Hybrid halide materials consist of a cationic organic amine (A), a metal (M), and a halide (X). Some of these AMX₃ perovskites are interesting magnetic materials. AMX₃ perovskites and hybrid tin and lead halides have revolutionized solar cells by allowing their low-cost, simple production.

Ram Seshadri, Anthony Cheetham, and colleagues, University of California, Santa Barbara, USA, have synthesized a range of new methylammonium (MA) ruthenium halides. The compounds were prepared solvothermally starting from RuCl₃. Hypophosphorous acid was used to control the oxidation state of ruthenium. The three classes of compounds prepared, MA₂Ru^IVX₆, MA₂MRu^IIIX₆, and MA₃Ru^III₂Br₉ (M = Na, K, or Ag; X = Cl, Br; examples pictured), crystallize in different structures, as shown by single-crystal X-ray diffraction.

The compounds of the type MA₂RuX₆ (pictured left) crystallize in the trigonal space group R3m. The compounds of the type MA₂MRuX₆ (pictured center) crystallize in a structure related to BaNiO₃, with alternating MX₆ and RuX₆ octahedra forming chains in the trigonal P3m space group. The compound MA₃Ru₂Br₉ (pictured right) crystallizes in the orthorhombic Cmcm space group and contains pairs of face‐sharing octahedra. The magnetic behavior of all three classes of compounds is influenced by spin-orbit coupling, and the effective magnetic moments of the compounds decrease in the order MA₂RuX₆ > MA₂MRuX₆ > MA₃Ru₂Br₉.

• Structural Diversity and Magnetic Properties of Hybrid Ruthenium Halide Perovskites and Related Compounds,
  Pratap Vishnoi, Julia L. Zuo, T. Amanda Strom, Guang Wu, Stephen D. Wilson, Ram Seshadri, Anthony K. Cheetham,
  Angew. Chem. Int. Ed. 2020.
  https://doi.org/10.1002/anie.202003095