Role of I₂ Molecules and Weak Interactions in Supramolecular Assembling of Pseudo-Three-Dimensional Hybrid Bismuth Polyiodides: Synthesis, Structure, and Optical Properties of Phenylenediammonium Polyiodobismuthate(III)

Phenylenediammonium polyiodobismuthate­(III), [PDA­(BiI₄)₂·​I₂] (PDA = phenyl­ene­diam­monium, [NH₃­C₆H₄­NH₃]²⁺), represents a new hybrid halometallate synthesized in a form of black well-shaped crystals by a facile reaction in aqueous solution of HI containing dissolved I₂. It crystallizes in triclinic space group <i>P</i>1̅ with the unit cell parameters <i>a</i> = 7.761(1) Å, <i>b</i> = 9.259(1) Å, <i>c</i> = 9.689(1) Å, α = 95.68(3)°, β = 103.19(3)°, γ = 93.56(3)°, and <i>Z</i> = 1. Its crystal structure comprises three levels of organization discriminated by a type of chemical bonding. The first level is provided by covalently bonded [BiI₆] octahedra linked into [BiI₄]_∞^– one-dimensional anionic chains; the second level features secondary bonds between the chains and I₂ bridging molecules, whereas the third level is specified by the weak hydrogen N–H···I bonds involving a diammonium cation and I···I intermolecular interactions that additionally link anionic chains. Altogether, these three interaction types ensure the formation of a complex pseudo-three-dimensional crystal structure. According to optical absorption study, [PDA­(BiI₄)₂·​I₂] is a semiconductor with the band gap of 1.45 eV

Iodobismuthates Containing One-Dimensional BiI₄^– Anions as Prospective Light-Harvesting Materials: Synthesis, Crystal and Electronic Structure, and Optical Properties

Four iodobismuthates, LiBiI₄·5H₂O (<b>1</b>), MgBi₂I₈·8H₂O (<b>2</b>), MnBi₂I₈·8H₂O (<b>3</b>), and KBiI₄·H₂O (<b>4</b>), were prepared by a facile solution route and revealed thermal stability in air up to 120 °C. Crystal structures of compounds <b>1</b>–<b>4</b> were solved by a single crystal X-ray diffraction method. <b>1</b>: space group <i>C</i>2/<i>c</i>, <i>a</i> = 12.535(2), <i>b</i> = 16.0294(18), <i>c</i> = 7.6214(9) Å, β = 107.189(11)°, <i>Z</i> = 4, <i>R</i> = 0.029. <b>2</b>: space group <i>P</i>2₁/<i>c</i>, <i>a</i> = 7.559(2), <i>b</i> = 13.1225(15), <i>c</i> = 13.927(4) Å, β = 97.14(3)°, <i>Z</i> = 2, <i>R</i> = 0.031. <b>3</b>: space group <i>P</i>2₁/<i>c</i>, <i>a</i> = 7.606(3), <i>b</i> = 13.137(3), <i>c</i> = 14.026(5) Å, β = 97.14(3)°, <i>Z</i> = 2, <i>R</i> = 0.056. <b>4</b>: space group <i>P</i>2₁/<i>n</i>, <i>a</i> = 7.9050(16), <i>b</i> = 7.7718(16), <i>c</i> = 18.233(4) Å, β = 97.45(3)°, <i>Z</i> = 4, <i>R</i> = 0.043. All solid state structures feature one-dimensional (BiI₄)⁻ anionic chains built of [BiI₆] octahedra that share two opposite edges in such a fashion that two iodine atoms in <i>cis</i>-positions remain terminal. The calculated electronic structures and observed optical properties confirmed that compounds <b>1</b>–<b>4</b> are semiconductors with direct band gaps of 1.70–1.76 eV, which correspond to their intense red color. It was shown that the cations do not affect the optical properties, and the optical absorption is primarily associated with the charge transfer from the I 5p orbitals at the top of the valence band to the Bi 6p orbitals at the bottom of the conduction band. Based on their properties and facile synthesis, the title compounds are proposed as promising light-harvesting materials for all-solid solar cells