In this work we synthesised four new pyridine acylamide complexes [HgI2(L1)] (1) and (2), [HgI2(L2)2] (3), and [HgI2(L3)]n (4) (L1 = N,N′-bis(3-pyridylmethyl)benzene-1,4-dicarboxamide, L2 = N4,N4′-bis(pyridin-3-yl)-[1,1′-biphenyl]-4,4′-dicarboxamide, L3 = N1,N3-bis(pyridin-3-ylmethyl)isophthalamide) by solvo(hydro)thermal reaction. Compounds 1 and 2 are supramolecular isomers prepared via variation of the reaction solvent, in which the HgII centres are bridged by L1 ligands to form one-dimensional (1D) helical chain or 1D meso-helical chain, respectively. Careful inspection of the structures reveal that formation of the isomers are mainly induced by the distinct configuration of L1 ligand and slight differences in coordination geometry of the HgII ions. Complex 3 shows a novel Z-shaped zero-dimensional structure with a L2–HgI2–L2–HgI2–L2 arrangement. In complex 4, flexible L3 ligands link HgI2 units to construct a 1D helical chain with an overall chiral structure, derived from spontaneous resolution. Luminescence properties of these four novel complexes were also explored.
Seven crystal structures of pyromellitic acid or trimesic acid salts of molecules that contain pyridine and amide functionalities were determined and their structures were analyzed in detail in terms of various intermolecular interactions. The presence of multiple functionalities (acid, pyridine, amide, and hydroxy groups) in these structures resulted in diversified supramolecular architectures. Amide-to-amide hydrogen bonds are not observed in any of these structures because of interference by the anions, water molecules, or pyridinium cations. The symmetry of the components was found to be important in determining the resultant supramolecular synthon and, therefore, the overall architecture. The pyromellitate anions exhibited four types of geometries which, differ in valencies and intramolecular hydrogen bonding, and these anions also exhibit self stacks when they have planar geometries.