Syntheses, Structure, and a Mössbauer and Magnetic Study of Ba4Fe2I5S4

详细信息    查看全文

• 作者：Danielle L. Gray ; Gary J. Long ; Fernande Grandjean ; Rapha&euml ; l P. Hermann ; James A. Ibers
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：January 7, 2008
• 年：2008
• 卷：47
• 期：1
• 页码：94 - 100
• 全文大小：190K
• 年卷期：v.47,no.1(January 7, 2008)
• ISSN：1520-510X

文摘

The compound Ba₄Fe₂I₅S₄ has been prepared at 1223-1123 K by the "U-assisted" reaction of FeS, BaS, S, andU with BaI₂ as a flux. A more rational synthesis was also found; however, the presence of U appears to beessential for the formation of single crystals suitable for X-ray diffraction studies. Ba₄Fe₂I₅S₄ crystallizes in a newstructure type with two formula units in space group I4/m of the tetragonal system. The structure consists of a Ba-Inetwork penetrated by chains. Each Fe atom, which is located on a site with symmetry, is tetrahedrallycoordinated to four S atoms. The FeS₄ tetrahedra edge-share to form linear chains in the [001] direction.The Fe-Fe interatomic distance in these chains is 2.5630(4) Å, only about 3% longer than the shortest Fe-Fedistance in -Fe metal. Charge balance dictates that the average formal oxidation state of Fe in these chains is+2.5. The Mössbauer spectra obtained at 85 and 270 K comprise a single quadrupole doublet that has hyperfineparameters consistent with an average Fe oxidation state of +2.5. The Mössbauer spectrum obtained at 4.2 Kconsists of a single magnetic sextet with a small hyperfine field of -15.5 T. This spectrum is also consistent withrapid electron delocalization and an average Fe oxidation state of +2.5. The molar magnetic susceptibility of Ba₄Fe₂I₅S₄, obtained between 3.4 and 300 K, qualitatively indicates the presence of weak pseudo-one-dimensionalferromagnetic exchange within a linear chain above 100 K and weak three-dimensional ordering between thechains at lower temperatures.