Syntheses, structures, and properties of honeycomb and square grid coordination polymers with in situ formed 5-(2′-pyrimidyl)tetrazolate

Solvothermal reactions of Zn(II), Cd(II), Mn(II), Co(II), or Ni(II) salts and 2-pyrimidinecarbonitrile (pymCN) in the presence of NaN₃ in DMF yielded seven metal-organic coordination polymers formulated as [Zn(pymtz) ₂]_n (1), [NaM^II(pymtz)₃]_n ·G (M = Zn 2, Cd 3, Mn 4, Co for 5, and Ni for 6; G = DMF and/or H ₂O) and [Cd(pymtz)₂]_n (7) [pymtz = 5-(2′-pyrimidyl)tetrazolato]. Compounds 2-6 are isomorphous and all contain neutral honeycomb layers in which pymtz serves as a bis(chelating) bridge between M(II) (M = Zn for 2, Cd for 3, Mn for 4, Co for 5, and Ni for 6) and Na⁺, and the ellipse stacking of the layers generates one-dimensional hexagonal channels. Compounds 1 and 7 exhibit different (4,4) square grid networks. In 1, the Zn ions are octahedrally coordinated and linked by pymtz ligands in the μ₂ tridentate bridging mode, while in 7, the Cd(II) ions are eight-coordinated with a square prismatic geometry and bridged by bis(chelating) pymtz ligands. Compounds 2 and 3 can transform into 1 and 7, respectively, by immersing the sample in appropriate solvents. Interestingly, photoluminescence measurements on Zn(II) and Cd(II) compounds show that the emission bands can be correlated to the coordination modes of the pymtz ligands.