Structural, vibrational and optical properties of a new self assembled organic-inorganic nanowire crystal (C6H14N)2[BiBr5]. A Density Functional Theory approach

Single crystal and thin films of a new organic-inorganic hybrid material (C6H14N)2[BiBr5] were synthesized by the slow evaporation method at room temperature and characterized by X-ray diffraction, Raman spectroscopy, optical absorption and photoluminescence measurements. The crystal structure was determined in the monoclinic system with P21/c space group. The structure is built up from BiBr6 octahedra sharing two cis-bromine atoms and forming infinite [BiBr5]n zig-zag chains surrounded by organic cations. Such a one-dimensional (1D) structure may be regarded as quantum wires system in which the [BiBr5]n inorganic chains act as semiconductor wires and the (C6H14N) organic cations act as insulator barriers. The cohesion of the structure is achieved by an extensive network of N-H…Br hydrogen bonds. The Raman and Infrared spectra where interpreted by analogy with the homologous materials and by calculation of normal mode frequencies using the density functional theory (DFT) method. The optimized geometry and the calculated frequencies are in good agreement with the experimental data.