Search results for " Paramagnetic resonance"
showing 10 items of 567 documents
New CpCrCl2(PR3) complexes: physical properties and reduction chemistry
1998
Abstract Compounds CpCrCl2L ( L = PMe 2 Ph , 1 , PMePh 2 , 2 ; PPh 3 , 3 ) have been prepared. Their magnetic moment is in accord with the presence of three unpaired electron and a variable temperature 1H NMR investigation of 1 shows Curie-Weiss behavior. The 1H NMR, EPR and UV-visible spectra are in agreement with those of other previously reported compounds of the same family. An electrochemical investigation shows the accessibility of an irreversible reduction process. A parallel sodium reduction investigation of complexes CpCrCl2L (L = PMe3 and η1-dppe) suggests tjat the reduction process is followed by immediate chloride loss, and then by a ligand redistribution process to afford chrom…
A two-dimensional radical salt based upon BEDT-TTF and the dimeric, magnetic anion [Fe(tdas)2]22−: (BEDT-TTF)2[Fe(tdas)2] (tdas = 1,2,5-thiadiazole-3…
2002
In an attempt to synthesize new synthetic metals which couple magnetic properties to conductivity, we prepared the novel salt (BEDT-TTF)2[Fe(tdas)2] [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, hereafter referred to as ET; tdas = 1,2,5-thiadiazole-3,4-dithiolate] by the electrocrystallization technique. The crystal structure of this compound, as determined by single crystal X-ray diffraction, contains conducting, organic ET layers separated by dimerized, magnetic [Fe(tdas)2]22− anions. Due to the magnetic insulating ground electronic state of the ET layer, thermally activated conductivity is observed, with a room temperature value of about 1 S cm−1. This salt was also characterized by…
Thermodynamic and kinetic control over the oxidation mechanism of the natural vanadyl porphyrin series (DPEP)VO in methylene chloride: electrogenerat…
2006
The electrochemical behavior of the natural (DPEP)VO series (where DPEP is the dianion deoxophylloerythroetioporphyrinate) is studied in methylene chloride. The investigated compounds, which were extracted from oil shales of Tarfaya (Morocco), exhibit a typical electrochemical behavior as compared to that of related synthetic vanadyl porphyrins. The electro-oxidation of (DPEP)VO is characterized by a splitting of the peaks when carried out at a glassy carbon electrode. This can be explained by two possible paths (CE and EC mechanisms) which are characterized by a “square diagram” where the chemical step, C, corresponds to a dimerization (radical–radical or substrate–substrate reaction). The…
Synthesis, Characterization and Magnetic Properties of New Dinuclear Copper(II) Complexes with N,N′-Disubstituted Dithiooxamides derived from α-Amino…
2005
Four new dinuclear copper(II) complexes have been synthesized and have the general formula [Cu2(L)(H2O)2], where L = GLYDTO [N,N′-bis(carboxymethyl)dithiooxamide], ALADTO [N,N′-bis(carboxyethyl)dithiooxamide], VALDTO [N,N′-bis(1-carboxy-2-methylpropyl)dithiooxamide] and LEUDTO [N,N′-bis(1-carboxy-3-methylbutyl)dithiooxamide]. The complexes were characterized by elemental analysis as well as by IR, electronic and EPR spectroscopy. These techniques provided evidence for the presence of the CuNO2S chromophore. Magnetic susceptibility measurements on all the complexes in the range 4–300 K show the existence of a dominant antiferromagnetic interaction with −J values greater than 300 cm−1. Therma…
Metal complexes of sulfanilamide derivatives. Spectroscopic characterization of the dichloro disulfathiazole methanol copper(II) complex
1993
The synthesis and spectral characterization of the [Cu(Hstz)2(MeOH)Cl2] complex are described. Both polycrystalline powder EPR and single crystal EPR spectra recorded at room temperature show rhombic distortion with values of g1=2.25, g2=2.09 and g3=2.03 in agreement with a copper polyhedron, intermediate between trigonal bipyramid and square pyramidal.
Effects of gamma-irradiation on trehalose–hydroxyethylcellulose microspheres loaded with vancomycin
2003
Ionizing radiation can be used as a drug sterilization technique, provided that the drug itself is not modified and that no toxic products are produced; moreover, if the irradiated product is a drug delivery system, the drug release characteristics must not be significantly altered by radiation. The aim of this work was to study the effects of sterilization by ionizing radiation on hydroxyethylcellulose/trehalose spherical micromatrices, containing the antibiotic vancomycin. Our experimental results showed that gamma-rays did not alter the chromophore groups of vancomycin (UV measurements), and did not modify the kinetic behavior of drug release from microspheres. Moreover, no significant c…
A PAS domain with an oxygen labile [4Fe-4S](2+) cluster in the oxygen sensor kinase NreB of Staphylococcus carnosus.
2008
The cytoplasmic histidine sensor kinase NreB of Staphylococcus carnosus responds to O(2) and controls together with the response regulator NreC the expression of genes of nitrate/nitrite respiration. nreBC homologous genes were found in Staphylococcus strains and Bacillus clausii, and a modified form was found in some Lactobacillus strains. NreB contains a sensory domain with similarity to heme B binding PAS domains. Anaerobically prepared NreB of S. carnosus exhibited a (diamagnetic) [4Fe-4S](2+) cluster when assessed by Mossbauer spectroscopy. Upon reaction with air, the cluster was degraded with a half-life of approximately 2.5 min. No significant amounts of Mossbauer or EPR detectable i…
The 4th international comparison on EPR dosimetry with tooth enamel: Part 1: Report on the results
2011
This paper presents the results of the 4th International Comparison of in vitro electron paramagnetic resonance dosimetry with tooth enamel, where the performance parameters of tooth enamel dosimetry methods were compared among sixteen laboratories from all over the world. The participating laboratories were asked to determine a calibration curve with a set of tooth enamel powder samples provided by the organizers. Nine molar teeth extracted following medical indication from German donors and collected between 1997 and 2007 were prepared and irradiated at the Helmholtz Zentrum München. Five out of six samples were irradiated at 0.1, 0.2, 0.5, 1.0 and 1.5 Gy air kerma; and one unirradiated s…
Eu3+ ion distribution in oxyfluoride glass nanocomposites
2019
The authors are grateful to Dr. Andris Fedotovs for photography of the samples. This research is funded by the Latvian Council of Science, project “Novel transparent nanocomposite oxyfluoride materials for optical applications”, project No. LZP-2018/1-0335.
Electron paramagnetic resonance of Gd3 in TlGdSe2
2003
Electron paramagnetic resonance has been studied on the polycrystalline sample of the layer compound TlGdSe 2 . When the temperature is lowered from room temperature the linewidth reaches a shallow minimum near 60 K and then decreases rapidly below 15 K. From the two-dimensional molecular field model two exchange constants J 1 and J 2 with the nearest and next nearest neighbors were estimated. The calculated high-temperature limit of the linewidth (341 mT) is in fair agreement with the experimental value (314 mT). It may be slightly improved after taking into account the preferred orientation of the sample.