Direct synthesis from various tetraphosphonic building blocks of homologuos hybrid-layered copper(II) derivatives incorporating copper hydrate cations

The solvothermal reaction of three different diamino tetraphosphonic acids of general formula (H2O3PCH2)(2)N-R-N(CH2PO3H2)(2), R = C6H12 (H8L1), 1,4-(CH2)(2)C6H4 (H8L2), and 1,3-(CH2)(2)C6H4 (H8L3), with copper acetate has led to three new layered copper phosphonates with similar structures. The three building blocks contribute to the formation of hybrid inorganic/organic anionic layers constituted of parallel polymeric inorganic units belonging to the layers and spaced by the organic linkers. The formers are built of copper square pyramids and tetrahedral phosphonic groups. The negative charge of the layers is compensated by unusual hexaaqua copper(II) cations placed into the interlayer region and linked to the layers by means of a complicated H-bonds network between water molecules and CPO3 groups in the sheets. Compounds I and 2 are isotypical and have the general formula Cu-2(H2O)(2)(H2L1)center dot Cu(H2O)(6 center dot)2H(2)O and Cu-2(H2O)(2)(H2L2)center dot Cu(H2O)(6)center dot 2H(2)O, respectively. In contrast, in compound 3, with the formula Cu-2(H2O)(2)(H2L3)center dot Cu(H2O)(3)center dot 3H(2)O, the interlayer copper ions are three-hydrated and are directly connected to the deprotonated PO groups. The structures of compounds I and 3 have been solved from X-ray single-crystal diffraction data, whereas the structure of compound 2 has been refined from X-ray powder diffraction data using a model derived from that of 1. The thermal and magnetic properties of these compounds have been investigated by means of several techniques.