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.
Despite remarkable progress in photoconversion efficiency, the toxicity of lead-based hybrid perovskites remains an important issue hindering their applications in consumer optoelectronic devices, such as solar cells, LED displays, and photodetectors. For that reason, lead-free metal halide complexes have attracted great attention as alternative optoelectronic materials. In this work, we demonstrate that reactions of two aromatic diamines with iodine in hydroiodic acid produced phenylenediammonium (PDA) and N,N-dimethyl-phenylenediammonium (DMPDA) triiodides, PDA(I3)2·2H2O and DMPDA(I3)I, respectively. If the source of bismuth was added, they were converted into previously reported PDA(BiI4)2·I2 and new (DMPDA)2(BiI6)(I3)·2H2O, having band gaps of 1.45 and 1.7 eV, respectively, which are in the optimal range for efficient solar light absorbers. All four compounds presented organic–inorganic hybrids, whose supramolecular structures were based on a variety of intermolecular forces, including (N)H⋯I and (N)H⋯O hydrogen bonds as well as I⋯I secondary and weak interactions. Details of their molecular and supramolecular structures are discussed based on single-crystal X-ray diffraction data, thermal analysis, and Raman and optical spectroscopy.
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