Semiconducting [(Bi4te4br2)(Al2cl6-Xbrx)]Cl-2 And [Bi2se2br](Alcl4): Cationic Chalcogenide Frameworks From Lewis Acidic Ionic Liquids

Lewis acidic organic ionic liquids provide a novel synthetic medium to prepare new semiconducting chalcogenides, [(Bi4Te4Br2)(Al2Cl5.46Br0.54)]Cl-2 (1) and [Bi2Se2Br](AlCl4) (2). Compound 1 features a cationic [(Bi4Te4Br2)(Al2Cl5.46Br0.54)](2+) three-dimensional framework, while compound 2 consists of cationic layers of [Bi2Se2Br](2+). Spectroscopically measured band gaps of 1 and 2 are similar to 0.6 and similar to 1.2 eV, respectively. Thermoelectric power measurements of single crystals of 1 indicate an n-type semiconductor.