One-Dimensional Diiodine-Iodobismuthate(III) Hybrids Cat3{[Bi2I9](I2)3}: Syntheses, Stability, and Optical Properties

One-dimensional iodine-rich iodobismuthates(III), Cat(3){[Bi2I9](I-2)(3)} [Cat = 1,4-MePy (1) and 1-EtBMAP (2)], feature the highest amount of trapped diiodine units in polyhalogen-halometalates of p-block elements. Both complexes have narrow optical band gaps (1.55 and 1.63 eV, respectively) and moderate thermal stability.