Change in the g factors and ESR spectra of chromium(V) complexes on irradiating dichromated gelatin

1985 ◽  
Vol 20 (5) ◽  
pp. 577-581 ◽  
Author(s):  
S. M. Maloletov ◽  
V. P. Sherstyuk
Keyword(s):  
Esr Spectra ◽  
Dichromated Gelatin ◽  
G Factors

TEMPERATURE DEPENDENCES OF Y2Cu2O5 ESR SPECTRA

1989 ◽  
Vol 03 (05) ◽  
pp. 427-435 ◽  
Author(s):  
A.A. GIPPIUS ◽  
V.V. MOSHCHALKOV ◽  
YU. A. KOKSHAROV ◽  
A.N. TIKHONOV ◽  
B.V. MILL ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Single Crystal ◽  
Room Temperature ◽  
Esr Spectra ◽  
Single Line ◽  
Néel Temperature ◽  
Esr Spectrum ◽  
Complicated Form ◽  
Temperature Dependences ◽  
G Factors

Temperature dependences of the ESR spectrum in Y 2 Cu 2 O 5 compound are studied for both polycrystalline and single crystal samples. The g-factors along the main axes are found to be ga=2.099, gb=2.048, and gc=2.21 at room temperature, T=293 K . As temperature decreases, the linewidth ΔH increases in agreement with the Huber’s formula ΔH=A(T N /(T−T N ))β+B(θ/T+1) with the following parameters: A=1513±10 Oe , B=509±10 Oe , T N =7±1 K , θ=18±2 K , β=1.3±0.3. In the vicinity of the Neel Temperature, T N , the ESR spectrum has a very complicated form indicating the existence of clusters with different internal magnetic fields. Below T N , a single line symmetrical ESR spectrum is recovered.

Kinetics of the Thermal Disappearance of Radicals Formed During the Radiolysis of Aspartic Acid

2009 ◽  
Vol 59 (12) ◽  
Author(s):  
Mihai Contineanu ◽  
iulia Contineanu ◽  
Ana Neacsu ◽  
Stefan Perisanu
Keyword(s):  
Thermal Resistance ◽  
Aspartic Acid ◽  
Room Temperature ◽  
Esr Spectra ◽  
Complex Mechanism ◽  
Radical Species ◽  
Mechanisms Of Formation ◽  
Kinetics Of

The radiolysis of the isomers L-, D- and DL- of the aspartic acid, in solid polycrystalline state, was investigated at room temperature. The analysis of their ESR spectra indicated the formation of at least two radicalic entities. The radical, identified as R3, resulting from the deamination of the acid, exhibits the highest concentration and thermal resistance. Possible mechanisms of formation of three radical species are suggested, based also on literature data. The kinetics of the disappearance of radical R3 indicated a complex mechanism. Three possible variants were suggested for this mechanism.

Photolytic and thermal annealing of radical anions gamma-irradiated monocarboxylic acids

1979 ◽  
Vol 44 (12) ◽  
pp. 3632-3643 ◽  
Author(s):  
Karel Mach ◽  
Igor Janovský ◽  
Karel Vacek
Keyword(s):  
Thermal Annealing ◽  
Pivalic Acid ◽  
Esr Spectra ◽  
Paramagnetic Species ◽  
Radical Anions ◽  
Γ Irradiation ◽  
Before And After ◽  
Optical Bleaching ◽  
The Difference ◽  
Gamma Irradiated

Total yields of paramagnetic species, their optical bleaching and thermal annealing in acetic, propionic, a-butyric, isobutyric, and pivalic acid γ-irradiated at 77 K were followed by ESR spectroscopy. Radical anions, always found after irradiation, disappear during optical bleaching without formation of any paramagnetic product. During thermal annealing they are converted almost quantitatively into the α-radicals of the respective acid, with the exception of pivalic acid. Amounts of radical anions were estimated from the difference of integrated ESR spectra taken before and after optical bleaching. The results show that approximately equal amounts of the reduction and oxidation paramagnetic products of the γ-irradiation can be detected.

Electrochemical behaviour and ESR spectra of nitro substituted mono- and dibenzoylmethylenebenzthiazolines and selenazolines

1979 ◽  
Vol 44 (5) ◽  
pp. 1540-1551 ◽  
Author(s):  
Jaro Komenda ◽  
Jiří Huzlík
Keyword(s):  
Electron Transfer ◽  
Esr Spectroscopy ◽  
Electrochemical Behaviour ◽  
Spectroscopic Studies ◽  
Esr Spectra ◽  
Slow Electron

Compounds of the type of 2-(4'-nitrobenzoyl)methylene-3-ethylbenzothiazoline (I) and 2-bis-(p-nitrobenzoyl)methylene-3-ethylbenzothiazoline (II) were studied polarographically and by ESR spectroscopy to obtain informations about their electrochemical and follow-up reactions and their conformation. Whereas with compounds of the type I the conjugation in their molecules is preserved, with type II the coplanarity of the molecules is disturbed, which is manifested in the values of the splitting constants of the ESR spectra and a slow electron transfer between both nitrophenyl substituents. These conclusions are supported by NMR spectroscopic studies.

Intermolecular hydrogen transfer in unsaturated hydrocarbons induced by dimeric titanocene

1983 ◽  
Vol 48 (10) ◽  
pp. 2924-2936 ◽  
Author(s):  
Karel Mach ◽  
Lidmila Petrusová ◽  
Helena Antropiusová ◽  
Vladimír Hanuš ◽  
František Tureček ◽  
...  
Keyword(s):  
Hydrogen Transfer ◽  
Titanium Content ◽  
Esr Spectra ◽  
Stable Complex ◽  
Catalytic Complex ◽  
Substitution Reactions ◽  
Unsaturated Hydrocarbons ◽  
Linear Alkanes ◽  
Saturated And Aromatic Hydrocarbons ◽  
Intermolecular Hydrogen Transfer

μ-(η5 : η5-Fulvalene)-di-μ-hydrido-bis(η5-cyclopentadienyltitanium) and μ-(η5 : η5-fulvalene)-μ-chloro-μ-hydrido-bis(cyclopentadienyltitanium) form a thermally stable complex which catalyzes the intermolecular hydrogen transfer in unsaturated hydrocarbons, in addition to isomerizations and cyclizations. Cyclic hydrocarbons disproportionate under catalysis to saturated and aromatic hydrocarbons, while linear olefins yield predominantly linear alkanes and high molecular weight tar. The catalyst enables the hydrocarbon system to approach the thermodynamic equilibrium through a series of substitution reactions between alkyl- and allyltitanocene-like species and olefins and dienes. The catalytic complex was characterized by UV and ESR spectra. About one half of overall titanium content could be converted to mononuclear η3-allyltitanocene-like species, stable up to 400 °C. This exceptional thermal stability is ascribed to a firmly bound allyl containing ligand.

ESR study of the structure and bonding situation in thiocyanatocopper(II) complexes with imidazole derivatives

1988 ◽  
Vol 53 (1) ◽  
pp. 56-60
Author(s):  
Anna Mašlejová ◽  
Reinhard Kirmse
Keyword(s):  
Unpaired Electron ◽  
Hyperfine Splitting ◽  
Esr Spectra ◽  
Ligand Field ◽  
Imidazole Derivatives ◽  
Bonding Parameters ◽  
Monomeric Complex ◽  
Structure And Bonding ◽  
Frozen Solutions ◽  
Planar Symmetry

ESR spectra of thianatocopper(II) complexes with imidazole derivatives were studied in ethanolic solutions at 295 and 123 K. Axialsymmetric spectra, attributed to the monomeric complex units, were obtained for the frozen solutions. The bonding parameters were interpreted by using calculated g, Cu-hyperfine, and 14N-ligand hyperfine splitting values. The Cu-N bond parameters indicate a considerable delocalization of the unpaired electron. The values of the isotropic Cu-hyperfine splitting suggest that the deviations from the planar symmetry of the CuN4 units are due to tetrahedral perturbation of the ligand field.

Association of radical anion with alkali cations. IV. ESR study of the 4-nitrobenzophenone radical anion

1980 ◽  
Vol 45 (2) ◽  
pp. 369-375 ◽  
Author(s):  
Stanislav Miertuš ◽  
Ondrej Kyseľ
Keyword(s):  
Hyperfine Splitting ◽  
Radical Anion ◽  
Esr Spectroscopy ◽  
Supporting Electrolyte ◽  
Esr Spectra ◽  
Proton Donor ◽  
Alkali Cations

The 4-nitrobenzophenone radical anion prepared by electrolysis was studied by ESR spectroscopy. On the basis of the interpretation of ESR spectra, the conformation of this system was estimated. The effect of the concentration of supporting electrolyte and of the presence of a proton-donor agent (C2H5OH) was examined. It is assumed that changes in hyperfine splitting constants are caused by association.

An ESR study of the peroxidase reaction catalyzed by human methaemoglobin and methaemoglobin-haptoglobin complex

1991 ◽  
Vol 56 (4) ◽  
pp. 923-932
Author(s):  
Jana Stejskalová ◽  
Pavel Stopka ◽  
Zdeněk Pavlíček
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Amino Acid ◽  
Peroxidase Activity ◽  
Amino Acid Analysis ◽  
Superoxide Radical ◽  
Esr Spectra ◽  
The Other ◽  
Delocalized Electron

The ESR spectra of peroxidase systems of methaemoglobin-ascorbic acid-hydrogen peroxide and methaemoglobin-haptoglobin complex-ascorbic acid-hydrogen peroxide have been measured in the acetate buffer of pH 4.5. For the system with methaemoglobin an asymmetrical signal with g ~ 2 has been observed which is interpreted as the perpendicular region of anisotropic spectrum of superoxide radical. On the other hand, for the system with methaemoglobin-haptoglobin complex the observed signal with g ~ 2 is symmetrical and is interpreted as a signal of delocalized electron. After realization of three repeatedly induced peroxidase processes the ESR signal of the perpendicular part of anisotropic spectrum of superoxide radical is distinctly diminished, whereas the signal of delocalized electron remains practically unchanged. An amino acid analysis of methaemoglobin along with results of the ESR measurements make it possible to derive a hypothesis about the role of haptoglobin in increasing of the peroxidase activity of methaemoglobin.

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