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. - Highlights: • A new luminescent organic-inorganic material (C₆H₁₄N)₂BiBr₅ was synthesized. • Vibrational properties were studied by Raman and IR spectroscopy. • The UV–vis spectrum shows three absorption peaks at 3.01, 3.73 and at 4.4 eV. • This compound shows a strong blue emission at 2.71 eV