Semiconducting Quasi One-Dimensional (PbBr₂)[Pb₂P₁₄]₂, a Lead Bromide Adduct and Violet Phosphorus Derivative

Materials with low dimensionality have been identified as potential candidates for electronic and optoelectronic applications. Semiconducting polyphosphides with one-dimensional (1D) substructures, such as materials adopting the HgPbP₁₄-structure type or Pb₅I₂P₂₈, are examples of this class. Herein, we report on (PbBr₂)[Pb₂P₁₄]₂ that crystallizes monoclinically, in space group P2₁/n (No. 14), with the cell parameters a = 9.8175(7) Å, b = 17.5841(11) Å, c = 18.9568(15) Å, and β = 97.612(6)°. The title compound consists of formal charge-neutral PbBr₂ units that interlink (Formula presented.) entities, resulting in a more descriptive formula (PbBr₂)[Pb₂P₁₄]₂ rather than the sum formula Pb₅Br₂P₂₈. Raman spectroscopy was used to support this adduct description, indicating that the title compound exhibits a bonding situation within the Pb substructure similar to PbBr₂. First-principle density functional theory (DFT) calculations on (PbBr₂)[Pb₂P₁₄]₂ and isostructural (PbI₂)[Pb₂P₁₄]₂ (Pb₅I₂P₂₈) illustrate typical semiconductor behavior for these two polyphosphides. Photoluminescence spectroscopy shows two band gaps at 1.90 and 1.79 eV in both (PbBr₂)[Pb₂P₁₄]₂ and (PbI₂)[Pb₂P₁₄]₂, which align with the calculated values found from DFT calculations.