SYNTHESIS, CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF A NOVEL MIXED-VALENCE COPPER PHOSPHONATE - NA2CU15(HEDP)(6)(OH)(2)(H2O) (HEDP = 1-HYDROXYETHYLIDENEDIPHOSPHONATE)

A new pillared layered mixed-valence copper phosphonate Na2Cu15(hedp)( 6)(OH)(2)(H2O), where hedp represents 1-hydroxyethyldenediphosphonate anion, has been hydrothermally synthesized and structurally determined . Crystal data: trigonal, space group <P(3)over bar>, a = b = 11.720(2 ), c = 9.531(1) Angstrom, U = 1134(2) Angstrom(3), Z = 1. The structur e consists of honeycomb layers of edge-sharing ((Cu3O)-O-II)O-3 units (sheet A) and edge-sharing NaO6 octahedra and (CuO4)-O-II planes (shee t B). The layers are pillared alternately through 18-membered rings wh ich are made up from the organic backbone of the diphosphonate groups and the (CuO2)-O-II units. A three-dimensional framework is thus forme d which contains intersecting channels where the H2O molecules reside. The magnetic properties of the compound have been investigated. No lo ng-range ordering has been found down to 2 K.