AuPb₂I₇: A Narrow Bandgap Au³⁺ Iodide Semiconductor

Area of Science:

• Inorganic Chemistry
• Materials Science
• Solid-State Chemistry

Background:

• Ternary metal halides are a class of compounds with diverse structural and electronic properties.
• Gold(III) halides are less explored compared to other transition metal halides, offering opportunities for novel material discovery.
• Understanding structure-property relationships in new materials is crucial for developing advanced applications.

Purpose of the Study:

• To synthesize and characterize a novel ternary halide containing gold(III).
• To elucidate the crystal structure and electronic properties of the new compound, AuPb₂I₇.
• To investigate the stability and potential applications of this material.

Main Methods:

• Synthesis of AuPb₂I₇ via reactions involving gold(I) iodide (AuI), lead(II) iodide (PbI₂), and iodine (I₂).
• Single-crystal X-ray diffraction for crystallographic analysis (triclinic P1̅ space group).
• Density functional theory (DFT) calculations to determine electronic band structure and bandgap.

Main Results:

• Isolation and structural determination of the novel ternary halide AuPb₂I₇.
• The compound features a unique three-dimensional structure with [Pb₂I₇]^3- pseudolayers bridged by square planar Au³⁺ ions.
• AuPb₂I₇ exhibits an indirect bandgap of 1.17 eV, primarily arising from Au-I metal-ligand charge transfer, and shows moderate air stability.

Conclusions:

• The successful synthesis and characterization of AuPb₂I₇ expand the family of ternary gold halides.
• The unique crystal structure and indirect semiconductor bandgap suggest potential for optoelectronic applications.
• Further research is warranted to explore its properties and potential degradation mechanisms.