New 3D Coordination Polymers Constructed from Pillared Metal-Formate Kagome Layers Exhibiting Spin Canting Only in the Nickel(II) Complex

Sparked by the strategy of pillared-layer MOFs, three formate coordination polymers, {[Ni-2(HCO2)(3)(L)(2)](NO3)center dot 2H(2)O}(infinity) (1), {[Co-2(HCO2)(3)(L)(2)](HCO2)center dot 2H(2)O}(infinity) (2), and {[Cu-2(HCO2)(3)(L)(2)](HCO2)center dot 2H(2)O}(infinity) (3), have been synthesized by employing the rodlike ligand 4,4'-bis(imidazol-1-yl)biphenyl (L) as the pillar. Structural analysis indicates that the title complexes 1-3 are iscistructural compounds, which possess metal-formate 2D layers perpendicularly pillared by the ligand L to afford a 3D open framework. This is an interesting example of a Kagome lattice based on the formate mediator. Moreover, the formate anion of this 2D Kagome layer exhibits various bridging modes anti-anti, syn-anti, and 321 modes. Their magnetic measurements reveals that only complex 1 presents the spin canting phenomenon, while its isostructural Co-II and Cu-II complexes are simply paramagnets with antiferromagnetic coupling.