Crystal Structure and Optical Properties of New Hybrid Halobismuthates of 2,2'-Bipyridinium Derivatives

New hybrid 2,2'-bipyridinium halobismuthates ([bipyH]+) (I and II), 7,8-dihydro-6H-dipyrido[1,2-a:2',1'-c][1,4]diazepine-5,9-diium ([bipyC3]2+) (III), 6,7,8,9-tetrahydrodipyrido[1,2-a:2',1'-c][1,4]diazocin-5,10-diium ([bipyC4]2+) (IV), and 1,1'-(pentanediyl)bis(2,2'-bipyridinium) ((bipyH)2C5]4+) (V) have been isolated and characterized by X-ray diffraction. The structure of I contains a monoprotonated cation 2,2'-bipyridinium and the isolated [Bi2Br10]4– anion. 2,2'-Bipyridinium bromobismuthate II contains a polymeric anion and is isostructural to the previously described iodobismuthate. Bromobismuthate III includes [BiBr6]3– anions and water molecules. Iodobismuthate [bipyC3]2[Bi2I10] (VI) is isostructural to IV. The structure of V contains [(bipyH)2C5]4+ cations and three types of anions: [Bi2Br10]4–, [BiBr6]3–, and Br–. Compounds I, III, and VI have been isolated in pure form. The values of the optical band gap for them are 2.84, 2.88, and 2.11 eV, respectively.