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Title: Structure Characterization and Properties of K-Containing Copper Hexacyanoferrate

Copper hexacyanoferrate, CuII[FeIII(CN)6]2/3 nH2O, was synthesized, and varied amounts of K+ ions were inserted via reduction by K2S2O3 (aq). Ideally, the reaction can be written as CuII[FeIII(CN)6]2/3∙ nH2O + 2x/3K+ + 2x/3e⁻ ↔K2x/3CuII[FeIIxFeIII1- x(CN)6]2/3 nH2O. Infrared, Raman, and Mössbauer spectroscopy studies show that FeIII is continuously reduced to FeII with increasing x, accompanied by a decrease of the a-axis of the cubic F$$m\bar{3}$$m unit cell. Elemental analysis of K by inductively coupled plasma shows that the insertion only begins when a significant fraction, ~20% of the FeIII, has already been reduced. Thermogravimetric analysis shows a fast exchange of water with ambient atmosphere and a total weight loss of ~26 wt % upon heating to 180 °C, above which the structure starts to decompose. The crystal structures of CuII[FeIII(CN)6]2/3∙ nH2O and K2/3Cu[Fe(CN)6]2/3∙ nH2O were refined using synchrotron X-ray powder diffraction data. In both, one-third of the Fe(CN)6 groups are vacant, and the octahedron around CuII is completed by water molecules. In the two structures, difference Fourier maps reveal three additional zeolitic water sites (8c, 32f, and 48g) in the center of the cavities formed by the Cu N C Fe framework. In conclusion, the K-containing compound shows an increased electron density at two of these sites (32f and 48g), indicating them to be the preferred positions for the K+ ions.
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  1. Stockholm Univ. (Sweden). Dept. of Materials and Environmental Chemistry
  2. Uppsala Univ. (Sweden). Dept. of Chemistry, Angstrom Lab.
  3. Julich Research Centre (Germany). Julich Centre for Neutron Science (JCNS). Peter Grunberg Inst. (PGI), Forschungszentrum Juelich GmbH
  4. Julich Research Centre (Germany). Julich Centre for Neutron Science (JCNS). Peter Grunberg Inst. (PGI), Forschungszentrum Juelich GmbH; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 55; Journal Issue: 12; Journal ID: ISSN 0020-1669
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Swedish Research Council VR
Country of Publication:
United States