Crystal structure, vibrational and optical properties of N-(3-ammoniumpropyl)-1,3 diammoniumpropane hexabromobismuthate monohydrate: [C6H20N3]BiBr6 H2O

Dimensional Reduction of Cs2 AgBiBr6 : A 2D Hybrid Double Perovskite with Strong Polarization Sensitivity

By dimensional reduction of the 3D motif of Cs₂ AgBiBr₆ , a lead-free 2D hybrid double perovskite, (i-PA)₂ CsAgBiBr₇ (1, i-PA=isopentylammonium), was successfully designed. It adopts a quantum-confined bilayered structure with alternating organic and inorganic sheets. Strikingly, the unique 2D architecture endows it highly anisotropic nature of physical properties, including electric conductivity and optical absorption (the ratio α_b /α_c =1.9 at 405 nm). Such anisotropy attributes result in the strong polarization-sensitive responses with large dichroic ratios up to 1.35, being comparable to some 2D inorganic materials. This is the first study on the hybrid double perovskites with strong polarization sensitivity. A crystal device of 1 also exhibits rapid response speed (ca. 200 μs) and excellent stabilities. The family of 2D hybrid double perovskites are promising optoelectronic candidates, and this work paves a new pathway for exploring new green polarization-sensitive materials.

DFT computations on: Crystal structure, vibrational studies and optical investigations of a luminescent self-assembled material

The current work undertakes the growth and the physicochemical properties of a novel green-yellow luminescence semi-organic material, the 3-picolylammonium bromide abbreviated (Pico-Br). In this paper, we report the X-ray diffraction measurements which show that the crystal lattice consists of distinct 3-picolylammonium cations and free bromide anions connected via NH⋯Br and NH⋯N hydrogen bonds leading to form a two dimensional frameworks. Molecular geometry compared with its optimized counterpart shows that the quantum chemical calculations carried out with density functional method (DFT) well produce the perceived structure by X-ray resolution of the studied material. To provide further insight into the spectroscopic properties, additional characterization of this material have been performed with Raman and infrared studies at room temperature. Theoretical computations have been computed using the (DFT) method at B3LYP/LanL2DZ level of theory implemented within Gaussian 03 program to study the vibrational spectra of the investigated molecule in the ground state. Optical absorption spectrum inspected by UV-visible absorption reveals the appearance of sharp optical gap of 280nm (4.42eV) as well as a strong green photoluminescence emission at 550nm (2.25eV) is detected on the photoluminescence (PL) spectrum at room temperature. Using the TD/DFT method, HOMO-LUMO energy gap and the Mulliken atomic charges were calculated in order to get an insight into the material. Good agreement between the theoretical results and the experimental ones was predicted.

Synthesis, crystal structure and Hirshfeld surface analysis of a polymeric bismuthate(III) halide complex, (C6H6N3)2[BiCl5]·2H2O

The structure of this new halide-bridged polymer comprises polyanionic zigzag chains of formula [(BiCl₅)²⁻]_n running along the c-axis direction. The 1,2,3-benzotriazolium cations are linked between these polymer chains, via the water mol­ecules, giving rise to left- and right-handed helical chains.

The synthesis and the crystal structure of a new halide-bridged polymer, namely catena-poly[bis­(1,2,3-benzotriazolium) [[tetra­chlorido­bis­muth(III)]-μ-chlorido] dihydrate], {(C₆H₆N₃)₂[BiCl₅]·2H₂O}_n are reported. The structure comprises polyanionic zigzag chains of formula [(BiCl₅)²⁻]_n running along the c-axis direction. The 1,2,3-benzotriazolium cations are linked between these polymer chains, via the water mol­ecules, giving rise to left- and right-handed helical chains. Hirshfeld surface analysis and fingerprint plots were used to decode the inter­molecular inter­actions in the crystal network and determine the contribution of the component units for the construction of the three-dimensional architecture.

Crystal structure, vibrational spectra, optical and DFT studies of bis (3-azaniumylpropyl) azanium pentachloroantimonate (III) chloride monohydrate (C6H20N3)SbCl5·Cl·H2O

The crystal structure of (C₆H₂₀N₃)SbCl₅·Cl·H₂O is built up of [NH₃(CH₂)₃NH₂(CH₂)₃NH₃]³⁺ cations, [SbCl₅]^2- anions, free Cl^- anions and neutral water molecules connected together by NH⋯Cl, NH⋯O and OH⋯Cl hydrogen bonds. The optical band gap determined by diffuse reflection spectroscopy (DRS) is 3.78eV for a direct allowed transition. Optimized molecular geometry, atomic Mulliken charges, harmonic vibrational frequencies, HOMO-LUMO and related molecular properties of the (C₆H₂₀N₃)SbCl₅·Cl·H₂O compound were calculated by Density functional theory (DFT) using B3LYP method with GenECP sets. The calculated structural parameters (bond lengths and angles) are in good agreement with the experimental XRD data. The vibrational unscaled wavenumbers were calculated and scaled by a proper scaling factor of 0.984. Acceptable consistency was observed between calculated and experimental results. The assignments of wavenumbers were made on the basis of potential energy distribution (PED) using Vibrational Energy Distribution Analysis (VEDA) software. The HOMO-LUMO study was extended to calculate various molecular parameters like ionization potential, electron affinity, global hardness, electro-chemical potential, electronegativity and global electrophilicity of the given molecule.