Ab initio crystal structure of nickel(II) hydroxy-terephthalate by synchrotron powder diffraction and magnetic study

The structure of the new hybrid compound [Ni3(OH)2(tp)2(H2O)4]·2H2O (tp = C8H4O42−) has been determined ab initio from synchrotron powder diffraction data and refined with the Rietveld method: space group P-1, a = 10.2077(6) Å, b = 8.0135(5) Å, c = 6.3337(4) Å, α = 97.70 (1)°, β = 97.21(1)°, γ = 108.77(1)°, Dx = 2.124 g/cm3, Rp = 0.045, RB = 0.095 (757 independent reflections). H atoms were placed geometrically and their position optimized by DFT calculation. The repeating structural unit is the chain [Ni(1)O6]2Ni(2)O6, consisting of two edges sharing octahedrons related by the symmetry center and linked via μ3-OH to a vertex of Ni(2) octahedron. The Ni(1) coordination is ensured by two oxygen atoms from two water molecules, two OH and two oxygen atoms from carboxylate groups. The linkage of the chains by the tp anions forms infinite layers parallel to the (010) planes. Interchain hydrogen bonds between the water molecules coordinating the metal ensure the cohesion of the 2D structure. The structural and magnetic properties are compared with that of the 3D fumarate-based compound [Ni3(OH)2(fum)2(H2O)4]·2H2O (fum = C4H2O42−).