Organic-inorganic hybrid iodobismuthate, [Bi(L)4(H2O)]Bi3I12, based on tris(2-pyridyl)phosphine oxide (L): Synthesis, structure and air-oxidation into [Bi(L)4]2[Bi4I16(I3)2]

Equimolar reaction of BiI3 with tris(2-pyridyl)phosphine oxide (L) (DMF, rt., 10 min) leads to unexpected formation of organic-inorganic hybrid iodobismuthate, [Bi(L)(4)(H2O)]Bi3I12 (1), isolated as solvate 1.3DMF in 90% yield. In the cation of latter, the Bi3+ ions is chelated by four ligand molecules in N,O-bidentate manner. The [Bi3I12](3)- anion features a linear structure of trans-configuration. The optical band gap being 2.08 eV indicates 1 as a promising light-harvesting material for dye-sensitized solar cells. Upon air-storage of 1 in CHCl3 solution, its [Bi3I12](3-) anion is converted into [Bi4I16](4-), [I-3](-) and I-2, which have been found in the structure of precipitated complex {[Bi(L)(4)](2)(Bi4I16)(I-3)(2)}center dot 1.5I(2)center dot 1.5H(2)O.