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).I-2] (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 I-2. It crystallizes in triclinic space group P1 with the unit cell parameters a = 7.761(1) angstrom, b = 9.259(1) angstrom, c = 9.689(1) angstrom, alpha = 95.68(3)degrees, beta = 103.19(3)degrees, gamma = 93.56(3)degrees, 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](infinity)-one-dimensional anionic chains; the second level features secondary bonds between the chains and I-2 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).I-2] is a semiconductor with the band gap of 1.45 eV.