Preservation of the 2H-MoS₂ structure in intercalation compounds with bulky cations

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Friedrich, Daniel ; Flöter, Eberhard Lukas ; Pauly, Fabian:
Preservation of the 2H-MoS₂ structure in intercalation compounds with bulky cations.
In: Dalton Transactions. Bd. 55 (2026) Heft 29 . - S. 10951-10958.
ISSN 1477-9234
DOI: https://doi.org/10.1039/d6dt01035k

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Abstract

Layered molybdenum disulfide (MoS2) is a model transition metal dichalcogenide (TMD) whose properties can be tuned via redox-driven intercalation and phase control. In this work, we present a one-pot wet-chemical synthesis route to form MoS2 intercalation compounds using pyrenide salts with cationic potassium crown-ether complexes, K(15-crown-5)2C16H10 and K(18-crown-6)C16H10. These salts act as combined reducing and intercalating agents. Under optimised conditions in dimethyl sulfoxide at 150 °C, pyrenide affords well-ordered crystalline products, whereas more strongly reducing polycyclic aromatic hydrocarbanions yield only partially ordered phases, highlighting the role of redox potential and kinetics. X-ray powder diffraction shows an expansion of the basal spacing from 6.13 Å in pristine 2H-MoS2 to 15.05 Å and 16.05 Å, consistent with complexed [K(15-crown-5)2]+ and [K(18-crown-6)]+ cations occupying the interlayer galleries, respectively. Raman spectroscopy and atomic absorption spectroscopy confirm preservation of the 2H phase at a low to moderate reduction level (∼8–12%). Calculations using density functional theory (DFT) and a jellium model show that at such charge densities and large interlayer distances, 2H-MoS2 remains energetically favored over the 1T/1T′ phase, rationalizing the coexistence of large gallery expansion with a semiconducting host lattice.