Perovskite-related hybrid noble metal iodides: Formamidinium platinum iodide [(FA)2PtIVI6] and mixed-valence methylammonium gold iodide [(MA)2AuIAuIIII6].

Noble metal halide compounds are an exciting class of materials which display unique crystal chemistry with temperature and pressure. Here we report two new compounds, single-valence formamidinium platinum iodide [(FA) 2 Pt IV I 6 ] and mixed-valence methylammonium gold iodide [(MA) 2 Au I Au III I 6 ]. Structural changes between 300 K and 100 K have been monitored. The compounds crystallize in two different perovskite-related structure classes, with the added complexity of a disordered, “tumbling”, organic cation at 300 K. This tumbling is significantly reduced at 100 K. (FA) 2 Pt IV I 6 undergoes in-phase octahedral tilting similar to related vacancy-ordered perovskite materials. At 100 K, (MA) 2 Au I Au III I 6 undergoes a transition which facilitates stronger Au–I covalent bonding as made evident by a contraction of the unit cell and distances between Au and I atoms in the ab plane. [ABSTRACT FROM AUTHOR]