Hybrid organic-inorganic bismuth(III)-based material [4-NH2C5H4NH]7[BiCl6]2Cl. Crystal structure, dielectric properties and molecular motions of 4-aminopyridinium cations

Crystal engineering and structural diversity of 2-aminopyridinium hypodiphosphates obtained by crystallization and dehydration

Organic-inorganic salts and ionic co-crystals of hypodiphosphoric acid (H4P2O6) with 2-aminopyridne (2ap) have been synthesized and characterized by X-ray crystallography, thermogravimetry, element analysis and Fourier-transform infared spectroscopy. (2apH)4(H3P2O6)2(H2P2O6)∙2H2O (1), (2apH)2(H2P2O6)∙2H2O...

Halobismuth(III) salts with substituted aminopyridinium cations

The crystal structures of six halobismuth(III) salts of variously substituted aminopyridinium cations display discrete mononuclear [BiCl₆]^3- and dinuclear [Bi₂X₁₀]^4- anions (X = Cl or Br), and polymeric cis-double-halo-bridged [Bi_nX_4n]^n- anionic chains (X = Br or I). Bis(2-amino-3-ammoniopyridinium) hexachloridobismuth(III) chloride monohydrate, (C₅H₉N₃)₂[BiCl₆]Cl·H₂O, (1), contains discrete mononuclear [BiCl₆]^3- and chloride anions. Tetrakis(2-amino-3-methylpyridinium) di-μ-chlorido-bis[tetrachloridobismuth(III)], (C₆H₉N₂)₄[Bi₂Cl₁₀], (2), tetrakis(2-amino-3-methylpyridinium) di-μ-bromido-bis[tetrabromidobismuth(III)], (C₆H₉N₂)₄[Bi₂Br₁₀], (3), and bis(4-amino-3-ammoniopyridinium) di-μ-chlorido-bis[tetrachloridobismuth(III)] dihydrate, (C₅H₉N₃)₂[Bi₂Cl₁₀]·2H₂O, (4), incorporate discrete [Bi₂X₁₀]^4- anions (X = Cl or Br), while catena-poly[2,6-diaminopyridinium [[cis-diiodidobismuth(III)]-di-μ-iodido]], {(C₅H₈N₃)[BiI₄]}_n, (5), and catena-poly[2,6-diaminopyridinium [[cis-dibromidobismuth(III)]-di-μ-bromido]], {(C₅H₇N₂)[BiBr₄]}_n, (6), include [Bi_nX_4n]^n- anionic chains (X = Br or I). Structures (2) and (3) are isostructural, while that of (5) is a pseudomerohedral twin. There is no discernible correlation between the type of anionic species obtained and the cation or halide ligand used. The Bi^III centres always have a slightly distorted octahedral geometry and there is a correlation between the Bi-X bond lengths and the number of classic N-H...X hydrogen bonds that the X ligand accepts, with a greater number of interactions corresponding with slightly longer Bi-X distances. The supramolecular networks formed by classic N-H...X hydrogen bonds include ladders, bilayers and three-dimensional frameworks.

Phase transitions in (C7 H12 N2 )2 [SnCl6 ]Cl2 ·1.5H2 O crystal, studied by NMR and infrared spectroscopy

The (C₇ H₁₂ N₂ )₂ [SnCl₆ ]Cl₂ ·1.5H₂ O complex is a new member of the family of hybrid organic-inorganic perovskite compounds. It exhibits two order-disorder phase transitions with changes in the conformation of aromatic cations at the two transition temperatures 360 and 412 K. Differential scanning calorimetry, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FT-IR) spectroscopy were used to investigate these phase transitions. These transition mechanisms were investigated in terms of the spin-lattice relaxation times T1 for ¹ H static NMR and the chemical shifts for ¹³ C CP-MAS. The temperature dependence of T1(¹ H) and ¹³ C chemical shifts are changed near T_C1 and T_C2 . Furthermore, the splitting for ¹³ C NMR signals in Phases (II) and (III) indicated a ferroelastic characteristic of the compound. In addition, FT-IR results indicate that the ordered conformational structure of aromatic cations undergoes a remarkable disorder with increasing temperature. The NMR and FT-IR studies suggest that the phase transition mechanisms are related to the reorientational motion of [C₇ H₁₂ N₂ ]²⁺ cations as a whole. Phase transition was examined in light of the interesting optical properties of this material.