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Abstract:
Sb2S3 and CuCl were reacted in the ionic liquid [BMIm]Cl center dot 4.4AlCl(3) (BMIm = 1-n-butyl-3-methylimidazolium) at 200 C. Upon cooling to room temperature, orange-red colored, air-sensitive crystals of Cu(Sb2S3)[AlCl4] precipitated. X-ray diffraction on a single-crystal revealed an orthorhombic crystal structure, in which cationic [Cu(Sb2S3)](+) layers are separated by tetrahedral [AlCl4](-) anions. The uncharged SiD2S3 partial structure consists of one-dimensional strands with covalent Sb-S single bonds. The copper(I) cation is coordinated by three sulfur atoms and by one of chlorine atoms of the [AlCl4](-) anion. An optical band gap of 2.14 eV was deduced from UV/Vis spectra. In very good agreement, a band gap of 2.07 eV results from DFT-based calculations involving a new implementation of the bifunctional formalism for the exchange energy. By treatment with 0.1 molar hydrochloric acid, AlCl3 was leached from Cu(Sb2S3)[AlCl4] yielding a compound with the presumed composition Cu(Sb2S3)Cl. Hydrolysis at higher pH resulted in Cu2-xS and Sb4O5Cl2.
