Significant Positional Isomeric Effect on Structural Assemblies of Zn(II) and Cd(II) Coordination Polymers Based on Bromoisophthalic Acids and Various Dipyridyl-Type Coligands

Seven Zn(II) and Cd(II) coordination polymers, formulated as {[Zn-2(5-Br-ip)(2)(bpy)(H2O)]center dot 2H(2)O}(n) (1), {[Zn(5-Br-ip)(bpa)(H2O)]}(n) (2), {[Cd(5-Br-ip)(bpp)(H2O)]}(n) (3), {[Zn(5-Br-ip)(bpe)]}(n) (4), {[Zn-2(4-Br-ip)(2)(bpy)]center dot H2O} (5), {[Zn(4-Br-ip)(bpa)(H2O)]}(n) (6), and {[Cd(4-Br-ip)(bpp)]} (7), were prepared by hydrothermal reactions based on 4-bromo- or 5-bromo-isophtlialic acid (4-Br-H(2)ip or 5-Br-H(2)ip) and different dipyridyl-type coligands 4,4'-bipyridyl (bpy), 1,2-bi(4-pyridyl)ethane (bpa), 1,3-di(4-pyridyl)propane (bpp), and 1,2-di(4-pyridyl)ethene (bpe). All complexes 1-7 were characterized by elemental analysis, IR spectra, and X-ray single-crystal diffraction. Complex 1 is a 2D (6,3) coordination network and further assembled into a 3D framework via pi-pi. stacking interactions. Complex 2 shows a 1D coordination array and further forms a 2D supra-molecular network via H-bonding interactions. Complex 3 has a 2-fold interpenetrating 3D diamond framework. Complex 4 is a 3-fold interpenetrating 3D network with CdSO4 topology, constructed from alternately left- and right-handed helical arrays. Complex 5 has a 3D (3,4)-connected network with (4 82)(4.8(2).10(3)) topology. Complex 6 features a I D coordination chain and further forms a 2D helical supramolecular pattern by H-bonding. Complex 7 exhibits a (3,5)-connected 2D layer with the Schlafli symbol of (4(2).6) (4(2).6(7).8). The results reveal that the diverse coordination networks of 1-7 can be adjusted by the different dispositions of the -Br substituent of isophthalate building blocks, as well as the metal ions and the dipyridyl coligands. Moreover, the luminescent properties of the complexes have been investigated.