A new layered potassium-based molybdenum-tungsten monophosphate: synthesis, crystal structure, XPS and magnetic studies

A new compound, K-5[(Mo3.2W1.8)O-11](PO4)(3)[(P0.5Mo0.5)O-4], was synthesized via solid-state reaction and its crystal structure was determined by single-crystal X-ray diffraction. This compound crystallizes in the space group Pnma, with a = 9.0360(4) angstrom, b = 10.1603(4) angstrom, c = 26.1538(12) angstrom and V = 2401.14(18) angstrom(3). The structure consists of a corner-sharing MO6-TO4 (M = Mo, W; T = P, Mo) polyhedral connection arranged to form an ordered packing of similar to 14.9 angstrom-thick layers parallel to (001). The stacking of the layers forms trigonal, tetragonal and hexagonal channels. XPS study reveals the presence of W at the hexavalent state only, whereas Mo appears as a mixed-valent species (Mo6+, Mo5+ and Mo4+). Magnetic susceptibility reveals the occurrence of a relevant antiferromagnetic coupling and is consistent with the presence of reduced metal species as indicated by the XPS results.