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Thermodynamic Interpretation of Pressure-Induced Spin Transitions in Thiosemicarbazonates of Iron(III)

100%
Krupska A.
Acta Physica Polonica A
|
2013
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vol. 124
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issue 4
626-628
EN
The thermodynamic interpretation of the spin transition in iron(II) complexes taking into consideration cooperative domains is given in the literature. We use a similar interpretation for thiosemicarbazonates of aromatic aldehydes of iron(III) compounds. We extend the spin transition interpretation to pressure-induced spin transitions. The relationship between a domain size n and the interaction between a high spin and a low spin states Γp given by Gütlich et al. allows us to deduce a modified equation of the spin transition pressure p_{c} (at the temperature T=T_{c}). On the basis of this equation, the content of the fraction of the high spin state γ and of the fraction of the low-spin state, 1-γ, as a function of pressure can be theoretically estimated. The derived equation enables us to predict the width of hysteresis which refers to the high spin and low spin states formed under the high pressure as a result of the spin transition.
2
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High-Pressure EPR Study of Spin Molecular Bistability in Li[Fe(Th-5Cl-Sa)_2]

100%
Krupska A.
|
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vol. 126
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issue 3
790-795
EN
The spin transitions in Li[Fe(Th-5Cl-Sa)_2] were studied by EPR under hydrostatic pressure in the temperature range 80-332 K. The structural changes in the complex anion induced by the pressure above 350 MPa (when LS-2 phase appears) are observed, which are manifested in abrupt changes in g_{⊥} factor and linewidth ΔB_{⊥} of the low-spin phase LS. It is also manifested in the change in the shape of EPR spectrum. The high-spin ↔ low-spin transition HS ↔ LS shows hysteresis whose width is constant up to about 265 K and then rapidly increases. The spin phase diagram studied shows a large similarity to the phase diagram of (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2], which means that characteristics of the transition depend mainly on complex anion, not on cation. The hysteresis indicates on a cooperative character of the spin transition and on grouping of the complexes in domains.
3
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Influence of Hydrostatic Pressure on the Zero-Field Splitting in NiSnCl_6·6H_2O

64%
Krupska A., Krupski M.
Acta Physica Polonica A
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2003
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vol. 103
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issue 5
453-458
EN
The dependence of the crystal-field splitting parameter D in NiSnCl_6·6H_2O on hydrostatic pressure was determined by the electron paramagnetic resonance method, for the pressures up to 500 MPa. The derivative (∂D/∂p)_T as well as the temperatures and pressures at which the D-parameter reaches zero, were determined. The molecular mechanism responsible for the temperature and pressure changes of the D-parameter is similar to that one observed in the isomorphic NiSiF_6·6H_2O.
4
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Review. High pressure techniques used in the paramagnetic resonances

64%
Krupska A., Krupski M.
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2016
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issue 1
5
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Device for Compressibility and Thermal Expansion Study up to 3 GPa

64%
Krupski M., Krupska A.
Acta Physica Polonica A
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2016
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vol. 130
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issue 6
1324-1325
EN
We present the realization of a project of a device utilizing a standard high-pressure chamber adapted to compressibility and thermal expansion measurements of solids at hydrostatic pressures up to 3 GPa. The device has been tested on the triglycine sulphate crystal (TGS).
6
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Spin Transition Diagram of (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2] Studied by EPR

51%
Krupska A., Augustyniak-Jabłokow M., Yablokov V., Zelentsov V.
Acta Physica Polonica A
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2005
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vol. 108
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issue 2
291-296
EN
The high-spin↔ low-spin transition in (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2] was studied by EPR under hydrostatic pressure in the temperature range of 80-310 K. Two modifications of the low-spin complexes: low-pressure (LS-1) and high-pressure (LS-2) ones were revealed. The low-spin complexes are associated in domains. Under atmospheric pressure LS-1 appears or disappears at 220 K. The hydrostatic pressure shifts the transition to high temperatures. Above 410 MPa the abrupt changes of the g-factor and width Δ B of the EPR line are observed. The pressure-induced transition LS-1 ↔ LS-2 is almost independent of T up to 275 K where under pressure 420 MPa a triple point is observed. When the pressure has been decreased the reverse transition from LS-2 to LS-1 or to high spin phase (at T>260 K) occurs with a large hysteresis about 95 MPa.
7
Content available remote

Electron Paramagnetic Resonance Study of Organic Radicals in Some Herbal Plants

51%
Krupska A., Wojtowicz E., Augustyniak-Jabłokow M.
Acta Physica Polonica A
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2016
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vol. 129
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issue 6
1201-1204
EN
In this work we show the impact of the roasting process on the properties of organic radicals in some herbal products added to cereal coffee. The EPR study shows the presence of radicals in dried herbal products, both natural and roasted. Changes in the relative intensity of the EPR signal and in the g-factor for unroasted and roasted plant material can be observed. This indicates to the recombination processes of radicals. Roasting process increases the number of radicals. The analysis of EPR spectra show that they consist of two Gaussian lines which indicate that there are at least two different kinds of radicals. The values of g-factor about 2 may be derived from a number of very different radicals. For this reason the identification of such radicals is not strictly possible.
8
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EPR Discovery of a New Pressure-Induced Low-Spin Phase in (2Me-5Et-PyH)[Fe(Th-5Cl-Sa)_2]

39%
Krupska A., Augustyniak-Jabłokow M., Yablokov Y., Zelentsov V., Ulanov V., Mroziński J.
|
EN
Electron paramagnetic resonance studies of the high-spin (HS) ↔ low-spin (LS) transition in 2-methyl-5-ethyl-pyridine-5-chloro-salicylalt hiosemicarbazonatoferrate(III) performed under hydrostatic pressure up to 500 MPa in a temperature range of 80-310 K have revealed two modifications of the low spin complexes: low-pressure (LS1) and high-pressure (LS2) ones. Under atmospheric pressure LS1 appears on cooling and disappears on heating at 220 K. The hydrostatic pressure shifts the transition to higher temperatures. Below 275 K an increase in pressure to 410 MPa results in abrupt changes in the g-factor and widthΔ B of the EPR line indicating a transition to a new phase. The pressure-induced transition LS1 ↔ LS2 is almost independent of T up to 275 K, where at a pressure of 420 MPa a triple point is observed. The LS1↔ LS2 and HS↔ LS2 (at T>260 K) transitions occur with a large hysteresis of about 95 MPa. The process of the spin transition has been shown to begin with the formation of domains of LS complexes in the matrix of HS ones. The response of the domains to external factors has been studied.
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