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MÖSSBAUER EMISSION SPECTRA OF
57Co-LABELLED COBALT SALTS OF HEXACYANO- AND PENTACYANONITROSYL-METALLATES
M. Takeda, K. Ohki, H. Wei, T. Tominaga, N. Saito
To cite this version:
M. Takeda, K. Ohki, H. Wei, T. Tominaga, N. Saito. MÖSSBAUER EMISSION SPECTRA OF 57Co-LABELLED COBALT SALTS OF HEXACYANO- AND PENTACYANONITROSYL- METALLATES. Journal de Physique Colloques, 1974, 35 (C6), pp.C6-339-C6-341.
�10.1051/jphyscol:1974658�. �jpa-00215815�
JOURNAL DE PHYSIQUE Colloque C6, supplkment au no 12, Tome 35, Dicembre 1974, page C6-339
MOSSBAUER EMISSION SPECTRA OF 7Co-LABELLED COBALT SALTS OF HEXACYANO- AND PENTACYANONITROSYEMETALLATES
M. TAKEDA, K. OHKI, H. H. WEI, T. TOMINAGA and N. SAITO
Department of Chemistry, Faculty of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
R6sumk. - On a fait une Btude par effet Mossbauer des Btats chimiques de 57Fe produits dans une sBrie de complexes polynuclCaires marques par 57Co2+ de formule KI 57C0m[M(CN)6]n, xH2O (M = Fe(11, 111), Co, Mn, Cr) et KI 57Co[M(CN)5NO], xH2O (M = Fe, Mn) prksentant des ponts cyanure de la forme -57Co-N-C-M-. On a trouvB que les atomes de 57Fe formb sont stabilisks dans 1'6tat spin fort Fez+ ou Fe3+ environ 10-7 s apres la dbsintegration.
Abstract. - We have investigated by Mossbauer spectroscopy the chemical states of 57Fe produced in a series of 57Co2+-labelled polynuclear complexes of the formula, KI 57C~m[M(CN) 6]n. xH20 (M = Fe(I1, 111), Co, Mn, Cr) and K1 57Co[M(CN)sNO] .xH20 (M = Fe, Mn), which have bridging CN groups of the form --57Co-N--C-M-. The 57Fe atoms formed were found to be stabilized in the high-spin Fez+ or Fe3+ state at approximately 10-7 s after the decay event.
1. Introduction.
-
Transition metal salts of hexa- cyano-metallates have cubic lattice st~uctures possessing bridging CN groups of the form --MI-N=C-M-.Mossbauer emission spectroscopic studies have been made recently of the chemical states of the 57Fe atoms formed by the 57Co
5
57Fe process in the 57Co- labelled hexacyano-cobaltate4111) of metal ions such as Mn2+, Fez+, Co2+, N12+, Cu2+, Zn2+, Cd2+, and Fe3+, which have the -M'-N=C-57Co(III)-linkage [I, 21. It has been made clear that (1) as well as Fe(II1) (cN):-, the new 57Fe labelled species, tenta- tively identified as Fe(1II) (cN):- [I] or Fe(II1) (CN),X [2], are present as minor components in the hexacyano-cobaltates(II1) of the metal ions other than Fe2+, and the relative yield of the new species varies with the kind of metal ions [2] and (2) in the com- plex with the - ~ e ~ + -N= C- 57Co(III)- linkage, not Fe(II1) (cN)~-, but Fe(I1) (cN)~- is produced [I, 21.
However, such systematic study has not yet been done of the chemical states of the 57Fe atoms produced in the 57Co-labelled complexes having the -57C02+-NsC-M- linkage, although some MBssbauer emission studies have been done on such 57C02+-labelled or doped polynuclear transition metal complexes as 57Co,[Co(CN)6]z. 12 K 2 0 [3], K257Co[Fe(CN)6].xHz0 [4], 57C02+ doped KFe3+("co) [Fe(II) (CN),] . x H 2 0 [5], and 57C02+/
[Fe(CN),I4-and 57C02 + /[Fe(CN),I3- [61.
The present investigation was undertaken to eluci- date the chemical states of the 57Fe atoms produced by EC decay and to compare the chemical effects in a series
of 57C02+-labelled complexes of the formula, K, 57Co,[M(CN)6],,
.
xH,O (M = Fe(II), Fe(III), Co(III), Mn(III), Cr(II1)). The polynuclear complexes K, 57Co[M(CN)5NO] . x H 2 0 (M = Fe, Mn), also having the 57C02+ -N = C-M- linkage, were also investigated.2. Experimental. - 57C02+-labelled polynuclear complexes were prepared by using 0.5
-
2 mCi of 57Co.The characterization of the compounds was carried out by chemical analyses on the corresponding non- labelled complexes prepared by the same procedure.
X-ray powder patterns, IR spectra and Mossbauer absorption spectra (for the compounds containing iron) were measured and it was confirmed that the Co2+ ion is bound to the N end of the cyanide ion.
The Mossbauer emission spectra were measured by means of a Hitachi AA-40 Mossbauer spect, rometer with a moving source of the labelled complexes kept at 80 K. K4Fe(CN), . 3 H,O made with isotopically enriched 57Fe [7] was used as an absorber, which was kept at 295 K.
3. Results and discussion.
-
The Mossbauer emis- sion spectrum of K2 57Co[Fe(CN),] .2 H 2 0 is shown in figure 1. A strong peak with the isomer shift 6 =+
0.6 mm/s (relative to 310SS at room tempe- rature) is attributed to the high-spin Fe3+ ions pro- duced in the labelled complex. A doublet with the peaks at-
2.4 mm/s and at+
0.2 mm/s shows the presence of high-spin Fez+ ions as a minor component. The anhydrous salt gave the same emission spectrum asArticle published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1974658
C6-340 M. TAKEDA, K. OHKI, H. H. WEI, T. TOMINAGA AND N . SAITO
FIG. 1. - Mossbauer emission spectrum of Kz ~ ~ C O [ F ~ ( C N ) ~ ] . ~ H z 0 at 80 K.
-4
-
2 0 2 4 mmlsthat of the hydrate. The absence of an observed effect of water molecules on the chemical states of 57Fe atoms formed by EC decay may be partly due to the zeolitic nature of the water molecules. It is interesting to note that the proportion of the 57Fe2+ high-spin species formed is larger in K,co(~~co) [Fe(II) (CN),] . x H 2 0 (x = 0,2) studied here than in 57Co-doped KFe(57Co) [Fe(II) (CN),]
.
H 2 0 studied by Fenger et aE. [5], in which 57C02+ is located at the same octahedral nitro- gen coordinated site as the Fe3+, although a large proportion of the 57Fe atoms are stabilized as high- spin Fe3+ ions in both 57Co-labelled or -doped complexes.The Mossbauer emission spectrum of
(Fig. 2) shows that most of the 57Fe atoms are stabi- lized as high-spin Fez+ species (6 =
+
1.3 mm/s,FIG. 2. - Mossbauer emission spectrum of K ~ ~ C O [ C O ( C N ) ~ ] .xH20 at 80 K.
AEQ = 2.4 mm/s). The similar spectrum was observed by Sano and-Herber [3] for 57~03[Co(CN)6]2. 12 H20.
The emission spectrum of K 57Co[Fe(CN)6] .xHzO (Fig. 3) exhibits two peaks due to the quadrupole splitting of 0.5 mm/s. The isomer shift of
+
0.6 mm/s indicates the formation of high-spin Fe3 + ions.57C03[Mn(CN)6] .xH2O gave the similar spectrum to that of K, 57Co[Fe(C~)6].2 H20. The spectrum indicated that a large proportion of the iron atoms are stabilized as Fe3+ high-spin ions and that Fez+ high- spin species are also present in minor proportion.
VELOCITY
RG. 3.
-
Mossbauer emission spectrum of K s7C~[Fe(CN)6] .xHzO at 80 K.The Mossbauer emission spectrum of
demonstrated clearly most of the 57Fe atoms are stabilized as Fez+ high-spin ions with 6 =
+
1.2 mmfs and A E - 2.6 mm/s.Q
7
The emission spectra of
and
K
57Co[Mn(CN)5NO]. xHzO showed that a large proportion of the 57Fe atoms are stabilized as Fez+ions, whose Mossbauer parameters are 6 =
+
1.4 mm/s,AEQ = 2.6 mm/s for the former and 6 =
+
1.3 mm/s, AEQ = 2.6 mm/s for the latter. The shoulder appearing on the peak with more positive velocity may suggest that high-spin Fe3+ ions are present as minor com- ponents.The large linewidth of 0.7
-
1.3 mm/s may indi- cate that the iron ions produced in each labelled compound are located in various, slightly different surroundings, possibly due to the damage caused by the decay process.We have drawn the following conclusion from the experimental results. At about s after EC decay of
5 7 ~ ~ 2 +
,
most of the 57Fe ions produced in these compounds are stabilized as high-spin Fez+ or Fe3+. The distribution of the Fez+ or Fe3+ ions is as follows : Fe3+ only in K 57Co[Fe (III)(CN),] .xHzO ; mainly Fe3+ with some Fe2+ inand 57C03[Mn(III) (CN),],
.
xHzO ; mainly Fe2 + with some Fe3+ in K 57Co[Cr(III) (CN),] .xH20, K 57Co[Mn(I) (CN),NO] .xHzO andFez' only in K 57Co[Co(III) (CN),]
.
xH20. Alekseev et al. 161 have revealed by time-dependent MossbauerMOSSBAUER EMISSION SPECTRA OF 57Co-LABELLED COBALT SALTS OF HEXACYANO C6-341
technique that some 57Fe atoms produced in the system of 57C02+ /[Fe(CN),I3 - are stabilized as Fez + ions at first, after neutralization, and then the state changes to the stable system Fe3+/[Fe(CN),I4- through intramolecular electron transfer. Therefore, the formation of anomalous Fe3+ ions in the complexes studied is possibly due to the chemical oxidation reac- tion of the Fez+ ions, formed through the charge neutralization process, by the surrounding species within a time scale of s. No evidence
was found on the formation of low spin species such as [57Fe(CN),] from high-spin species such as [57Co(N~-)6].
Acknowledgment.
-
The authors wish to thank Dr. F. Ambe of the Institute of Physical and Chemical Research for his kind assistance in the Mossbauer measurements. We also acknowledge the assistance of Miss T. Got6 and Mr. A. Yasuda with the experi- mental work.References
[I] FENGER, J., SIEKIERSKA, K. E. and OLSEN, J., J. Chem. Soc. Effects of Nuclear Transformations, Cambridge, July
Dalton (1973) 563. 1969, p. 69.
[2] PRUSAKOV, V. E., STUKAN, R. A., BORSHAGOVSKII, B. V., [51 FENGER, J.7 MADDOCK¶ A. G. and SIEKIERSKA~ K. E.* J.
GOL'DANSKII, V. I., Teor. Eksp. Khim. 9 (1973) 707. Chem. Soc. (A) (1970) 3255.
[6] ALEKSEEV, V. P., GOL'DANSKII, V. I., PRUSAKOV, V. E., [3] SANO, H. and HERBER, R. H., Fourth International Hot Atom NEFED'EV, A. V. and STUKAN, R. A., Pis'ma Zh. Eksp.
Chemistry Symposium, Kyoto, Japan (1967). Teor. Fit. 16 (1972) 65.
[4] SAITO, N., TAKEDA, M., OHKI, K., WEI, H. H. and TOMI- [7] SAITO, N., TAKEDA, M. and TOMINAGA, T., Radiochem.
NAGA, T., Chemical Society Symposium on Chemical Radioanal. Letters 6 (1971) 169.
