Hybrid and Inorganic Vacancy-Ordered Double Perovskites A₂WCl₆

Abstract

We report hybrid and all-inorganic, vacancy-ordered double perovskites of d² W⁴⁺ with the formula A₂WCl₆ (A = CH₃NH₃⁺, Rb⁺, and Cs⁺). These compounds, which are reddish in color, can be distinguished from structurally similar compounds obtained by hydrothermal methods on the basis of structure, spectroscopic, and magnetic properties. The latter are green and incorporate oxygen, with the actual formula Cs₂WO_xCl_6–x and distinct optical absorption and emission behavior. Furthermore, the local-moment magnetism of the pure-red d² compounds reported here does not correspond to the appropriate Kotani model, suggesting as-yet undiscovered physics in these systems.