Reduction of Germanium Oxides-The Mixed-Valence Germanates A2Ge4O7 (A = Na, K).
Inorg Chem
; 63(11): 5227-5234, 2024 Mar 18.
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| MEDLINE
| ID: mdl-38451057
ABSTRACT
We report on the synthesis of two-layered alkali germanates, Na2Ge4O7 and K2Ge4O7. Both compounds were synthesized by using the ammonothermal method at 823 K and 100 MPa. Under these conditions, germanium is partially reduced from the +IV state to +II, forming mixed-valence compounds with the rarely observed [Ge(II)O3]4- unit. The valence state was verified by X-ray photoelectron spectroscopy (XPS) and was accompanied by theoretical calculations alongside vibrational spectroscopy and single-crystal X-ray structure determination. The compounds crystallize in the trigonal space groups (Na2Ge4O7 P3Ì
c1 and K2Ge4O7 P3Ì
m1) and feature layers of corner sharing [Ge(II)O3]4- and [Ge(IV)2O7]6- units forming [Ge(II)2Ge(IV)2O7]2- polyanions. These layers are separated by alkali metal ions. The compounds are colorless insulators with band gaps of 4.0-4.2 eV. According to the Robin-Day classification, both compounds can be described as class I materials, where the valences are trapped on specific sites.
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MEDLINE
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En
Revista:
Inorg Chem
Año:
2024
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Article
País de afiliación:
Alemania