Quaternary cerium(iv) containing fluorides exhibiting Ce3F16 sheets and Ce6F30 frameworks

Abstract

A series of new Ce(IV) based fluorides with two different compositions, Cs₂MCe₃F₁₆ (M = Ni²⁺, Co²⁺, Mn²⁺, and Zn²⁺) and Na₃MCe₆F₃₀ (M = Al³⁺, Ga³⁺, Fe³⁺, and Cr³⁺) were synthesized as high quality single crystals via a mild hydrothermal route. The compounds with the composition Cs₂MCe₃F₁₆ (M = Ni²⁺, Co²⁺, Mn²⁺, and Zn²⁺) crystallize in the hexagonal crystal system with space group P6₃/mmc and are isotypic with the uranium analogs, whereas the Na₃MCe₆F₃₀ (M = Al³⁺, Ga³⁺, Fe³⁺, and Cr³⁺) compounds crystallize in the trigonal space group Pc1 and are isotypic with the uranium and thorium analogs Na_xMM′₆F₃₀ (M′ = Th, U). The Cs₂MCe₃F₁₆ compounds exhibit a complex 3D crystal structure constructed of edge-sharing cerium trimers, in which all three Ce atoms share a common μ₃-F unit. The Na₃MCe₆F₃₀ compounds are constructed of edge- and vertex-sharing cerium polyhedra connected to each other to form Ce₆F₃₀⁶⁻ framework, which can accommodate only relatively smaller trivalent cations (M³⁺ = Al³⁺, Ga³⁺, Fe³⁺, and Cr³⁺) as compared to uranium and thorium analogs. Magnetic susceptibility measurements were carried out on the samples of Cs₂MCe₃F₁₆ (M = Ni²⁺ and Co²⁺), which exhibit paramagnetic behavior.