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.

Electron Spin Resonance Super-Hyperfine Splitting Study of Polycrystalline Niobocene and Vanadocene Dichlorides

1996 ◽  
Vol 61 (12) ◽  
pp. 1767-1772 ◽  
Author(s):  
Jana Holubová ◽  
Zdeněk Černošek ◽  
Ivan Pavlík
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Unpaired Electron ◽  
Hyperfine Splitting ◽  
Hyperfine Coupling Constant ◽  
Esr Spectra ◽  
Coupling Constant ◽  
Average Value ◽  
Spin Resonance ◽  
Vanadocene Dichloride

The electron spin resonance (ESR) spectra of niobocene and vanadocene dichlorides were studied on the title compounds prepared as magnetically diluted species in polycrystalline form. The resolved super-hyperfine splitting of anisotropic ESR spectra of both studied compounds was firstly observed. Computer simulation confirmed that this super-hyperfine splitting is due to interaction of unpaired electron with nuclear spin of two chlorine ligands. Average value of super-hyperfine coupling constant is 13.3 MHz for niobocene dichloride. For vanadocene dichloride, it is estimated to be in the range of 6-10 MHz. It corresponds approximately to 10% delocalization of metal unpaired electron spin density onto chlorine ligands in case of niobocene dichloride and to 4-7% delocalization in case of vanadocene dichloride.

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.

Niobocene Dichloride and Niobocene Diiodide: Electronic Absorption Spectra and Electron Spin Resonance

1998 ◽  
Vol 63 (5) ◽  
pp. 628-635 ◽  
Author(s):  
Jana Holubová ◽  
Zdeněk Černošek ◽  
Ivan Pavlík
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Point Group ◽  
Esr Spectra ◽  
Ligand Field ◽  
Orbital Interaction ◽  
Symmetry Point Group ◽  
Spin Orbital ◽  
Halide Ligands

The effect of the halide ligand on the bonding of niobium in niobocene dichloride and niobocene diiodide was investigated. The electronic absorption spectra of the two compounds in the range of d-d transitions were resolved into four bands corresponding to transitions of the d1 electron between five frontier orbitals in a molecule of symmetry point group C2v. The energies of the frontier molecular orbitals were determined relatively to the energy of the orbitals in the spherically symmetric ligand field formed by the appropriate halide ligands. The effect of the halide ligands on the spin-orbital interaction of the HOMO orbital is discussed qualitatively on the basis the ESR spectra.

Spin Label Study of Apomembranes and Purple Membranes

1993 ◽  
Vol 48 (5-6) ◽  
pp. 500-503
Author(s):  
Tzvetana R. Lazarova ◽  
Maya Y. Velitchkova
Keyword(s):  
Fatty Acids ◽  
Lipid Bilayer ◽  
Spin Label ◽  
Hyperfine Splitting ◽  
Esr Spectra ◽  
Spin Labels ◽  
Label Study ◽  
Splitting Parameter ◽  
Induced Changes ◽  
Purple Membranes

Abstract Three spin-labelled fatty acids were used to detect the dynamics of lipid bilayer of apomem branes and purple membranes. It was found that ESR spectra of spin labels bound to apo­ membranes showed a temperature-induced changes rather similar to those seen with purple membranes. At the same time, however, the values of hyperfine splitting parameter 2Tm were lower as compared to purple membranes. The results pointed out that the removal of the retinal from purple membranes affects the dynamics of lipid bilayer and apomembranes were more rigid structure than those of purple membranes.

An ESR and calorimetric study of iron oolitic samples from the Northampton ironstone

Clay Minerals ◽  
1990 ◽  
Vol 25 (3) ◽  
pp. 303-311 ◽  
Author(s):  
A. U. Gehring ◽  
R. Karthein
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Hyperfine Splitting ◽  
Esr Spectroscopy ◽  
Thermal Conversion ◽  
Esr Spectra ◽  
Calorimetric Study ◽  
Calorimetric Methods ◽  
Mineral Phases ◽  
Spin Resonance

AbstractElectron spin resonance (ESR) spectroscopy and calorimetric methods were used to characterize conversion processes in multimineral samples from the Northampton ironstone (NIS) at temperatures between 25°C and 800°C. The beginning of the thermal conversion processes can be determined by the formation of asymmetric ESR spectra with g ≈ 2 at 250°C. The breakdown of the berthierine structure between 250°C and 520°C is indicated by the disappearance of the hyperfine splitting in the Mn2+ spectrum and the formation of magnetite. The decomposition of siderite and calcite was found by calorimetric methods at 580°C and 700°C, respectively. The hematite formation between 550°C and 800°C is explained by the decomposition of siderite but also by the oxidation of previously formed magnetite. The occurrence of hematite as the dominant ferric oxide at 800°C signifies the end of the conversion process of the major mineral phases in the NIS samples.

Die reversible Einelektronen-Oxydation von Metallochlorinen und ein Vergleich der Liganden Octaäthylporphin und -chlorin

1970 ◽  
Vol 25 (3) ◽  
pp. 255-265 ◽  
Author(s):  
Jürgen-Hinrich Fuhrhop
Keyword(s):  
Saturated Calomel Electrode ◽  
Esr Spectra ◽  
Ligand Field ◽  
Ionic Character ◽  
Unusual Behavior ◽  
Oxidation Potentials ◽  
Porphyrin Derivatives ◽  
The One ◽  
Porphyrin Macrocycles ◽  
Metal Ligand

Many metallochlorins can be reversibly oxidized in a one electron step. The midpoint oxidation potentials of magnesium-octaethyl-chlorin (MgOÄC), ZnOÄC, CuOÄC, NiOÁC and PdOÄC were found to be approximately 107, 197, 331, 356, and 422 mV vs. a saturated calomel electrode in chloroformmethanol. As with analogous metalloporphyrins the order of the oxidations potentials increases approximately linearly with the electronegativity values of the metal ions. The midpoint potentials of the one-electron oxidation of metallochlorins were found to be about 300 mV lower than those of analogous metallporphyrins. Sn (IV) -OÄC-dihydroxide and the monocation of OÄC could not be reversibly oxidized. A simple electrostatic argument can explain the oxidation behavior of these and other porphyrin derivatives. The more negative the ligand ring, the easier it is to remove an electron and vice versa. Thus experimental results point to a more ionic character of the metal-ligand bonds in metallochlorins as compared to metalloporphyrins. The unusual behavior of chlorophyll a and the optical and ESR-spectra of the resulting radicals are discussed.Some general properties of the chlorin- and porphyrin macrocycles are compared. Characteristic differences between the two ligand-systems are explained by the low basicity of the pyrrolin-nitrogen and the decreased symmetry of the ligand field in the chlorins.

Oxygen−17 Hyperfine Splitting Constants in the ESR Spectra of p‐Semiquinones—17O

1967 ◽  
Vol 46 (12) ◽  
pp. 4891-4902 ◽  
Author(s):  
M. Broze ◽  
Z. Luz ◽  
B. L. Silver
Keyword(s):  
Hyperfine Splitting ◽  
Esr Spectra
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