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      https://www.ias.ac.in/article/fulltext/jcsc/129/02/0167-0175

    • Keywords

       

      Selenidogermanates; nickel; solvothermal syntheses; crystal structures; optical properties

    • Abstract

       

      New selenidogermanate salts [NH₄] ₂ [H₂N(CH₃) ₂] ₂Ge₂Se₆ (1) and [Ni(dien) ₂] ₂Ge₂Se5(Se₂) (2) (dien = diethylenetriamine), and a selenidogermanate complex [{Ni(tepa)} ₂ (μ-Ge₂Se₆)] (3) (tepa = tetraethylenepentamine) were prepared by solvothermal reactions. Compounds 1 and 2 consist of discrete [Ge₂Se₆] ⁴⁻ and [Ge₂Se₇] ⁴⁻ anions, and NH⁺₄, [H₂N(CH₃) ₂] ⁺ and [Ni(dien) ₂] ²⁺ counter cations, respectively. The [Ge₂Se₆] ⁴⁻ anion is constructed by two tetrahedral GeSe₄ building units via edge-sharing. In 2, two tetrahedral GeSe₄ units are linked by a corner and a Se–Se bond to form a polyselenidogermanate anion [Ge₂Se₇] ⁴⁻containing a five-membered ring Ge2Se3. The dimeric [Ge₂Se₆] ⁴⁻ anion acts as a bridging ligand via the trans terminal Se atoms to link two [Ni(tepa)] ²⁺ cations, resulting in neutral complex 3. The Ni²⁺ ion in 2 is coordinated by two tridentate dien ligands, while it is coordinated by a pentadentate tepa ligand and a selenidogermanateanion in 3. The different coordination environments of Ni²⁺ ions indicate the influence of the denticity of ethylene polyamines on the formation of selenidogermanates in the presence of transition metal ions. Thecompounds 1–3 exhibit optical band gaps between 2.06 and 2.35 eV.

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