular synthons. Some classical synthons of R22(8), R22(10) and R42(8) were again shown to be involved in making these H-bonding networks.