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The Synthesis and Spectroscopic Study of Novel Binuclear Chromium(III) Complex with Pipemidic Acid

Skrzypek D., Kovala-Demertzi D., Szymanska-Niewiadomska B., Kourkoumelis N., Staninska M.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 3

363-371

EN

The interaction of Cr(III) with pipemidic acid, Hpipem, afforded the complex [Cr(pipem)(HO)2(H2O)]2 Cr2O3. The new complex has been characterized by elemental analysis, infrared, XRD and EPR spectroscopy. The EPR spectra of the complex have been recorded down to T = 3 K. The temperature dependence of EPR spectrum demonstrates that spectrum originates from septet transitions at a room temperature and from quintet state for lower temperatures for exchange coupled chromium pairs. The dimer characterizes antiferromagnetic interaction with J = -32 cm-1. The monoanion, pipem, exhibits obligation through the carbonyl and carboxylatooxygen atoms. Six-coordinate dimer distorted octahedral configuration has been proposed for [Cr(pipem)(HO)2(H2O)]2.

2

The Characterization of CuZnZrY Oxide Catalyst in the Steam Reforming of Methanol by EPR and XPS Spectroscopies

Skrzypek D., Krupa K., Talik E., Widuch S.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 2

257-268

EN

In this paper we have developed the characterization of catalyst containing mainly CuO and ZnO with the addition of zirconium and yttrium oxides, using electron paramagnetic resonance (EPR) and X-ray photoelectron (XPS) spectroscopies. The obtained results support the stepwise reduction mechanism of Cu2+ ions. For the catalyst before the steam reforming of methanol reaction (SRM) the copper species were identified as isolated Cu2+ ions. The values of EPR parameters indicate the coordination of four oxygen atoms around Cu(II) in distorted axial configuration. For the catalyst after SRM reaction the EPR spectrum is complex and four types paramagnetic copper species (S1 - S4) could be identified. From theXPS results it is evident that the copper is in a reduced state in the catalyst after reaction. The fitting ofO1s spectrum proves the presence of hydroxide and carbonate anions apart from oxide surface phase. Combining the results of EPR and XPS methods it can be suggested that the S2 - S4 species are present on a surface.

3

The Characterization of Modified Higher Aliphatic Alcohols-Synthesis Catalysts by EPR and XPS Methods

Skrzypek D., Krupa K., Winiarski A., Szymanska B.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 1

145-153

EN

Aseries of copper-zinc catalysts for aliphatic alcohols synthesis with a varying amount of additives was prepared by thermal decomposition of metal citrates. The results of catalytic experiments, made in a laboratory high-pressure reactor, showed a good stability and almost constant activity and selectivity during 4 months. In this paper the catalyst before (A) and after (B) reaction is characterized by EPR and X-ray photoelectron spectroscopies. For catalystAthe copper species were identified as isolated Cu2+ ions in a dynamic Jahn-Teller configuration. For the sample B the EPR spectrum is complex and its features are corresponding to: clustered Cu2+ species with dipole-dipole interaction; Fe3+ ions in rhombically distorted symmetry; O2- centres.

4

Characterisation of amorphous state of REE2Fe2+Be2Si2O10 by spectroscopic methods.

Malczewski D., Skrzypek D., Molak A.

Archives of Materials Science

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2004

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Vol. 25, nr 4

561-571

EN

This paper presents 57Fe Moessbauer spectroscopy, electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), X-ray diffraction (XRD), gamma-ray spectroscopy and dielectric permitivity spectroscopy studies of fully metamict gadolinite REE2Fe2+Be2Si2O10 from Ytterby (Sweden). X-ray and electron diffraction patterns of the sample show complete lack of long range order (LRO). 57Fe Moessbauer spectroscopy of the sample revealed only Fe3+ ions definitely located in octahedral coordinations, similar to thye crystalline structure of gadolinite. The EPR resonance spectrum is complete and its features corespond to Gd3+ and Mn2+ centers. The Gd3+ centers show low-symmetry of local crystal field and may be characterized by distribution of spin-Hamiltonian parameters such as: g-factor and fine-structure parameters. The temperature dependence of utensity proves that a fraction of gadolinium ions interact by superexchange type mechanism and reveals that these exchange interactions are of the antiferromagnetic type Mn2+ centers and the character of Mn2+ EPR spectra indicate that this spectra are atributed to isolated manganium ions. The AC conductivity exhibits thermally activated behavior above 420 K whereas the dielectric constant shows a step-like anomaly near 230 K.