HYPERFINE INTERACTIONS AND MAGNETIC MOMENTS OF SOME Fe(II) COMPLEXES WITH DIMETHYLFORMAMIDE AND DIMETHYLTHIOFORMAMIDE

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HYPERFINE INTERACTIONS AND MAGNETIC MOMENTS OF SOME Fe(II) COMPLEXES WITH

DIMETHYLFORMAMIDE AND DIMETHYLTHIOFORMAMIDE

G. Wiesinger, G. Gritzner, W. Linert

To cite this version:

G. Wiesinger, G. Gritzner, W. Linert. HYPERFINE INTERACTIONS AND MAG- NETIC MOMENTS OF SOME Fe(II) COMPLEXES WITH DIMETHYLFORMAMIDE AND DIMETHYLTHIOFORMAMIDE. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-293-C1-294.

�10.1051/jphyscol:19801104�. �jpa-00219585�

JOURNAL DE PHYSIQUE CoNoque C1, suppl6rnent au n

"

(21-293

HYPERFINE IMERACTIONS AND WGNETIC

OF S M

COMPLEXES WITH DIMETHYLFORMAMIDE AND DIMRHYLTHIOFORMAMIDE

G. Wiesinger, G. Gritzner

+

+

Institut fUr ExperimentaZphysik, 2'.

U. Vienna, Austria.

+

U. Vienna, Austria.

The aim of the present investigation w a s to gain i n f o n a t i o n on the d i f f e r e n t interactions of trans- i t i o n metal cations with ligands that exhibit t h e i r donor properties v i a an oxygen and a sulphur a t m respectively. Model substances to study these interactions have been prepared from Fe( 11) com- plexes and NN dimethylfomanide (D1vIF) as well as NN d i m e t h y l t h i o f o m i d e (DIWF). The following ccmpounds were obtained:

F ~ ( D M F ) ~ ( C ~ O ~ ) ~ F~(DIVTPF)~(C~O~)~

Fe(DMF)2C12 Fe(DITl!F)2C12

Fe (DMF) B r 2 Fe (DC4TF) 2Br2

Fe(DMF')312 Fe (DLWF )

In the present discussion emphasis is l a i d on re- s u l t s fkwn MGssbauer and magnetic measurements.

Additional experiments which have been performed during this work, i.e. structure determination, optical spectroscopy, and e l e c t r i c a l conductivity measurement w i l l be published elsewhere /I, 2/.

The 5 7 ~ e Mijssbauer experiments have been carried out i n the temperature range between 4.2 K and 200 K. It is c m o n to all these compounds that they exhibit a relatively low me1 ting point (-400 K).

A s a consequence they have a low Debye temperature and therefore the r e c o i l f r e e fraction is vanishing above-200 K. The spectra were f i t t e d using a l e a s t squares f i t procedure assuming a super- position of Lorentzian l i n e s /3/. With one ex- ception only pure doublets were obtained. The re- s u l t i n g hyperfine parameters are l i s t e d in table 1:

TABLE 1: Hyperfinc parameters a t T = 4.2 K

DMF IS( SFP) A(2

[ m / s e c

2

+_

(c104)2 1.62 2.58/2.02

C12 1.56 3.36

'jr2 1.55 3.15

I 2 0.91 3.77 (80 K )

DMTF

(C104)2 1.26 3.33

C12 1.20 3.11

Br2 1.14 5.31

I2 1.13 3.45 (80 K)

Magpetic susceptibility rrleasurernents were carried out by means of a Faraday balance (77 K c T < 300 K, H <12 kG), the f i e l d dependence of Lhe magneti-

apP

sation was investigated using an e x t r a z t i o ~ magneto- -.eter (4.2 K < T < 300 K , H

<

apFl

table 2 show "hat all the complexes are high spin.

TABLE 2: Effective magnetic mments a t T = 300 K p e f f l p B J

DMF DMTF

( c104) 2 5.11 5.17

C12 5.48 5.41

nr2

-

I2

-

Besides F ~ ( C ~ O ~ ) ~ ( D M F ' ) ~ similar r e s u l t s with re- spect t o Ivrdssbauer and magnetic measurements were obtained f o r a l l cmplexes. The magnetic suscepti- b i l i t y exhibits a Curie l i k e behaviour. F i r s t re- s u l t s frcm structure determination indicate t h a t

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801104

C 1-294 JOURNAL DE PHYSIQUE

i n the (C10 4 2 ) cmplexes Fe is surrounded by a s l i g h t l y d i s t o r t e d octahedron / 2 / , whereas electron t r a n s i t i o n spectroscopy .nleasurements vake a tetra- hedral surrounding f o r the other complexes more l i k e l y /I/. Ghadrupole s p l i t t i n g and the isomer s h i f t d a t a deduced f m M'ossbauer s p e c t r a show the usual Fe(I1) high spin values. The quadrupole interaction decreases s l i g h t l y with temperature l h i c h can be a t t r i b u t e d to the thennal population of low lying o r b i t a l s . Contrary to all the other cornplexes discussed i n t h i s paper the Mossbauer spectra of Fe(C104)2DMF'6 show a four l i n e p a t t e r n with a temperature dependent, i n t e n s i t y r a t i o of the two quadmpole doublets ( table 1, f i g . 1)

.

viously the surrounding of the ~ e ion undergoes ~ + a transformation with temperature, which is a l s o evident by a di scon tintri ty in the 1 / X (T) curve ( f i g . 2). However the t r a n s i t i o n is not a ccmplete one. Similar r e s u l t s have been published already /4-7/. To decide whether only the octahedral sur- rounding o r the whole c r y s t a l s t r u c t u r e is changed, low temperature x-ray d i f f r a c t i o n experiments are planned.

ACI(NOW1lDGEMENTS

This 1ror-k p a r t l y supported by the Fonds zur Fordenmg d e r wissenschaftlichen Forschung

(Fontrac t N r . 3004).

REFERENCES

/I/ W. Linert, Diplmarbeit, T.U. Wien; G. Gritz- ner, W. Linert, t o be published.

/2/ A. Bamgartner, Monatshefte der Chemie, t o be published.

/3/ W. Kijndig, Phcl. I n s t r . Meth.

2

/4/ P.J. Ouseph, P.M. Thomas, I. Deszi, J. Phys.

Chem. Sol.

2

/5/ R. Latorre, C.R. Abeldo, R.B. Frankel, J.A.

Costamagna, W.M. Reiff, E. Frank, J. Chem.

Phys.

59

/6/ R.Latorre, J . Costamagna, P. Navia, J. Phys.

(Paris)

37

/7/ W.M. Reiff, R.B. Frankel, C.R. Abeldo, Chem.

Phys. Lett.

22

Fe(DMF)6(C104)2

FIG. 1.

-

[

-

of the two phases -3s. s u s c e p t i b i l i t y vs.

temperature temperature