Structural, optical, and magnetic properties of Na8Eu2(Si2S6)2 and Na8Eu2(Ge2S6)2: Europium(II) quaternary chalcogenides that contain an ethane-like (Si2S6)6- or (Ge2S6)6- moiety

Amitava Choudhury
Kartik C. Ghosh, Missouri State University
Fernande Grandjean
Gary J. Long
Peter K. Dorhout

Abstract

Two isostructural europium(II) quaternary chalcogenides, Na Eu (Si S ) , 1, and Na Eu (Ge S ) , 2, containing an ethane-like (Si S ) or (Ge S ) moiety have been synthesized by employing the polychalcogenide molten flux method. Single-crystal X-ray diffraction reveals that both compounds crystallize in the C2/m space group, and their structures contain layers of {[Na Eu (Si S ) ] } or {[Na Eu (Ge S ) ] } anions held together by six interlayer sodium cations to yield {Na [Na Eu (Si S ) ]} and {Na [Na Eu (Ge S ) ]} . Compound 2 is a semiconductor with an optical band gap of 2.15(2) eV. The temperature dependence of the magnetic susceptibility indicates that compounds 1 and 2 are paramagnetic with μ =7.794(1) μ per Eu and g=1.964(1) for 1 and μ =8.016(1) μ per Eu and g=2.020(1) for 2, moments that are in good agreement with the europium(II) spin-only moment of 7.94 μ . The europium-151 Mössbauer isomer shift of 2 confirms the presence of europium(II) cations with an electronic configuration between [Xe]4f and 4f 6s . 8 2 2 6 2 8 2 2 6 2 2 6 2 6 2 2 2 6 2 ∞ 2 2 2 6 2 ∞ 6 2 2 2 6 2 ∞ 6 2 2 2 6 2 ∞ eff B eff B B 6- 6- 6- 6- 6.81 7 0.32