Hydrogen bonded 1D-3D supramolecular structures from Benzylamine and organic acidic components

Abstract

Cocrystallization of the commonly available organic amine, benzylamine, with a series of organic acids afforded a total of seven organic salts with the compositions: (benzylamine)2: (p-nitrophenol)2: (H2O) (1) [(HL)2+⋯(npl−)2⋯(H2O), npl− = p-nitrophenolate], (benzylamine): (4-tert-butylbenzoic acid) (2) [(HL+)⋯(tba−), tba− = 4-tert-butylbenzoate], (benzylamine): (3,4-dichlorobenzoic acid) (3) [(HL+)⋯dcba−), dcba− = 3,4-dichlorobenzoate], (benzylamine): (2,5-dihydroxybenzoic acid) (4) [(HL+)⋯(dhba−), dhba− = 2,5-dihydroxybenzoate], (benzylamine): (2-bromo-but-2-enedioic acid) (5) [(HL+)⋯(Hbba−), Hbba- = 2-bromo-hydrogenbut-2-enedioate], (benzylamine): (2,6-pyridinedicarboxylic acid) (6) [(HL+)⋯(Hpdc−), Hpdc- = 2,6-pyridine hydrogendicarboxylate], and (benzylamine)2: (3-nitrophthalic acid): 2(H2O) (7) [(HL+)2⋯(npa2−)⋯(H2O)2, npa2− = 3-nitrophthalate]. The seven salts have been characterised by X-ray diffraction analysis, IR, and elemental analysis, and the melting points of all the salts were also reported. And their structural and supramolecular aspects are fully analyzed.The results reveal that among the seven investigated crystals the NH2 in the benzylamine are protonated when the organic acids are deprotonated, and the crystal packing is interpreted in terms of the strong charge-assisted NH⋯O hydrogen bond between the NH3+ and deprotonated acidic groups. Except the NH⋯O hydrogen bond, the OH⋯O hydrogen bonds (charge assisted or neutral) were also found at the salts 1, 4, 5, 6, and 7. Further analysis of the crystal packing of the salts indicated that a different family of additional CHO/CH2O, CH-π/CH2-π, Cπ-Cπ, OO, O-Cπ, O-π, and Cl-π associations also contribute to the stabilization and expansion of the total high-dimensional framework structures. For the coexistence of the various weak nonbonding interactions, these structures adopted a variety of supramolecular synthons of R12(4), R12(5), R21(5), R22(6), R22(10), R32(6), R32(9), R33(9), R42(8), R42(9), R43(10), R44(12), R44(20), R52(9), and R64(12).