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Submitted on 1 Jan 1979
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MÖSSBAUERE MISSION SPECTRA OF
57Co-LABELLED BIS - (β -DIKETONATO) Co (II) DIHYDRATE
H. Wei
To cite this version:
H. Wei. MÖSSBAUERE MISSION SPECTRA OF 57Co-LABELLED BIS - (β-DIKETONATO) Co (II) DIHYDRATE. Journal de Physique Colloques, 1979, 40 (C2), pp.C2-426-C2-427.
�10.1051/jphyscol:19792149�. �jpa-00218522�
JOURNAL DE PHYSIQUE Coiioque C2, suppl6ment au no 3, Tome 40, mars 1979, page C2-426
M~SSBAUER
EPlI SSION SPECTRA O F 5 7 ~BIS-(0-DIKETONATO)
~ - ~ CO(I I) DIHYDRATE
~ ~ ~ ~ ~ ~ ~H.H. Wei
Department of Chemistry, Tamkang College of A r t s and S c i e n c e s , Tamsui, Taiwan, Republic of China
Rdsum6.- Les Qtats chimiques du 5 7 ~ e apparaissant dans 5 7 ~ o (11) (R'COCHCOR")22H20 ont Btd dtudids par effet MEssbauer (R' ou R" = CH3, CF3, C6Hs et CH30). L'examen des spectres d'dmission G s s - bauer P 78 K montre que l'effet du substituant
B
sur la fraction de Fe3+ produit dans les complexes marquds de 5 7 ~ o est corrdld 1 l'dlectrondgativitd du groupement (CH30 > CF3 > CsH5 > CH3)gj De plus, les paramstres Mgssbauer des atomes de fer divalents dans les complexes marquds de CO sont trSs proches de ceux observds dans des expdriences d'absorption sur les composds ferreux corres- pondants.Abstract.- The chemical states of 5 7 ~ e atoms produced in 5 7 ~ o ( ~ ~ ) (R' COCHCOR")22H20 (where R' or R" = CH3, CF3, C6H5 and CH30) were investigated by means of ~ijssbauer spectroscopy. According to the Mijssbauer emission spectra at 78 K, it was found that the 6-substituent effect on the fraction of ~ eproduced in the 57~o-labelled ~ + complexes was related to the order of group electronegativi- t i.e. CH30 > CF3 > C6Hs > CH3. In addition, the ~Essbauer parameters of divalent iron atoms in 5yCo-labelled complexes are very close to those observed in the abosrption experiments with the corresponding ferrous compounds.
1. Introduction.- ~&ssbauer emission spectroscopic studies of 57~o-labelled tris (B-diketonato)Co(III) have been made by several workers 11-61 and the charge states of iron atoms in the complexes are found to be Fe3+ and Fe2+ states. The ratio of Fe2+/
Fe3+ is correlated to the y-substituent of $-dike- tonato ion 151. However, no experimental results have been reported on the Mijssbauer emission spec- troscopy with substituted 57~o-labelled cobalt(I1) B-diketonato dihydrate. It has been recognized that the presence of water ligand favors the stabiliza- tion of Fe3' species produced in 57~o-labelled hydrated Co(I1)-complexes.
The present investigation was undertaken to elucidate the effect of water ligand and B-substi- tuent of the diketonato ion on the chemical states of the 5 7 ~ e atoms produced by EC decay of 5 7 ~ o in bis (B-diketonato) Co(I1) dihydrate, also to compa- re the ~Zssbauer parameters of the 57~o-labelled complexes with those of corresponding iron(I1)- complexes,
2. Experimental
.-
57~o-labelled Co(I1) (R' COCHCOR") 22H20 were prepared by the method similar to that of non-radioactive cobaltous complexes as described in the literature /7/, but about 2mCi of a carrier free 5 7 ~ o ~ 1 2 solution was added to the methaaolic solu- tion of cobaltous chloride before the addition of the other reagent. The ferrous complexes were pre- pared according to the method reported in the literature 18-91. The characterization of the co- balt and iron compounds was carried out by chemical
analysis and IR spectra.
The MEssbauer emission spectra were measured by a constant acceleration type spectrometer with a
source of the labelled complexes kept at 78 K.
57~e-enriched K+Fe(CN)63H20 was used as absorber.
The MEssbauer spectra of ferrous compounds were observed with 5 7 ~ o ( ~ ~ ) as source. The isomer shift I.S.) was taken with respect to the centroid of the potassium ferrocyanide.
3. Results and discussion.- The MEssbauer emission spectra of 5 7 ~ o ( ~ ' ~ ~ ~ ~ ~ ~ ~ " ) 2 2 ~ 2 0 at 78 K are shown in Figure 1. The ~Essbauer parameter of ferrous species in the 57~o-complexes and ferrous compounds are listed in Table I.
Table I : Mijssbauer Parameters of Ferrous iron ir the Complexes at 78 K.
Isomer shifts Quadrupole splittings (mm1 S) (mm/s)
57~o(acac)22~~0 1.35 2.68
( 1 ~34) (2.68)
It is found that with the exception of 3 7 ~ o (acac)22H20, the spectra show the existence of two kinds of emission lines, one is characteristic of
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792149
the high-spin ~ e * + state and the other of the high- spin ~ e state. The yield of ~~ + e species produced ~ + in 57~o-labelled complexes has the order of CH30 (%45 %) > CF3 (%35
X)
> CsHs(%25 %),
CH3 (W %) .ThGorder is related to the order of group electronega- tivity of CH30(3.7) > CF3(3.35) > CsH5(3.0) > CH3 (2.3) /10/.
Fig. 1 : Mijssbauer emission spectra of 57~o-labelled bis- (B-diketonato)Co(II)dihydrate at 78 K.
The brackets stand for the I.S. and Q.S.
for corresponding ferrous compounds.
acac = acetylacetonate (CH3COCHCOCH3), dbm = dibenzoylmethane (CsH5COCHCOCsH5), hfa = hexafluoroacetylacetonate (CF3COCHCOCH3), meoac = methoxyacetoacetate (CH30COCHCOCH3).
One would then conclude that the less elec- tron density at oxygen atom of carbonyl group in B-diketonato ligand makes the site more favorable for a trivalent iron atom, which is in accord with inductive effect. This dominant factor also appears to play an important role in the action of decrea- sing and increasing the isomer shift of ferrous ion
for 57~o-labelled cobalt compounds and corresponding ferrous compounds. In addition, the values of the isomer shifts and quadrupole splittings of divalent ferrous species produced in 57~o-labelled complexes are very close to those observed in the absorption experiments with corresponding ferrous complexes.
This observation demonstrates that the chemical en- vironment around iron atoms produced from 5 7 ~ o at about 10-~s after EC decay is similar to that in the corresponding ferrous compounds.
Acknowledgment.- The author wishes to express his sincere gratitude to Professor Nobufusa Saito for his encouragement and guidance. Thank is extended to Dr. Masuo Takeda, The University of Tokyo forhis help and technical assistance.
References
/ I / Wertheim, G.K., Kingston, W.R. and Herber, R.H.
J. Chem. Phys.,
37
(1962) 687./2/ Hazony, H. and Herber, R.H., J. Inorg. Nucl.
Chem.,
2
( 1969) 32 1.131 Friedt, J.M., Baggio-Saitovitch, E. and Danon, 3. Chem. Phys. Lett.
2
(1970) 603.141 Sano, H. and Iwagami, H., Chem. Commun., (1971) 1637.
151 Afanasov, M.I., perfile$, Yu. and Babeshkin,A.M.
J. Radioanal. Chem.,
7
(1975) 125.161 Sano, H., J. Radioanal. Chem.
36
(1977) 105.171 Charles, R.G., and Pawlikowskii,M.A., J. Phys.
Chem.,
62
(1958) 440.181 Buckingham, D.A., Cheong, J.L.E., Fergusson, J.E. and Wilkins, C.J., J. Chem. Soc., (1963) 3461.
/g/ Buckingham, D.A. and Henry, J.A., Australian J. Chem., (1967) 497.
/10/ Gillion, R.D., "Introduction to Physical Orga- nic Chemistry", Addison Wesley Publishing Com- pany, (1970) 146.
