Aromatic dicarboxylic acids as building blocks of extended hydrogen-bonded architectures

An examination of the crystal structures of four compounds, 5-amino iso-phthalic acid hemihydrate (monoclinic, P2(1)/n, a=8.142(2), b=17.444(3), c=11.140(2) Angstrom, beta=94.19(3)degrees, D-c 1.601 g cm(-3), Z=8, R-w(2) = 0.106 for 1401 unique reflections), piperazinium(2+) 5-amino iso-phthalate (monoclinic, P2(1)/c, a=11.820(2), b=9.516(2), c=12.618(3) Angstrom, beta = 116.70(3)degrees D-c = 1.400 g cm(-3), Z= 4, R-w(2)= 0.104 for 2222 unique reflections), 2-chloro-benzylammonium 2-carboxylate-6-carboxylic pyridine (monoclinic, P2(1)/c, a=22.391(2), b=9.322(3), c=13.274(2) Angstrom, beta=92.567(11), D-c=1.482 g cm(-3), Z= 8, R-w(2) = 0.113 for 3610 unique reflections), and 3-fluoro-benzylammonium 2-carboxylate-6-carboxylic pyridine hydrate (monoclinic, P21/c, a=9.862(2), b=13.246(3), c=21.153(4) Angstrom, beta=98.00(3), D-c = 1.463 g cm(-3) Z=8, R-w(2) = 0.154 for 2552 unique reflections), has identified a robust hydrogen-bonded, ribbon-like motif, generated by the geometric fit and hydrogen-bond complementarity of the [-COO](-) and the [-COOH] functionalities. This preferred interaction between neighbouring anions results in infinite 1-D anionic architectures that are held together by short and near-linear O-H ... O hydrogen bonds. In 1 and 2, the amino functionality acts as a crosslink (through N-H ... O interactions) between adjacent sheets, thereby generating extended 2-D architectures. 5-Amino iso-phthalic acid exists as a zwitterion in the solid state, an observation which was also indicated by vibrational spectroscopic data. The crystal packing in both 3 and 4 consists of 2-D domains of anions and cations, stacked in an ..AABBAABB.. manner where the anionic sheets are constructed around the carboxylic-carboxylate supramolecular connector.