Syntheses, Structures, and Luminescent Properties of Six New Zinc(II) Coordination Polymers Constructed by Flexible Tetracarboxylate and Various Pyridine Ligands

Under solvothermal
conditions, six new Zn­(II) coordination polymers,
[(CH3)2NH2]2[Zn­(L)]·2H2O (1), [Zn2(L)­(py)2] (2), [Zn2(L)­(bpe)2]·bpe·6H2O (3), [Zn2(L)­(bpe)­(DMA)­(H2O)]·5H2O (4), [Zn2(L)­(bpy)0.5(H2O)2]·2.5H2O (5), and [Zn2(L)­(bpe)­(H2O)]·3H2O (6) [H4L = 5,5′-(p-xylylenediamino)-1,1′,3,3′-(benzenetetra-carboxylic
acid), py = pyridine, bpy = 4,4′-dipyridine and bpe = 1,2-bis­(4-pyridyl)­ethane],
have been synthesized by employing a flexible tetracarboxylic acid
H4L and different auxiliary pyridine-based ligands. In 1–6, all L4– ligands
are 4-connected nodes; however, the diverse configurations of the
two terminal isophthalate units of L4– around the
central −NHCH2PhCH2NH– spacer
lead to various topological nets. 1 shows a three-dimensional
(3D) 2-fold interpenetrated 4-connected dia network resulting
from the vertical configuration of the two isophthalate units of L4–. 2 displays a 3D (4,4)-connected pts net in which the two isophthalate units of L4– adopt a parallel configuration. The two isophthalate units of L4– in 3 are also almost parallel, resulting
in an intriguing 3D 2-fold interpenetrated network with the (4,4)-connected bbf net. 4 is a two-dimensional bilayer structure,
extending into a 3D supramolecular framework through interlayer hydrogen-bonding
interactions. 5 and 6 disclose similar 3D
structural architectures, in which the two isophthalate units of L4– are almost vertical and exhibit tetrahedral topological
nodes, inducing a rare (4,5)-connected xww net and an
unprecedented (4,6)-connected network, respectively. The thermal stabilities
and luminescent properties of 1–6 have also been studied in detail. The complexes exhibit intense
solid-state fluorescent emissions at room temperature.