Structure Characterization and Properties of K-Containing Copper Hexacyanoferrate.
Copper hexacyanoferrate, Cu(II)[Fe(III)(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 Cu(II)[Fe(III)(CN)6]2/3·nH2O + 2x/3K(+) + 2x/3e(-) ↔ K2x/3Cu(II)[Fe(II)xFe(III)1-x(CN)6]2/3·nH2O. Infrared, Raman, and Mössbauer spectroscopy studies show that Fe(III) is continuously reduced to Fe(II) with increasing x, accompanied by a decrease of the a-axis of the cubic Fm3̅m unit cell. Elemental analysis of K by inductively coupled plasma shows that the insertion only begins when a significant fraction, ∼20% of the Fe(III), 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 Cu(II)[Fe(III)(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 Cu(II) 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. 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.
Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-10691 Stockholm, Sweden.
Dickson O
DO
Ojwang
Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-10691 Stockholm, Sweden.
Jekabs
J
Grins
Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-10691 Stockholm, Sweden.
Dariusz
D
Wardecki
Department of Chemistry, Ångström Laboratory, Uppsala University , Box 538, SE-75121 Uppsala, Sweden.
Mario
M
Valvo
Department of Chemistry, Ångström Laboratory, Uppsala University , Box 538, SE-75121 Uppsala, Sweden.
Viktor
V
Renman
Department of Chemistry, Ångström Laboratory, Uppsala University , Box 538, SE-75121 Uppsala, Sweden.
Lennart
L
Häggström
Department of Chemistry, Ångström Laboratory, Uppsala University , Box 538, SE-75121 Uppsala, Sweden.
Tore
T
Ericsson
Department of Chemistry, Ångström Laboratory, Uppsala University , Box 538, SE-75121 Uppsala, Sweden.
Torbjörn
T
Gustafsson
Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH , D-52425 Jülich, Germany.
Abdelfattah
A
Mahmoud
Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH , D-52425 Jülich, Germany.|Materials Science and Technology Division, Oak Ridge National Laboratory , Oak Ridge, 37831 Tennessee, United States.
Raphaël P
RP
Hermann
Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-10691 Stockholm, Sweden.
Gunnar
G
Svensson