Multinary Halogenido Bismuthates beyond the Double Perovskite Motif.

ABSTRACT

Both lead halide perovskites and bismuth-based double perovskites have generated intense research interest in the past few years. There is, however, a broader class of bismuthates that transcends the double perovskite motif. These multinary halogenido bismuthates remain severely underexplored and offer rich research opportunities with regard to new structure motifs and material properties. In this Forum Article, we want to provide both an overview of the work on this class of compounds that has been done in the last 2 decades and an example of how new compounds can be obtained and which challenges are associated with their synthesis. We present the synthesis and characterization of six new bismuthates, (PBz4)3Bi3Br12 (1) (PBz4)2(MeCN)2Cu2Bi2Br10 (2), (PBz4)Bi2I7 (3), (PBz4)2(MeCN)2Cu2Bi2I10 (4), (PBz4)2AgBi2I9 (5), and (PBz4)3Bi3I12·C4H8O (6), based on the tetrabenzylphosphonium cation PBz4+. 2, 4, and 5 represent new multinary bismuthates, featuring both a familiar anion motif with a new element combination in 2 and a previously unknown anionic chain in 5. We use this series of compounds to further elucidate the influence of the anion composition, nuclearity, and dimensionality on the compounds' onset of absorption and discover that an additional factor, the connectivity between coordination polyhedra, plays a role in copper iodido bismuthates.