Copper diphosphonates with zero-, one- and two-dimensional structures:: ferrimagnetism in layer compound Cu3(ImhedpH)2•2H2O [ImhedpH4 = (1-C3H3N2)CH2C(OH)(PO3H2)2]

Reactions of CuSO(4) with 2-(1-imidazole)-1-hydroxy-1,1'-ethylidenediphosphonic acid (ImhedpH(4)) under hydrothermal conditions at different temperatures lead to four new metal phosphonates: Cu(ImhedpH(3))(2)(H(2)O)center dot 2H(2)O (1), Cu(ImhedpH(3))(2) (2), Cu(3)(ImhedpH(2))(2)(ImhedpH(3))(2)center dot 4H(2)O(3), and Cu(3)(ImhedpH)(2)center dot 2H(2)O (4). Compounds 1 and 2 have mononuclear structures in which the Cu atoms adopt square pyramidal and square planar geometries, respectively. In compound 3, a chain structure is observed where the Cu(3)(ImhedpH(2))(2)(ImhedpH(3))(2) trimer units are connected by edge-sharing of the Cu(2)O(5)} square pyramids. Compound 4 exhibits a layer structure made up of Cu3( ImhedpH)(2) trimer units. The connection of trimers through corner-sharing of {Cu(1)O(4)} and {CPO(3)} tetrahedra results in a two-dimensional layer containing 8- and 16-membered rings. The imidazole groups are grafted on the two sides of the layer. Magnetic studies reveal that ferromagnetic interactions are mediated in 3, while for compound 4, ferrimagnetism is observed below 5.8 K.