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Multinary Chalcogenido Metalates

Colored Zeolite Analogs

In protic solvents, ortho-chalcogenido tetrelate anions [TE4]4– (T: Ge, Sn; E: S, Se, Te) react with transition metal ions Mn+ to form heterobimetallic anionic substructures [MxTyEz]q–. The anions represent coordination polymers adopting a diversity of strands, layers or 3D-networks, which are related to zeolite structures. Other products represent molecular clusters, which most often accord with Tn-type or Pn-type supertetrahedral motifs (Figure 1).

Scheme for the linkage of small tin selenium supertetrahedron fragments via transition metal cation
Foto: Stefanie Dehnen

Figure 1: Formal connection of the porous threedimensional HgSnSe network and the molecular anion [Hg4Sn4Se17]10–.

Here, you see a cutout from the crystal structure of Li10SnP2S12 along the cristallografical a-axis.
Photo: Stefanie Dehnen

With atoms from periods 3-6 in combination with transition metal atoms, the resulting multinary chalcogenido metalate salts usually exhibit narrow band gaps. They thus behave like "colored zeolite analogs", which combine structural features of zeolites with adjustable opto-electronic properties of semiconductors. Additionally, some of the networks exhibit electronic or ion conductivity, which makes them interesting for use as solid electrolytes. Other synthetic approaches to such multinary chalcogenid metalates are carried out in ionic liquids, in chalcogenide flux, or at high temperatures. This way, we succeeded in the synthesis of Li or sodium superion conductors based on chalcogenido tetrelate anions (Figure 2).

Figure 2: crystal structure of the lithium ion superconductor Li10SnP2S12.

see e.g.: a) M. Duchardt, S. Neuberger, U. Ruschewitz, T. Krauskopf, W. Zeier, J. Schmedt auf der Günne, S. Adams, B. Roling, S. Dehnen, Chem. Mater. 2018, 30, 4134–4139. DOI; b) M. Duchardt, U. Ruschewitz, S. Adams, S. Dehnen, B. Roling, Angew. Chem. 2018, 129, 1365–1369. DOI; Angew. Chem. Int. Ed. 2018, 57, 1351–1355. DOI; c) T. Kaib, P. Bron, S. Haddadpour, L. Mayrhofer, L. Pastewka, T.T. Järvi, M. Moseler, B. Roling, S. Dehnen, Chem. Mater. 2013, 25, 2961–2969. DOI; b) P. Bron, S. Johansson, K. Zick, J. Schmedt auf der Günne, S. Dehnen, B. Roling, J. Am. Chem. Soc. 2013, 135, 15694–15697. DOI; Highlights: idw - Informationsdienst Wissenschaft, 13.11.2013; eMobilitätOnline.de - Portal für Angewandte Elektromobilität, 14.11.2013; C&EN, 14.11.2016, 94, 30–32. Weblink

Experimental and theoretical investigations of physical and magnetic properties of metalla-chalcogenido tetrelates

Compounds that comprise anions [MxTyEz]q– show optical absorption in the visible range of the spectrum. Their excitation energy Eg may be fine-tuned by the appropriate choice of M and E. Owing to the exceptional heterobimetallic nature of the anions, the optical gaps are significnatly smaller than for structurally related binary compounds, reaching down to metallic luster of the crystals. Furthermore, the choice of M is decisive for the occurrence of magnetism and magnetic coupling. Optical and magnetic properties are investigated and explained through corresponding experiments as well as by in-depth quantum chemical calculations (Figures 3 and 4).

Here, you see some UV-VIS spectra of ternary compounds, differing in the transition metal element.
Photo: Stefanie Dehnen

Figure 3: Fine-tuning of the band gaps, illustrated by UV/Vis spectra of the salts [K10(HOR)m][M4Sn4E17].

Here, you see a picture of magnetical couplings in a ternary anion.
Photo: Stefanie Dehnen
Here, youe see a Chi against T Plot
Photo: Stefanie Dehnen

Figure 4: Magnetic coupling in [Mn4Sn4E17]10, calculated by means of density functional theory (DFT) methods (top) and observed experimentally (chi versus T plot) in [K10(H2O)16(MeOH)0.5][Mn 4Sn4Se17] (bottom).

see e.g.: a) P. Bron, B. Roling, S. Dehnen, J. Power Sources 2017, 352, 127–134. DOI; b) F. Lips, S. Dehnen, Inorg. Chem. 2008, 47, 5561–5563. DOI; c) E. Ruzin, A. Fuchs, S. Dehnen, Chem. Commun. 2006, 4796-4798. DOI