Tetrathiafulvalene-based double metal lead iodides: structures and electrical properties

Area of Science:

• Materials Science
• Solid-State Chemistry
• Organic-Inorganic Hybrid Materials

Background:

• Incorporating electronically active organic components into metal halides enhances their electronic properties.
• Previous work synthesized hybrid halides with tetrathiafulvalenes (TTFs) and lead/bismuth halides, showing improved electronic characteristics.
• This research expands the investigation to double metal halides featuring mixed lead and copper transition metals.

Purpose of the Study:

• To synthesize and characterize novel hybrid TTF-based double metal halides.
• To investigate the structural diversity and electronic properties of these new compounds.
• To compare the electronic and optoelectronic performance of mixed metal halides with monometal analogues.

Main Methods:

• Crystallographic characterization of four new hybrid compounds: [TTF]5[Pb2Cu2I10]·H2O (1), [TTF]2[PbCu2I6] (2), [TTF]2[Cu4I6]·H2O (3), and [TTF]2[Ag4I6] (4).
• Analysis of anion structures (0D cluster in 1, 1D chains in 2-4) and TTF moiety stacking (2D framework in 1, 1D columns in 2-4).
• Evaluation of semiconductor properties, conductivity, and photoconductivity.

Main Results:

• Two novel hybrid TTF-lead-cuprous iodides and two monometal analogues were synthesized and structurally characterized.
• The study identified novel 0D cluster and 1D chain anion structures for the first time.
• Mixed metal iodides demonstrated superior conductivity and photoconductivity compared to monometal iodides.
• Semiconductor properties were found to correlate with electron donation from anion to cation and the electronic state of TTF cations.

Conclusions:

• The incorporation of TTF into mixed lead-copper iodide frameworks leads to novel structures with enhanced electronic properties.
• Mixed metal halide compounds exhibit superior conductivity and photoconductivity over monometal analogues, highlighting the benefit of compositional complexity.
• The electronic state of TTF cations and charge transfer dynamics are critical factors influencing the optoelectronic performance of these hybrid materials.