Hydrogen Bonding Controls the Structural Evolution in Perovskite-Related Hybrid Platinum(IV) Iodides

Area of Science:

• Solid-state chemistry
• Materials science
• Inorganic chemistry

Background:

• Hybrid hexaiodoplatinate(IV) compounds (A₂PtI₆) are structurally analogous to lead-based hybrid halide perovskites.
• These materials are of interest due to their potential applications in optoelectronics, mirroring the success of perovskites.
• Understanding structure-property relationships is crucial for designing new functional materials.

Purpose of the Study:

• To investigate the solid-state structural evolution in four hybrid hexaiodoplatinate(IV) compounds.
• To elucidate the role of hydrogen bonding in directing the crystal structures of these materials.
• To explore the electronic properties and structural trends in relation to cation size and bonding.

Main Methods:

• Synthesis and characterization of four A₂PtI₆ compounds (A = NH₄⁺, CH₃NH₃⁺, CH(NH₂)₂⁺, C(NH₂)₃⁺).
• Solid-state ¹⁹⁵Pt and ¹H NMR spectroscopy to probe local environments and bonding.
• Density functional theory (DFT) calculations to analyze structural trends, hydrogen bonding, and electronic band structures.

Main Results:

• Three compounds (NH₄⁺, CH₃NH₃⁺, CH(NH₂)₂⁺) adopt the vacancy-ordered double perovskite structure (A₂Pt□I₆).
• Guanidinium compound (GUA)₂PtI₆ crystallizes in a K₂MnF₆ structure, a variant of the hexagonal CsNiCl₃ type.
• Extended hydrogen bonding significantly influences the structural arrangements across the series.
• DFT calculations and optical properties reveal surprisingly dispersed conduction bands in smaller A-cation compounds, despite a lack of direct I-Pt-I connectivity.

Conclusions:

• Hydrogen bonding is a key factor in determining the solid-state structures of hybrid hexaiodoplatinate(IV) compounds.
• These iodosalt compounds exhibit structural diversity and electronic properties comparable to hybrid halide perovskites.
• The observed electronic behavior challenges conventional understanding, highlighting the potential for novel optoelectronic applications.