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Ground term crystal field parameters and mössbauer paramagnetic hfs in a spin 32 ironIII complex
CHEMICAL PHYSICS LETTERS
I (1967) 117 - 118. NORTH-HOLLAND
PUBLISHING COMPANY.
AMSTERDAX
AND IM&SBAUER GROUND TERM CRYSTAL FIELD PARAMETERS PARAMAGNETIC HFS IN A SPIN ; IRONHI COMPLEX H. H. WICKMAN
and F. R. M?%tFUTT
Bell Telephone Labo>-alot-ies. Incorporated. Received 1
June
MIIWa~ Hill.
Nex Jersey.
USA
1967
Midssbaucr paramagnctic hfs and EPR studies characterize the ground quartet term in:bis(N. N diisopropyldithiocarbamato) irot@ chloride. The electric interactions of the spin (S = :) and nucleus (iex = 3) are not simply related: the core polarization field from the quartet level is 223(SZ-)kOe.
i Several recent studies of penta-coordinate ironm in bis(N,N-dialkyldithiocarbamato) iron halides have shown the ground electronic state of the iron to be an orbital singlet and spin q&rtet: S = Q, g= 2.00 [l-3]. While one complex is a novel ferromagnet [2], these systems are more commonly paramagnetic to low temperatures [4]. The present
work summarizes
the SH H = @fi-S
o[s,2-J,S2] i- Ef+;ft
S = ? and g = 2.00. A single very broad (AZZmin s 600 Oe) anisotropic line was found and characterized by effective g values (S’ = $) & = 2.03 * 0.05, & = 3.74 + 0.02 and g;1 = 4.21 2 0.02*. Analysis of the angular and temperature dependence of the resonance data and comparison with exact diagonalization of the where
single crystal
EPR and polycrystalline Mijssbauer effect (ME) studies relating to the ground quartet in the representative paramagnetic complex, Fe[diisopropyl DTC]2Cl. The spin Hamiltonian (SH) parameters characterizing the quartet level have been derived from the EPR data. The Mbssbauer paramagnetic hfs shows that the major axis of the crystal field interaction within the S = 4 manifold, and the major axis of the electric field gradient (EFG) at the nucleus, I,, = +, are not simply related. As discussed below, this is equivalent to the statement that in a paramagnet, as in magnetically ordered systems, there need be no
S=+SHga.veD=-4.0=0.50KamiX~E/D= z 0.0362 0.003.The EPR is within the excited doublet (zero field energy -II-) of composition -]&Zs = * $), with g> = 1.99, gi = 3.?5 and g’ = 4.22 for h = 0.036. The ground doublet (at D?l+3h2) has effective gvalues & = 5.99, g& = 0.21 and gi = 0.20. As the ground term is an orbital singlet, an effective paramagnetic hyperfine field is expected from the lower doublet [6]. The resolved ME paramagnetic hfs at 1.2% fig. 1, may be analyzed with the see spin Hamiltonian mentioned above, with the substitutions
simple relation between hyperfine field direction and EFG tensor orientation. The site symmetry of the ironm in the Fe[diisopropyl DTC]$l complex is assumed to be C2v on the basis of available chemical and crystallographic information for the relatti Fe[diethyl DTC]2CI homologue [ 11. The Fe[diisopropyl DTC12Cl complex shows spin only paramagnetism to 0.3oK (measured by the techniques described in ref. [2]). Its &fE&iVe InOXIIt?nt was 3.96 /LB in
coincides with the electronic SH ~-axis. The EFG is expressed with respect to its principal axis system, whose orientation relative to E&f is given by the conventional spherical polar coordinates (D and 8. The Mtlssbauer pattern is reproduced by the parameters ~0= 00, 8 = 9Oo, ($eqQ) = 0.134 * 0.005 cm/set and v = 0.16 = 0.01;
good agreement with the predicted value of 3.88~~ for g = 2.0 and S = $. The chemical details of the sample preparation and crystal growth will be given separately [5]. Within the ground quartet level, EPR was observed (at 24 Gcps) between levels described by June 1967
+
*
117
M.Trozzolo and H. H. Wickman. to be published. Expzrimctiis at 55 Gc were also performed to study the frequency dependence of the observed g values. We are indebted to J.C.Hensel for these measurements.
A.
I (1967) 117 - 118. NORTH-HOLLAND
PUBLISHING COMPANY.
AMSTERDAX
AND IM&SBAUER GROUND TERM CRYSTAL FIELD PARAMETERS PARAMAGNETIC HFS IN A SPIN ; IRONHI COMPLEX H. H. WICKMAN
and F. R. M?%tFUTT
Bell Telephone Labo>-alot-ies. Incorporated. Received 1
June
MIIWa~ Hill.
Nex Jersey.
USA
1967
Midssbaucr paramagnctic hfs and EPR studies characterize the ground quartet term in:bis(N. N diisopropyldithiocarbamato) irot@ chloride. The electric interactions of the spin (S = :) and nucleus (iex = 3) are not simply related: the core polarization field from the quartet level is 223(SZ-)kOe.
i Several recent studies of penta-coordinate ironm in bis(N,N-dialkyldithiocarbamato) iron halides have shown the ground electronic state of the iron to be an orbital singlet and spin q&rtet: S = Q, g= 2.00 [l-3]. While one complex is a novel ferromagnet [2], these systems are more commonly paramagnetic to low temperatures [4]. The present
work summarizes
the SH H = @fi-S
o[s,2-J,S2] i- Ef+;ft
S = ? and g = 2.00. A single very broad (AZZmin s 600 Oe) anisotropic line was found and characterized by effective g values (S’ = $) & = 2.03 * 0.05, & = 3.74 + 0.02 and g;1 = 4.21 2 0.02*. Analysis of the angular and temperature dependence of the resonance data and comparison with exact diagonalization of the where
single crystal
EPR and polycrystalline Mijssbauer effect (ME) studies relating to the ground quartet in the representative paramagnetic complex, Fe[diisopropyl DTC]2Cl. The spin Hamiltonian (SH) parameters characterizing the quartet level have been derived from the EPR data. The Mbssbauer paramagnetic hfs shows that the major axis of the crystal field interaction within the S = 4 manifold, and the major axis of the electric field gradient (EFG) at the nucleus, I,, = +, are not simply related. As discussed below, this is equivalent to the statement that in a paramagnet, as in magnetically ordered systems, there need be no
S=+SHga.veD=-4.0=0.50KamiX~E/D= z 0.0362 0.003.The EPR is within the excited doublet (zero field energy -II-) of composition -]&Zs = * $), with g> = 1.99, gi = 3.?5 and g’ = 4.22 for h = 0.036. The ground doublet (at D?l+3h2) has effective gvalues & = 5.99, g& = 0.21 and gi = 0.20. As the ground term is an orbital singlet, an effective paramagnetic hyperfine field is expected from the lower doublet [6]. The resolved ME paramagnetic hfs at 1.2% fig. 1, may be analyzed with the see spin Hamiltonian mentioned above, with the substitutions
simple relation between hyperfine field direction and EFG tensor orientation. The site symmetry of the ironm in the Fe[diisopropyl DTC]$l complex is assumed to be C2v on the basis of available chemical and crystallographic information for the relatti Fe[diethyl DTC]2CI homologue [ 11. The Fe[diisopropyl DTC12Cl complex shows spin only paramagnetism to 0.3oK (measured by the techniques described in ref. [2]). Its &fE&iVe InOXIIt?nt was 3.96 /LB in
coincides with the electronic SH ~-axis. The EFG is expressed with respect to its principal axis system, whose orientation relative to E&f is given by the conventional spherical polar coordinates (D and 8. The Mtlssbauer pattern is reproduced by the parameters ~0= 00, 8 = 9Oo, ($eqQ) = 0.134 * 0.005 cm/set and v = 0.16 = 0.01;
good agreement with the predicted value of 3.88~~ for g = 2.0 and S = $. The chemical details of the sample preparation and crystal growth will be given separately [5]. Within the ground quartet level, EPR was observed (at 24 Gcps) between levels described by June 1967
+
*
117
M.Trozzolo and H. H. Wickman. to be published. Expzrimctiis at 55 Gc were also performed to study the frequency dependence of the observed g values. We are indebted to J.C.Hensel for these measurements.
A.