Cadmium(II) and zinc(II) coordination polymers with mixed building blocks of benzenedicarboxyl and 2,5-bipyridyl-1,3,4-oxadiazole: Syntheses, crystal structures, and properties

Three Cd(II) and Zn(II) coordination polymers, including {[Cd(3-bpo)(mip)(H2O)](H2O)2}n (1), {[Cd(4-bpo)(hip)(H2O)](H2O)4}n (2), and {[Zn(4-bpo)(tp)](CH3OH)}n (3) were synthesized from the reactions of CdII or ZnII nitrate with mixed organic ligands [3-bpo = 2,5-bis(3-pyridyl)-1,3,4-oxadiazole, H2mip = 5-methylisophthalic acid, 4-bpo = 2,5-bis(4-pyridyl)-1,3,4-oxadiazole, H2hip = 5-hydroxylisophthalic acid, H2tp = terephthalic acid] under the similar layered diffusion condition. The resulting crystalline materials 1–3 were characterized by IR, microanalysis, powder X-ray diffraction (PXRD) techniques. Single-crystal X-ray diffraction indicates a 1-D tubular motif for 1, a 1-D dual-track array for 2, and a 2-D grid-like pattern for 3, constructed via different metal–ligand coordination contacts. Higher-dimensional supramolecular architectures are further assembled in 1–3 via H-bonding and aromatic stacking interactions. In addition, thermal stability and fluorescence of these polymeric complexes were also investigated and discussed.

Graphical abstractThis work presents three CdII and ZnII coordination polymers based on mixed organic ligands, including 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and its 4-pyridyl analog (4-bpo), as well as 5-methylisophthalate (mip), 5-hydroxylisophthalate (hip), and terephthalate (tp), which display various 1-D tubular motif, 1-D dual-track array, and 2-D latticework, respectively, in virtue of metal–ligands coordination.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► CdII and ZnII coordination polymers. ► Mixed ligands including benzenedicarboxylicate and 2,5-bipyridyl-1,3,4-oxadiazole. ► Secondary interactions facilitate higher-dimensional supramolecular structures. ► Thermal stability and fluorescence property.