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Submitted on 1 Jan 1979
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STRUCTURE OF COBALT FERRICYANIDE
K. Fukumura, T. Kobayashi
To cite this version:
K. Fukumura, T. Kobayashi. STRUCTURE OF COBALT FERRICYANIDE. Journal de Physique
Colloques, 1979, 40 (C2), pp.C2-373-C2-374. �10.1051/jphyscol:19792131�. �jpa-00218503�
JOURNAL DE PHYSIQUE Colloque C2, supplkrnent nu n
"
3, Tome 40, mars 1979, page C2-373STRUCTURE OF COBALT FERRI CYAN I DE
K. Fukumura and T. Kobayashi
Medical C o l l e g e of S h i g a , Otsu, S h i g a , 520-21 Japan
R6surnQ.- La structure et la stabilitC de C O ~ + ~ ~ ( C N ) ~ ~ - autour de la temperature ambiante ont QtQ Qtudides par spectrom6trie Mossbauer et diagramme de poudre R-x. On observe un passage de ferri- cyanure au ferrocyanure quand 116chantillon chauffQ estrefroidi 2 l'air.
Abstract
.-
Using Mijssbauer spectroscopy and X-ray powder diffraction, the structure of Co2+B e (CN) and its stability have been investigated around room, temperature. We have gotten a result t at the stability of ferrocyanide formed by heating cobalt ferricyanide depends on whether the sample is heated under vacuum or in air.
Using Msssbauer emission spectroscopy with CO~+F~(CN)~I]~-, Alekseev et al. /I/ have observed charge states of Fe2+ and Fe3+, and explained this fact on the basis of the intramolecular electron transfer reaction. We have found for this material that the yields of Fe2+ and Fe3+ have temperature- dependences, even when the spectrum is taken at room temperatures (from -10'~ to 40'~); the yield of Fe2+
decreases with temperature increased. We presume that the change of yields with temperature is attributed
to instability of the structure of
CO~+P~(CN)~I]~-.
In the present paper, we investigate, by using Mb'ss- bauer spectroscopy and X-ray powder diffraction, the structure of Co2+Pe(CN)6I]'- and its stability around room temperature.
co2+Ee(CN) 3- was prepared by mixing 0.01N solution of
K~P~(CN)~I]:
having a pH of 2 and 0.01N solution of CoC12. After crystalization for 10hours, the precipitation was washed with distil- led water and ethyl alcohol, and then dried. A part of the sample powder was heated at 150°C for 3 hours in an evacuated glass ampule and left unsealed in air for 5 months. This procedure gives the powder a change of colour from brown to dark green. X-ray diffraction patterns with Cu KCY X-radiation and Msssbauer absorption spectra were taken with the heated and unheated samples.In table I are shown the parameters obtai- ned by the Mossbauer spectroscopy. We get, from the spectrum of the unheated sample, the typical values of the isomer shift and quadrupole splitting of
though we cannot interpret why these peaks appear.
The result of measurements with this sample indicates that most to the ferricyanide ions in Co2+[Fe(~~)d3- change to ferrocyanide ions by heating at 150°C under vacuum and are stabilized. The lattice constant
10.24 A of the unheated sample obtained by other workers /2,4/.
Table I. ~Essbauer parameters
Sample Isomer Shift Quadrupole Yield Splitting
- -
(mm/ s (mmls)-
(%I (a) Fe I11 -0. I I 0.78 100.0 (b) Fe I1-0.03 - 70.7
Sample temperature is 80K in all measurements.
(a) denotes the unheated sample, (b) the sample heated at 1 5 0 ~ ~ under vacuum, (c) the sealed sam- ple and (d) the unsealed sample.
(n) Doublets are assumed to be Fe3+
We get a numerical value of the lattice constant for the sample heated at 150°C as 10.02 A, ferricyanide ions /2,3/. The spectrum of the sample
which is different from that of co2+
E~(cN) 6T- 121.
heated at 1 5 0 ~ ~ is resolved into a singlet and a
The X-ray diffraction pattern of this sample is c h a doublet. We can ascribe the singlet to the resonan-
racteristic of Co2+
E~(cN)
673-9 however the lattice ce absorption by ferrocyanide ions. The doubletis roba ably attributed to the absortion by Fe3' ions. constant is smaIler than that of Co2*
P~(CN)
In order to get more information about stability of X~etails will be published elsewhere.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792131
C2-374 JOURNAL DE PHYSIQUE
ferrocyanide ions, we took MSssbauer spectra with References samples having both ferri- and ferrocyanide ions in
them. Two samples were made by heating at 120'~; one /I/ Alekseev, V.P., Gol'danskii, V.I., Prusakov, V.E., was sealed, the other was left unsealed in air. The Nefed'ev, A.V. and Stukan, R . S . , Pis'ma Zh. Eksp.
Teor. Fiz.
5
(1972) 65 (JETP Lett. 16 (1972) parameters obtained from the spectra taken after 43).aging for a week are shown in table I. By comparing / 2 / Maer, K. Jr, Beasley, M . L . , Collins, R . L . and the yield of Fe" of the sealed sample with that of Milligan, W.O., J. Amer. Chem. Soc.
90
(1968)3201
.
unsealed one, we recognize a decreasing of ferrocya-
/3/ Fenger, J., Siekierska, K.E. and Olsen, J., J nide ions, when the heated sample is allowed to Chem. Soc. Dalton Trans.
5
(1973) 563.stand in air. Therefore we can say that the stabili- /4/ Wyckoff, R.W.G., "Crystal Structure", Vol. 3, ty of ferrocyanide formed by heating cobalt ferri- (.John Wiley & Sons, New ~ork) 1965, p. 381.
cyanide depends on whether the sample is heated un- der vacuum or in air.
We like to thank Prof. A. Nagasawa and Dr. Y. Matsuo for valuable suggestions and help in X-ray analysis.
