Novel coordination frameworks incorporating the 4,4’-bipyrazolyl ditopic ligand

The reaction of the rigid spacer 4,4′-bipyrazole (H2BPZ) with late transition metals, either following conventional routes or under solvothermal conditions, afforded the coordination polymers [M(BPZ)]·Solv (M = Zn,1; Co, 2; Cd, 3; Hg, 4; Cu,5; Ni, 6; Pd, 7; Solv = DMF, 3; MeCN, 5 and 6; H2O, 7), [Cu(H2BPZ)2(NO3)2 ](8), and [Cd(H2BPZ)(CH3COO)2] (9). State-of-the-art laboratory powder diffraction methods allowed to disclose the isomorphous character of 1 and 2 , as well as of 5 and 6, which feature 3D porous networks containing 1D channels of square and rhombic shape, respectively. 3, crystallizing in the relatively rare P6122 space group, consists of homochiral helices of octahedral Cd(II) ions, packing in bundles mutually linked by “radial”, nonplanar BPZ(2-) ligands. Finally, the dense species 8 and 9 contain parallel 2D layers of square and rectangular meshes, respectively. Thermogravimetric analyses witnessed the relevant thermal robustness of all the [M(BPZ)] materials [except the mercury(II) derivative], which are stable in air at least up to 300°C, with the zinc(II) derivative decomposing only around 450 °C. Variable-temperature powder diffraction experiments highlighted the permanent porosity of 1−3, 5, and 6, retained along consecutive temperature cycles in all cases but3. When probed with N2 at 77 K,1−3 and 5−7 showed Brunauer−Emmett− Teller and Langmuir specific surface areas in the ranges 314(2)−993(11) and 509(16)−1105(1) m2/g, respectively.