Na4Co3(PO4)(2)P2O7, a new sodium cobalt phosphate containing a three-dimensional system of large intersecting tunnels

Single crystals of the new Co(II) phosphate Na4Co3(PO4)(2)P2O7 have been isolated and their structure has been determined by X-ray diffraction techniques, This compound crystallizes in the orthorhombic noncentrosymmetric space group Pn2(1)a with a = 18.046(5) Angstrom, b = 6.533(2) Angstrom, c = 10.536(2) Angstrom, and Z = 4, The structure consists of infinite layers with composition (Co3P2O13)(infinity) parallel to the be plane, Interlayer linkages are made via P-O-P bridges of the pyrophosphate groups in such a way that large tunnels extending along the [010] and [001] directions occur between two neighboring sheets, Besides, there also exist channels along the [100] direction crossing the (Co3P2P13)(infinity) layers, A complex scheme of tunnel intersections gives rise to the formation of a three-dimensional channel network which hosts the sodium cations. (C) 1996 Academic Press, Inc.