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

Abstract

Reactions of CuSO₄ with 2-(1-imidazole)-1-hydroxy-1,1′-ethylidenediphosphonic acid (ImhedpH₄) under hydrothermal conditions at different temperatures lead to four new metal phosphonates: Cu(ImhedpH₃)₂(H₂O)·2H₂O (1), Cu(ImhedpH₃)₂ (2), Cu₃(ImhedpH₂)₂(ImhedpH₃)₂·4H₂O (3), and Cu₃(ImhedpH)₂·2H₂O (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 Cu₃(ImhedpH₂)₂(ImhedpH₃)₂ trimer units are connected by edge-sharing of the {Cu(2)O₅} 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)O₄} and {CPO₃} 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.