The novel title organic salt, 4C5H7N2(+)·C24H8O8(4-)·8H2O, was obtained from the reaction of perylene-3,4,9,10-tetracarboxylic acid (H4ptca) with 4-aminopyridine (4-ap). The asymmetric unit contains half a perylene-3,4,9,10-tetracarboxylate (ptca(4-)) anion with twofold symmetry, two 4-aminopyridinium (4-Hap(+)) cations and four water molecules. Strong N-H···O hydrogen bonds connect each ptca(4-) anion with four 4-Hap(+) cations to form a one-dimensional linear chain along the [010] direction, decorated by additional 4-Hap(+) cations attached by weak N-H···O hydrogen bonds to the ptca(4-) anions. Intermolecular O-H···O interactions of water molecules with ptca(4-) and 4-Hap(+) ions complete the three-dimensional hydrogen-bonding network. From the viewpoint of topology, each ptca(4-) anion acts as a 16-connected node by hydrogen bonding to six 4-Hap(+) cations and ten water molecules to yield a highly connected hydrogen-bonding framework. π-π interactions between 4-Hap(+) cations, and between 4-Hap(+) cations and ptca(4-) anions, further stabilize the three-dimensional hydrogen-bonding network.
Keywords: TOPOS topology; charge-assisted hydrogen bonds; condensed benzenoid hydrocarbons; crystal structure; highly connected networks; organic salt.