Hydrothermal syntheses, crystal structures and properties of three new zinc(II) coordination polymers with in situ formed 5-(3-pyridyl)tetrazolate

The synthesis of three new zinc coordination polymers, [Zn(3-pttz)2(4,4ʹ-bipy)] (1), [Zn(3-pttz)(TPA)(H2O)2] (2) and [Zn(3-pttz)(PMA)0.5] (3) (3-pttz = 5-(3-pyridyl)tetrazolate, TPA = terephthalic acid and PMA = 1,2,4,5-Benzenetetracarboxylic acid), with sodium azide and 3-cyanopyridine via in situ hydrothermal method have been investigated. These three coordination polymers were successfully synthesized, and characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, thermal studies and single-crystal X-ray diffraction. The results indicate that in compound 1, the 3-pttz ligands adopt monodentate coordination mode while the 4,4ʹ-bipy ligands bridge the Zn(II) ions to generate infinite − Zn − 4,4ʹ-bipy − Zn − chains, which furthermore through weak C-H···N hydrogen bonds to form a three-dimensional (3D) supermolecular structure. For compound 2, the Zn(II) ions are connected by 3-pttz ligands to form one-dimension (1D) − 3-pttz − Zn − 3-pttz − helical chains, and the secondary ligands TPA adopt the terminal mode; the chains are assembled into a 3D supermolecular framework via hydrogen bonds. Compound 3 is a two-dimensional (2D) network constructed from self-assembly of Zn (II) ions and PMA ligands with the 3-pttz ligands by assuming the monodentate coordination mode, resulting in the formation of a 3D supermolecular framework via weak C-H···O hydrogen bonds. Furthermore, thermal behaviors and luminescence properties for these crystalline materials have been investigated.