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

Sparked by the strategy of pillared-layer MOFs, three formate coordination polymers, {[Ni2(HCO2)3(L)2](NO3)·2H2O}∞ (1), {[Co2(HCO2)3(L)2](HCO2)·2H2O}∞ (2), and {[Cu2(HCO2)3(L)2](HCO2)·2H2O}∞ (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 isostructural 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 Kagomé lattice based on the formate mediator. Moreover, the formate anion of this 2D Kagomé layer exhibits various bridging modes: anti-anti, syn-anti, and 3.21 modes. Their magnetic measurements reveals that only complex 1 presents the spin canting phenomenon, while its isostructural CoII and CuII complexes are simply paramagnets with antiferromagnetic coupling.