A new class of hybrid materials via salt inclusion:: Novel copper(II) arsenates Na5ACu4(AsO4)4Cl2 (A = Rb, Cs) composed of alternating covalent and ionic lattices

Two novel copper(II) arsenates Na5ACu4(AsO4)4Cl2 (A = Rb, Cs) were synthesized by conventional solid-state methods using reactive molten salt media. These compounds are isostructural and crystallize in an orthorhombic lattice (Fmmm, No. 69; Z = 8). The cell constants are a = 14.632(3) Å, b = 18.872(2) Å, c = 14.445(3) Å, V = 3989(1) Å3, for A = Rb; a = 14.638(3) Å, b = 18.990(4) Å, c = 14.418(3) Å, V = 4008(1) Å3, for A = Cs. Single-crystal structure studies reveal a new composite framework consisting of alternating covalent and ionic lattices. The covalent lattice contains highly oriented oligomeric μ-oxo [Cu4O12]16- tetrameric units with a cyclo-S8-like Cu4O4 magnetic core that resembles the building block of layered cuprates. The ionic slab consists of a novel framework of mixed alkali metal chloride lattice and rarely seen Na6O8 clusters. Similar to organic-inorganic hybrid materials, the title compounds present a new class of host-guest chemistry via salt inclusion reactions. Copyright © 2002 American Chemical Society.