Self-assembling iron and manganese metal–germanium–selenide frameworks: [NMe4]2MGe4Se10, where M = Fe or Mn

Abstract

The hydrothermal synthesis mixture Ge–Se–(TMA)OH–H₂O (TMA⁺ = NMe₄⁺) yielded crystals of the material (TMA)₄Ge₄Se₁₀. A single-crystal X-ray diffraction structure showed the presence of adamantanoid Ge₄Se₁₀^4– clusters and TMA⁺ cations. The TMA⁺ template-mediated aqueous synthesis of (TMA)₂MGe₄Se₁₀ (M = Mn or Fe) from Ge₄Se₁₀^4– and M²⁺ building-blocks is described. Rietveld powder X-ray diffraction full profile structure refinements of (TMA)₂MGe₄Se₁₀ established that these novel metal–germanium–selenide frameworks are isostructural with the analogous metal–germanium–sulfides, (TMA)₂MGe₄S₁₀. The selenide materials have a zinc blende-type of open-framework structure. Charge-balance of the anionic open-framework [MGe₄Se₁₀]^2– is maintained by two TMA⁺ template cations that reside within the cavity spaces. Trends in the tetragonal unit cell dimensions and metal–chalcogenide bond lengths of (TMA)₂MGe₄X₁₀ (X = S or Se) are those expected based upon increases in metal and chalcogenide radii on passing from S^–II to Se^–II and Fe^II to Mn^II.