Quiroga-González, Enrique, Näther, Christian and Bensch, Wolfgang (2010) The thioantimonate anion [Sb4S8]4− acting as a tetradentate ligand: Solvothermal synthesis, crystal structure and properties of {[In(C6H14N2)2]2Sb4S8}Cl2 exhibiting unusual uniaxial negative and biaxial positive thermal expansion. Solid State Sciences, 12 (7). pp. 1235-1241. DOI 10.1016/j.solidstatesciences.2010.03.004.

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Abstract

The new compound {[In(C6H14N2)2]2Sb4S8}Cl2 was prepared under solvothermal conditions reacting InCl3, Sb and S using 1,2-trans-diaminocyclohexane as solvent and structure directing molecule. The compound crystallizes in the monoclinic space group C2/c with a = 29.0259(12), b = 6.7896(2), c = 24.2023(12) Å, β = 99.524(4)°, V = 4703.9(3) Å3. The central structural motif is the thioantimonate(III) anion [Sb4S8]4− acting as a tetradentate ligand thus joining two symmetry related In3+ centered complexes. This binding mode was never observed before for the [Sb4S8]4− anion. The optical band gap was determined as 2.03 eV in agreement with the red color of the compound. The thermal decomposition was monitored with in-situ X-ray diffraction experiments. After the emission of the amine molecules an amorphous intermediate is formed followed by the crystallization of InSbS3 which is stable up to about 590 °C. On further heating, InSbS3 is destroyed and reflections of γ-In2S3 appear being contaminated with some elemental Sb. Temperature dependent in-situ X-ray powder diffractometry performed between 30 and 220 °C reveals an unusual reversible negative and positive thermal expansion. The decrease of the a-axis in the temperature range is about 0.74 Å and the increase of the c-axis ca. 0.54 Å. Interestingly, the b-axis exhibits also a thermal expansion, i.e., a biaxial positive and an uniaxial negative thermal expansion coexist which is very unusual. The relative negative expansion coefficients for the a-axis of −194 × 10−6K−1 (30–120 °C) and −82 × 10−6K−1 (120–220 °C) are in the region of so-called colossal thermal expansion.

Document Type:	Article
Research affiliation:	Kiel University > Kiel Marine Science OceanRep > The Future Ocean - Cluster of Excellence Kiel University
Refereed:	Yes
Open Access Journal?:	No
Publisher:	Elsevier
Projects:	Future Ocean
Date Deposited:	12 Jun 2018 11:19
Last Modified:	28 Mar 2019 11:59
URI:	https://oceanrep.geomar.de/id/eprint/43358

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