Different Chemical Environments of [Ge₄Se₁₀]^4– in the Li⁺ Compounds [Li₄(H₂O)₁₆][Ge₄Se₁₀]·4.33H₂O, [{Li₄(thf)₁₂}Ge₄Se₁₀], and [Li₂(H₂O)₈][MnGe₄Se₁₀], and Ionic Conductivity of Underlying “Li₄Ge₄Se₁₀”

Abstract

The crystalline selenido germanates [Li₄(H₂O)₁₆][Ge₄Se₁₀]·4.3H₂O (1), [{Li₄(thf)₁₂}Ge₄Se₁₀] (2), and [Li₂(H₂O)₈][MnGe₄Se₁₀] (3) (thf = THF = tetrahydrofuran) were obtained by an extraction of a glassy ternary phase of the nominal composition Li₄Ge₄Se₁₀ (=Li₂S·2GeSe₂) with water (1) or THF (2) and slow evaporation of the solvent or by being layered with MnBr₂ in H₂O/MeOH (3), respectively. The compounds contain known selenido germanate anions, however, for the first time with Li⁺ counterions. This is especially remarkable for the prominent _∞³{[MnGe₄Se₁₀]^2-} open-framework structure, which was reported to crystallize with (NMe₄)⁺, Cs⁺, Rb⁺, and K⁺ counterions, but it has not yet been realized with the smallest alkali metal cation. Impedance spectroscopic studies on Li₄Ge₄Se₁₀ classify the glassy solid as a moderate Li⁺ ion conductor.