Coordination Assemblies of CoII/CuII/ZnII/CdII with 2,5-Bipyridyl-1,3,4-Oxadiazole and Dicyanamide Anion: Structural Diversification and Properties

This work presents eight coordination assemblies based on divalent metal ions (M = Co-II, Cu-II, Zn-II, and Cd-II), dicyanamide anion (N(CN)(2)(-), dca), and two isomeric bent dipyridyl coligands (L), namely, 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo). In the resulting crystalline materials, both bpo and dca tectons generally display the bidentate bridging fashion (except in the mononuclear species 5), extending the metal centers to afford diverse one-, two-, and three-dimensional (1-D, 2-D, and 3-D) coordination networks that are not commonly observed in M-dca-L systems. Notably, the inclined polycatenated 2-D --> 3-D framework and 3-D polyknotting network with the unique 6-connected (4(4).6(11)) topology are formed for the Cu-II and Cd-II species with dca and 4-bpo. For the polymeric Co-II and Cu-II complexes, very weak anti ferromagnetic or ferromagnetic interactions are observed between the metal centers due to the mu(1,5)-bridging mode of dca, and their magneto-structural correlations have been discussed in detail. The Zn-II and Cd-II complexes show solid-state fluorescent emissions at room temperature.