Crystal structure and magnetic properties of Cu3(TeO3)2Br2—a layered compound with a new Cu(II) coordination polyhedron

The new compound Cu3(TeO3)2Br2 crystallizes in the monoclinic spacegroup image. The unit cell parameters are image, image, image, image, image. The structure is solved from single crystal data, image. The new compound shows a layered structure where only weak van der Waals interactions connect the layers. There are two crystallographically different Cu(II) atoms; one having a square planar [CuO4] coordination and one showing an unusual [CuO4Br] trigonal bi-pyramidal coordination, the Br-ion is located in the equatorial plane. The Te(IV) atom has a tetrahedral [TeO3E] coordination where image is the image lone-pair. Within the layers the Cu-polyhedra are connected by corner- and edge sharing to form chains. The chains are separated by the Te atoms. The magnetic properties are dominated by long range magnetic ordering at image. Evidence for a coexistence of ferromagnetic and antiferromagnetic interactions exists.