RbAuUSe3, CsAuUSe3, RbAuUTe3, and CsAuUTe3: Syntheses and structure; magnetic properties of RbAuUSe3

The compounds RbAuUSe3, CsAuUSe3, and RbAuUTe3 were synthesized at 1073K from the reactions of U, Au, Q, and A(2)Q(3) (A = Rb or Cs; Q Se or Te). The compound CsAuUTe3 was synthesized at 1173K from the reaction of U, Au, Te, and CsCl as a flux. These isostructural compounds crystallize in the KCuZrS3 structure type in space group Cmcm of the orthorhombic system. The structure consists of 2(infinity) [AuUQ(3)(-)] layers that contain nearly regular UQ(6) octahedra and distorted AuQ(4) tetrahedra. The infinite layers are separated by bicapped trigonal prismatic A cations. The magnetic behavior of RbAuUSe3 deviates significantly from Curie - Weiss behavior at low temperatures. For T>4200K, the values of the Curie constant C and the Weiss constant theta(p) are 1.82(9) emuK mol(-1) and -3.5(2) x 10(2)K, respectively. The effective magnetic moment mu(eff) is 3.81(9) mu(B). Formal oxidation statesof A/Au/U/Q may be assigned as +1/+1/+4/-2, respectively. (C) 2009 Elsevier Inc. All rights reserved.