Synthesis, Crystal Structures and Fluorescent Properties of Two Bimetallic Coordination Polymers

Two novel 2D and 3D bimetallic (CdNiII)-Ni-II coordination polymers, Cd(2Mpz)(H2O)Ni(CN)(4) (I) (2Mpz: 2-methylpyrazine) and Cd(2Epz)(H2O)Ni(CN)(4) (II) (2Epz: 2-ethylpyrazine), have been synthesized and characterized by elemental analysis, powder X-ray diffraction, IR spectra, fluorescent spectra, single crystal X-ray diffraction and thermogravimetric analysis. Based on the analysis of structures, it can be found that the Cd(II) ions in the two complexes have the similar octahedral coordination geometry of CdN5O, which are linked by [Ni(CN)(4)](2-) units at the equatorial plane to form 2D sheet layers [CdNi(CN)(4)] (n) . However, it's noted that the coordination environment of Ni(II) ions and action of ligands are different. All the Ni(II) ions in I are the five-coordinated pentahedron configuration and 2-methylpyrazine acts as a bridging ligand linking the Cd(II) and Ni(II) ions of the adjacent layers, leading to the 3D metal-organic framework. The structure of II indicates all the Ni(II) ions are the four-coordinated square plane and 2-ethylpyrazine is a terminal ligand coordinated to Cd(II) ions, forming the 2D layer structure. Moreover, the two complexes display significant thermal stability and fluorescent properties.