Synthesis And Spectroscopic Studies Of New Bis(N-1-hydroxy-2,6-Di-Fe/Tf-Butylphenyl- Salicylideneaminato)Cobalt(Ii) Complexes And Their Oxidation With PbO2

2001 ◽  
Vol 56 (8) ◽  
pp. 778-786 ◽  
Author(s):  
Veli T. Kasumov ◽  
Bünyamin Karabulut ◽  
Ibrahim Kartal ◽  
Fevzi Köksal
Keyword(s):  
Aromatic Ring ◽  
Hyperfine Coupling ◽  
Spectroscopic Properties ◽  
Spectroscopic Studies ◽  
Esr Spectra ◽  
Coupling Constants ◽  
Paramagnetic Species ◽  
Phenoxyl Radicals ◽  
Stable Phenoxyl ◽  
D Orbitals

A series of new bis[N-(1-OH-2,6-di-tert-butylphenyl)salicylaldiminato]cobalt(II) complexes possessing one or two HO- and CH3O - substituents on the salicylaldehyde moiety were prepared, and their spectroscopic properties as well as their oxidation with PbO2 were examined. ESR data indicate that oxidation of the complexes produces stable phenoxyl radicals. All phenoxyl radicals have similar g-values and hyperfine coupling constants, which are influenced very little by the substituents and by coordination. The experimental observations indicate that the Co(L·x)2 radicals are ligand-localized and that there is no notable contribution from the metal d-orbitals to the values of the g-factors. Satellite peaks from the 13C nuclei in the aromatic ring were also observed. The ESR spectra of some of the complexes showed partial conversion of primary radicals to secondary paramagnetic species exhibiting interaction with 59Co(I = 7/2) and 14N nuclei

Nitroxide derivatives of acetylacetone as spin-labelled ligands

1981 ◽  
Vol 59 (1) ◽  
pp. 156-163 ◽  
Author(s):  
D. Plancherel ◽  
D. R. Eaton
Keyword(s):  
Electron Spin Resonance ◽  
Metal Complex ◽  
Electron Spin ◽  
Hyperfine Coupling ◽  
Esr Spectra ◽  
Enol Form ◽  
Coupling Constants ◽  
Spin Resonance ◽  
Steric Factors ◽  
Derivatives Of

Electron spin resonance spectra are reported from a number of radicals derived from 2,4-pentadione substituted at the 3 position with nitroxide-containing groups. If the substituent is t-butyl nitroxide no metal complexes are formed. This is attributed to steric factors which prevent the formation of the enol form of the β-diketone. If the substituent is trifluoromethyl nitroxide two types of metal complex have been observed. The esr spectra of the first type are very similar to that of the uncomplexed radical. Such complexes are formed with Co(III) and Al(III). The esr spectra of the second type show considerably increased 14N and 19F hyperfine coupling constants and in some cases large couplings to the metal nucleus. Complexes for the second type have been observed with Pd(II), Pt(II), and Rh(III). The possible structures of these radicals are discussed.

Substituent effects on benzylic radical hydrogen hyperfine coupling constants. Part 4. The effect of branching of the alkyl substituent

1985 ◽  
Vol 63 (9) ◽  
pp. 2378-2383 ◽  
Author(s):  
Danial D. M. Wayner ◽  
Donald R. Arnold
Keyword(s):  
Hyperfine Coupling ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Esr Spectra ◽  
Coupling Constants ◽  
Molecular Orbital Calculations ◽  
Methyl Ethyl ◽  
Hyperfine Coupling Constants ◽  
Benzyl Radical ◽  
Spin Resonance

The effects of substituents in the meta and para positions of the benzyl radical on the α-hydrogen hyperfine coupling constants (hfc's) are discussed. The electron spin resonance (esr) spectra of the para-methyl, ethyl, isopropyl, and tert-butyl substituted benzyl and cumyl radicals are analysed. Hyperconjugation involving the C—C bond is 40–60% as effective as C—H hyperconjugation for delocalizing spin density. This conclusion is supported by INDO molecular orbital calculations. Similar analysis of the 13Cmr spectra of the para-alkyl substituted cumyl carbocations provides evidence that C—C hyperconjugation is 75–90% as effective as C—H hyperconjugation for delocalizing charge density.

scholarly journals ESR, Structure and Reactions of Specifically Deuterated C6— C8 n-alkane Cations in Halogenated Matrices

1985 ◽  
Vol 40 (1) ◽  
pp. 52-65
Author(s):  
G. Dolivo ◽  
A. Lund
Keyword(s):  
Glass Transition ◽  
Hyperfine Coupling ◽  
Esr Spectra ◽  
Molecular Ions ◽  
Coupling Constants ◽  
Melting Points ◽  
Mo Calculations ◽  
Molecular Cations ◽  
Experimental Values ◽  
Frozen Solutions

Dilute frozen solutions (1-2%) of specifically labelled n-hexane, n-heptane and n-octane in three halogenated matrices (CFCl3, CF3CCl3 and CF2ClCFCl2) have been X-irradiated at 77 K in order to produce the molecular cations. ESR spectra were recorded to temperatures up to the glass transition or melting points of the matrices. Several conformers differing in the geometric structure were observed. The 120° gauche conformers of the n-alkane molecular ions are stabilized by end D-labelling. Revised assignments of their coupling constants were obtained. The extended geometry was predominant in CFCl3 with one exception. INDO MO calculations show that tilting of the CH3 group towards the -CH2- chain lowers the energy and gives better agreement with experimental values for the hyperfine coupling constants. CF3CCl3 seemed to induce the largest distortions in the geometry of the ions. The nature of a distorted conformer of hexane+ in CF3CCl3 has been determined with the aid of observed couplings and INDO MO calculations.Photobleaching causes disappearance of the cations in the CFCl3 and CF2ClCFCl2 matrices and fragmentation to produce 2-butene cations in CF3CCl3. This product was not identified when labelled compounds were employed. The mechanism is discussed.

The electron spin resonance spectra of dioxene radical cations

1989 ◽  
Vol 67 (11) ◽  
pp. 1748-1752 ◽  
Author(s):  
Alwyn G. Davies ◽  
Charles J. Shields ◽  
Jeffrey C. Evans ◽  
Christopher C. Rowlands
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Hyperfine Coupling ◽  
Radical Cations ◽  
Esr Spectra ◽  
Coupling Constants ◽  
Ring Inversion ◽  
Endor Spectroscopy ◽  
Spin Resonance ◽  
Methylene Groups

The electron spin resonance spectra of the radical cations of dioxene (1a), 2,3-dimethyldioxene (1b), 2,3-diphenyldioxene (1c), and benzodioxane (2) in fluid solution have been observed and analysed, with the help of ENDOR spectroscopy in the case of 1c. It is concluded that in 1c the molecule has overall C2 molecular symmetry. In all four compounds, the pseudo-axial and pseudo-equatorial protons of the methylene groups in the half-chair dioxene rings are distinguished by different hyperfine coupling constants, and simulation of the spectra over a range of temperatures has given the Arrhenius parameters for the ring inversion of 1a, 1b, and 2. Keywords: ESR spectra, radical cation, 1,4-dioxene, inversion barrier.

scholarly journals Isotropic Spin Trap EPR Spectra Simulation by Fast Fourier Transform (FFT)

2005 ◽  
Vol 2 (2) ◽  
pp. 165-170
Author(s):  
S. Laachir ◽  
M. Moussetad ◽  
R. Adhiri ◽  
A. Fahli
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Hyperfine Coupling ◽  
Spin Trap ◽  
Esr Spectra ◽  
Coupling Constants ◽  
Spectral Parameters ◽  
Simulation Based ◽  
Spin Resonance ◽  
Isotropic Spin

The detection and investigation of free radicals forming in living systems became possible due to the introduction of the method of spin traps. In this work, the electron spin resonance (ESR) spectra of DMPO/HO. and MGD-Fe-NO adducts are reproduced by simulation, based on the Fast Fourier Transform (FFT). The calculated spectral parameters as the hyperfine coupling constants, agree reasonably with the experimental data and the results are discussed.

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