Konformationsuntersuchungen durch Elektronenspinresonanz Two-Jump-prozesse in Benzyl-phosphonium Salzen / Conformation Studies by Electron Spin Resonance Two-Jump Process in Benzyl-phosphonium Salts

1976 ◽  
Vol 31 (12) ◽  
pp. 1620-1629
Author(s):  
Klaus Scheffler ◽  
Klaus Hieke ◽  
Paul Schüler ◽  
Hartmut B. Stegmann
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Jump Process ◽  
Esr Spectra ◽  
Coupling Constants ◽  
Phosphonium Salts ◽  
Hindered Rotation ◽  
Limit Value ◽  
Spin Resonance ◽  
Phosphorus Nucleus

AbstractThe ESR spectra of 4-oxyl-benzyl-phosphonium-bromide radicals show a temperature dependence of the methylene protons and the phosphorus nucleus coupling constants which is explained by a hindered rotation of the phenoxyl ring of the radicals. Furthermore compounds with different phosphor substituents exhibit the phenomenon of a two jump process. This effect is described by an isomerisation of two symmetric radical conformations. Activation energies for this process are found to be around 7 kcal/Mol. The conformation of the radicals can be discussed as staggered ethane analogues. A lower limit value for the hyperconjugation Bᴾ -parameter is proposed.

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.

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.

FREE RADICALS OF BIOLOGICAL INTEREST: PART II. ELECTRON SPIN RESONANCE (ESR) SPECTRA OF 2537 A IRRADIATED AMINO ACIDS

1967 ◽  
Vol 45 (12) ◽  
pp. 1831-1839 ◽  
Author(s):  
W. F. Forbes ◽  
P. D. Sullivan
Keyword(s):  
Amino Acids ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Hydrogen Abstraction ◽  
Esr Spectra ◽  
Side Chain ◽  
Biological Interest ◽  
Spin Resonance ◽  
Cyclohexadienyl Radical ◽  
Secondary Radical

Polycrystalline amino acids, when irradiated with 2537 Å light, afford a variety of electron spin resonance signals. These signals are generally stable at room temperature for relatively long periods of time. For a number of the spectra obtained, there is evidence that more than one radical species contributes to the observed spectra. The signals obtained frequently differ from those obtained on exposure to ionizing radiation. The postulated species formed can often be visualized as being formed by effective hydrogen abstraction from the alkyl-substituted tertiary carbon atom or from the —OH, —SH or —NH group contained in the side chain. For L-phenylalanine a secondary radical is obtained, which is ascribed to a cyclohexadienyl radical.

Electron spin resonance observations of photochemically generated contact ammonium ion-pairs of fluoro-substituted ketones

1979 ◽  
Vol 57 (5) ◽  
pp. 600-602 ◽  
Author(s):  
K. S. Chen ◽  
T. Foster ◽  
J. K. S. Wan
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Ion Pairs ◽  
Esr Spectra ◽  
Ammonium Ion ◽  
Spin Resonance ◽  
Photochemical Systems

Contact radical ion-pairs of ammonium and fluoro-substituted ketones were generated in photochemical systems and their here-to-fore elusive esr spectra were characterized.

Electron Spin Resonance Investigations on Perovskite Solar Cell Materials Deposited on Glass Substrate

MRS Advances ◽  
2018 ◽  
Vol 3 (32) ◽  
pp. 1831-1836
Author(s):  
C. L. Saiz ◽  
E. Castro ◽  
L. M. Martinez ◽  
S. R. J. Hennadige ◽  
L. Echegoyen ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Solar Cell ◽  
Line Width ◽  
Electron Spin ◽  
Glass Substrate ◽  
Esr Spectra ◽  
Perovskite Solar Cell ◽  
Hole Transport ◽  
Ex Situ ◽  
Spin Resonance

ABSRTACTIn this article, we report low-temperature electron spin resonance (ESR) investigations carried out on solution processed three-layer inverted solar cell structures: PC61BM/CH3NH3PbI3/PEDOT:PSS/Glass, where PC61BM and PEDOT:PSS act as electron and hole transport layers, respectively. ESR measurements were conducted on ex-situ light (1 Sun) illuminated samples. We find two distinct ESR spectra. First ESR spectra resembles a typical powder pattern, associated with gx = gy = 4.2; gz = 9.2, found to be originated from Fe3+ extrinsic impurity located in the glass substrate. Second ESR spectra contains a broad (peak-to-peak line width ∼ 10 G) and intense ESR signal appearing at g = 2.008; and a weak, partly overlapped, but much narrower (peak-to-peak line width ∼ 4 G) ESR signal at g = 2.0022. Both sets of ESR spectra degrade in intensity upon light illumination. The latter two signals were found to stem from light-induced silicon dangling bonds and oxygen vacancies, respectively. Our controlled measurements confirm that these centers were generated during UV-ozone treatment of the glass substrate –a necessary step to be performed before PEDOT:PSS is spin coated. This work forms a significant step in understanding the light-induced- as well as extrinsic defects in perovskite solar cell materials.

Microscopic Study of Metal Hydrides using Electron Spin resonance

1980 ◽  
Vol 3 ◽  
Author(s):  
E. L. Venturini
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Metal Hydrides ◽  
Esr Spectra ◽  
Spectroscopic Technique ◽  
Host Lattice ◽  
Hydrogen Ions ◽  
Spin Resonance ◽  
Symmetry Phase ◽  
Paramagnetic Ions

ABSTRACTElectron spin resonance (ESR) of dilute paramagnetic ions in nonmagnetic metallic hydrides provides microscopic information about the hydrogen ions in the immediate vicinity of the impurity. By comparing ESR spectra for different host metals and several hydrogen/metal ratios, one can determine material properties including host lattice symmetry, phase boundaries and occupation of available sites by hydrogen. Examples are presented of ESR of dilute Er in group IIIB and IVB metal hydrides, demonstrating the sensitivity and versatility of ESR as a spectroscopic technique.

A comparison of electron spin resonance α- and β-hyperfine coupling constants in para-substituted α-phenethyl radicals

1986 ◽  
Vol 64 (4) ◽  
pp. 769-772 ◽  
Author(s):  
Donald R. Arnold ◽  
A. Martin de P. Nicholas ◽  
Kent M. Young
Keyword(s):  
Electron Spin Resonance ◽  
Experimental Evidence ◽  
Linear Relationship ◽  
Electron Spin ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Hyperfine Coupling Constants ◽  
Spin Resonance ◽  
Benzyl Radicals ◽  
Spin Delocalization

The linear relationship between the electron spin resonance hyperfine coupling constants (hfc) of the α- and β-hydrogens of para-substituted α-phenethyl radicals provides experimental evidence that the magnitude of both the α- and β -hfc is determined largely by the extent of spin delocalization in these benzylic systems. The [Formula: see text] scale, developed using substituted benzyl radicals, is shown to apply to phenethyl radicals as well.

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