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

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.