A single-crystal proton ENDOR study of the ClO<sub>3</sub>centre in γ-irradiated barium perchlorate at 120 K

Atherton, N. M.; Blackford, R. D. S.

doi:10.1039/f29878300569

Cited by 3 publications

(3 citation statements)

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“…In solution, the anion-radical of anthraquinone or its protonated forms do not have an isotropic proton hyperfine coupling larger than 3.5−4.5 MHz . This agrees with HYSCORE spectra of these radicals in frozen solutions, where we do not observe proton splittings larger than 3−5 MHz.…”

Section: Discussionsupporting

confidence: 88%

Pulsed EPR Study of Orthophosphoric and Boric Acid Modified γ-Alumina

et al. 1996

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CW EPR, pulsed ENDOR, and one- and two-dimensional ESEEM techniques have been applied to study the influence of H3PO4 and H3BO3 acid modification of γ-Al2O3 on the strong electron acceptor sites of γ-Al2O3 using adsorbed anthraquinone and o-chloranil as probe molecules. After the adsorbtion, electron transfer produces free radicals at active sites on the activated γ-Al2O3. The observed spectra are the superposition of spectra from radicals simply adsorbed on the surface and from three different paramagnetic complexes of anthraquinone with coordinatively unsaturated aluminum. The isotropic hyperfine coupling of aluminum nuclei in these complexes is ∼2.5, 21, and 28 MHz. Treatment of γ-Al2O3 with H3PO4 decreases the relative amounts of adsorbed radical and the complex with 2.5 MHz hyperfine coupling. The H3BO3 treatment, in contrast, gives only the complex with the 21 MHz hyperfine coupling, and its resolved EPR spectrum indicates two equivalent aluminums in this active site. The ESEEM spectra show only weak dipole−dipole interaction with 31P and 11B nuclei located around the paramagnetic complex. These results suggest that acid modification alters the catalytic properties by changing the number and type of catalytic sites on the surface without introducing new species.

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Section: Discussionsupporting

confidence: 88%

Pulsed EPR Study of Orthophosphoric and Boric Acid Modified γ-Alumina

et al. 1996

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“…Examples of ENDOR measurements for small inorganic radicals formed by ionizing radiation of inorganic crystals have been reported [121][122][123][124][125][126][127][128][129]. For example, K 2 SO 4 single crystals doped with CrO 4 2ions could be characterized by the location of the nearby protons [122].…”

Section: Polymeric Systemsmentioning

confidence: 99%

“…For example, K 2 SO 4 single crystals doped with CrO 4 2ions could be characterized by the location of the nearby protons [122]. In a -irradiated BaClO 4 :3H 2 O single crystal at 120 K, the hyperfine coupling tensors for 24 protons were detected with small isotropic components and their dipolar components were found to be close to axial [124]. In -irradiated CsH 2 AsO 4 and CsD 2 AsO 4 ferroelectric crystals, 133 Cs and 1 H superhyperfine couplings for the AsO 4 center were studied [125].…”

Section: Polymeric Systemsmentioning

confidence: 99%

Endor Spectroscopy

Kispert

Piekara-Sady

Handbook of Applied Solid State Spectroscopy

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To understand what electron nuclear double resonance (ENDOR) transitions are, let us consider the energy levels of a system containing one unpaired electron (S = ½) and one nuclear spin (I = ½), as in a hydrogen atom. Since the electron spin and nuclear spin can each be oriented with or against the external magnetic field, there are four possible energy levels as shown in Figure 4.1. The two electron spin eigenfunctions are denoted by e and e , whereas the two nuclear spin wavefunctions are denoted n and n . In the presence of a large external applied field, the selection rule in electron paramagnetic resonance (EPR) is that the electron flips (changes directions) but the nuclear spin does not flip in an EPR transition. Thus, in Figure 4.1, an EPR transition will occur between energy levels 1 and 4 and a second EPR transitions will occur between energy levels 2 and 3. The intensity of the transition between energy levels 1 and 4 will depend on the population differences of these two energy levels. If one then applies a nuclear frequency to the system, which corresponds to either the energy difference between levels 4 and 3 or the difference between lines 2 and 1, one will induce nuclear spin flip that will change the populations in energy levels 4 and 1, respectively. This changes the intensity of the observed EPR signal. This change in intensity is referred to as the ENDOR response. Figure 4.1 Energy diagram for S = 1/2 and I = 1/2.

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The Hydration of Vanadyl Doped into Magnesium Acetate: Single Crystal Proton ENDOR at 20 K

Atherton

Oliva

1989

Israel Journal of Chemistry

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The single crystal ESR and proton ENDOR of VO2+ doped into magnesium acetate tetrahydrate have been studied at 20 K. The VO2+ ion occupies Mg2+ sites, replacing Mg2+ together with one water molecule. Hyperfine tensors for the six protons in the three coordinating water molecules have been determined and their dipolar components used to construct a model of the proton geometry. The relation of the structure to that of {VO(H2O)5}2+ in a Tutton salt and in frozen aqueous solutions of vanadyl sulphate is discussed.

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A single-crystal proton ENDOR study of the ClO₃centre in γ-irradiated barium perchlorate at 120 K

Cited by 3 publications

References 1 publication

Pulsed EPR Study of Orthophosphoric and Boric Acid Modified γ-Alumina

Pulsed EPR Study of Orthophosphoric and Boric Acid Modified γ-Alumina

Endor Spectroscopy

The Hydration of Vanadyl Doped into Magnesium Acetate: Single Crystal Proton ENDOR at 20 K

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A single-crystal proton ENDOR study of the ClO3centre in γ-irradiated barium perchlorate at 120 K

Cited by 3 publications

References 1 publication

Pulsed EPR Study of Orthophosphoric and Boric Acid Modified γ-Alumina

Pulsed EPR Study of Orthophosphoric and Boric Acid Modified γ-Alumina

Endor Spectroscopy

The Hydration of Vanadyl Doped into Magnesium Acetate: Single Crystal Proton ENDOR at 20 K

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A single-crystal proton ENDOR study of the ClO₃centre in γ-irradiated barium perchlorate at 120 K