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 P1̅ with the unit cell parameters a = 7.761(1) Å, b = 9.259(1) Å, c = 9.689(1) Å, α = 95.68(3)°, β = 103.19(3)°, γ = 93.56(3)°, and Z = 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.