A series of coordination polymers constructed by a flexible tetracarboxylic acid: synthesis, structural diversity and luminescent properties

Abstract

By using a flexible tetracarboxylic acid ligand, 5,5′-(p-xylylenediamino)-1,1′,3,3′-(benzene-tetra-carboxylic acid) (H4L), and three N-donor rigid co-ligands, ten coordination polymers, [Cu(4bipy)2](H2L) (1), [Cd2(L)(2bipy)2]·5H2O (2), [Cd2(L)(H2O)6]·2H2O (3), [Mn2(L)(H2O)6]·4H2O (4), [Co2(L)(H2O)6]·4H2O (5), [Zn2(L)(2bipy)2]·3H2O (6), [Zn2(L)(phen)2]·2H2O (7), [Ni2(L)(2bipy)2(H2O)2]·2H2O (8), and [Cu2(L)(phen)2(H2O)2] (9), and [Zn2(L)(phen)2(H2O)2] (10) (4bipy = 4,4′-bipyridine, 2bipy = 2,2′-bipyridine, and phen = 1,10-phenanthroline) have been synthesized and structurally characterized by elemental analysis, IR, single-crystal X-ray diffraction and thermogravimetric analysis. The single crystal of ligand H4L reveals that there are two pairs of hydrogen bonds between two H4L molecules, which lead to a 1-D linear supramolecular chain. Complex 1 shows a three-dimensional (3D) two-fold interpenetrated Cu2+-4bipy cationic host framework, [Cu(4bipy)2]2+ with the 4-connected dia net, in which there are 1-D guest supramolecular chains formed by the intermolecular hydrogen bonds between adjacent (H2L)2− anions. 2 has a two-dimensional (2D) 4-connected {44·62} uninodal sql/Shubnikov tetragonal plane network. 3–10 display a new 2D 2-nodal (2,4)-connected network with a {84·122}{8}2 topology. Complexes 3–5, 9 and 10 generate a 3D supramolecular structure by the hydrogen bonds between adjacent layers. 6–8 form a 3D network through strong π⋯π stacking interactions between adjacent layers. The co-ligand effects on the complex structures are studied. Also, we investigate the solid-state luminescence of compounds H4L, 2–10 at room temperature.