Hydrothermal synthesis, crystal structure and magnetic properties of a novel nickel carboxylate–phosphonate with a layered structure

Hydrothermal reactions of N-(phosphonomethyl)proline (H3L) with nickel sulfate hexahydrate resulted in a novel nickel carboxylate–phosphonate: |H2O|[Ni3(O3PCH2–NC4H7–CO2)2(H2O)4] (complex 1). Single-crystal X-ray diffraction analysis revealed that complex 1 crystallizes in the triclinic space group P-1 (No. 2), with lattice parameters of a = 10.0167(5) Å, b = 10.3882(5) Å, c = 11.9528(5) Å, α = 90.132(3)°, β = 107.246(3)°, γ = 111.158(3)°, V = 1099.39(9) Å3, and Z = 2. Complex 1 features a 2D layered structure. The structure contains alternating Ni-centered octahedra (Ni(1)O6, Ni(2)O5N and Ni(3)O5N) and O3PC tetrahedra linked to construct a layer with rhombohedral 12-MRs holes. The cyclopentylamine moieties of H3L were grafted onto the layer through coordination of CPO3, CO2 and (CH2)2NCH2 with central nickel atoms. These layers are stacked in an AA sequence, which results in a one-dimensional channel in the [001] direction. Water molecules are located in these channels. Magnetic studies showed that complex 1 exhibits predominantly paramagnetic behavior.