Low-Temperature Synthesis and Characterization of Hybrid Heavy Metal Zero- Dimensional Cluster Compounds Containing Pt/Ir and Bi

TL;DR

Scientists created new cluster compounds using platinum, iridium, and bismuth at low temperatures, which could be useful for semiconducting applications.

Contribution

The synthesis of three novel zero-dimensional cluster compounds containing Pt/Ir and Bi at low temperatures in an ionic liquid.

Findings

Three distinct cluster-containing salts were synthesized and crystallized in different structure types.

Molecular DFT calculations revealed HOMO–LUMO gaps of 3.3774 eV, 3.2332 eV, and 2.4106 eV for the anionic clusters.

The compounds feature unique combinations of light and heavy elements balanced by [BMIm]+ ions.

Abstract

Three novel hybrid organic-inorganic cluster compounds comprising 5d heavy metals (M = Pt, Ir) and Bi were synthesized at 180 °C in ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), which served both as reactant and reaction medium. Stoichiometric reactions between the appropriate metal halide and [BMIm][BF4] yielded three distinct cluster-containing salts: [PtBi6Cl12][BMIm]2, [Pt2Bi12Br22][BMIm]2, and [IrBi6Cl12][BMIm]3, all crystallizing in three different structure types. [PtBi6Cl12][BMIm]2 crystallizes in the monoclinic space group P21/c with the unit cell parameters of a = 9.1154(5), b = 9.0692(4), c = 23.8159(13), and β = 93.890(2) while [IrBi6Cl12][BMIm]3 crystallizes in the monoclinic space group C2/c (a = 22.0181(7), b = 12.6726(4), c = 35.2412(11), β = 95.132(1)) both featuring cuboctahedral [MBi6Cl12]x– (x = 2, 3) anionic clusters. The Br-bearing analog [Pt2Bi12Br22][BMIm]2 crystallizes in the triclinic space group P (a = 9.3063(3), b = 12.4615(4), c = 14.7424(5), α =70.484 (10), β = 87.966(10), γ = 87.497(10)) and exhibits double cuboctahedra [PtBi12Br22]2– cluster. Each cluster anion is charge-balanced by [BMIm]+ ions, providing a unique combination of the lightest and heaviest elements in the title compounds. Molecular DFT calculations reveal that each anionic cluster, [PtBi6Cl12]2–, [IrBi6Cl12]3–, [PtBi12Br22]2– has HOMO–LUMO gaps of 3.3774 eV, 3.2332 eV and 2.4106 eV respectively. Details of the synthesis, crystal and electronic structures, and perspectives for semiconducting applications are discussed.