Syntheses, structures, thermal stabilities and magnetic properties of two-layered metal diphosphonates

Hydrothermal reactions of Cu-II or Ni-II with risedronic acid (H(4)Ris) in the presence of organic amine afforded two-layered metal phosphonates with different types of structures, namely [Cu-2(HRis)]center dot(H2O)center dot 0.5(NH2CH2CH2NH2) (1) and [Ni(HRis)(2)](2){Ni(H2O)(2)}(2)]center dot H2O (2). In compound 1, the adjacent equivalent [Cu1O(5)] square pyramids are linked by two mu(2)-O atoms into an edge-sharing {Cu-2(mu(2)-O)(2)} dimer. These dimers are linked together by four {PCO3} tetrahedra, leading to an inorganic chain. The adjacent chains are further connected by Cu atoms through the phosphonate oxygen atoms from one chain and one pyridyl nitrogen atom (N1) from the other chain to give an organic-inorganic layer. In compound 2, the Ni is connected by O-P-O units into a chain structure, which is further connected by {NiO6} octahedra into a double-chain structure. Neighboring double chains are linked by HRis(3-) ligands into a layered structure. Magnetic susceptibility measurements indicate that antiferromagnetic interactions dominate in both complexes.