Category Archives: EPR

Dynamic Nuclear Polarization with Polychlorotriphenylmethyl Radicals: Supramolecular Polarization-Transfer Effects

C. Gaellieri et al., Dynamic Nuclear Polarization with Polychlorotriphenylmethyl Radicals: Supramolecular Polarization-Transfer Effects, Angew. Chem. Int. Ed., 2010, 49, 3360-3362

http://dx.doi.org/10.1002/anie.201000031

Polychlorinated trityl radicals (see structure: C black, Cl green, Na gray, O red) used for dynamic nuclear polarization (DNP) showed a new transfer mechanism involving quadrupolar chlorine nuclei. The observation of positive or negative enhancements, depending on the substrate, highlights the supramolecular character of the initial polarization-transfer process.

Dynamic Nuclear Polarization with Polychlorotriphenylmethyl Radicals: Supramolecular Polarization-Transfer Effects

C. Gaellieri et al., Dynamic Nuclear Polarization with Polychlorotriphenylmethyl Radicals: Supramolecular Polarization-Transfer Effects, Angew. Chem. Int. Ed., 2010, 49, 3360-3362

http://dx.doi.org/10.1002/anie.201000031

Polychlorinated trityl radicals (see structure: C black, Cl green, Na gray, O red) used for dynamic nuclear polarization (DNP) showed a new transfer mechanism involving quadrupolar chlorine nuclei. The observation of positive or negative enhancements, depending on the substrate, highlights the supramolecular character of the initial polarization-transfer process.

EUROMAR 2011 in Frankfurt/Germany

Please mark your calendars, the EUROMAR 2011 will be held this year in Frankfurt/Germany from August 21st to 25th. The conference will be held in conjunction with the 33rd Discussion Meeting of the Magnetic Resonance Spectroscopy Division of the Gesellschaft Deutscher Chemiker (GDCh). Furthermore, the EUROMAR will be accompanied for the first time by the 8th European Federation of EPR Groups Meeting, a triennial meeting of all European EPR Groups and the Meeting of the International EPR Society.

The conference will cover all aspects of magnetic resonance spectroscopy such as methodological and technical advancements as well as new areas of application in material and life sciences, physics, chemistry and biology. Registration and abstract submission are open now. For further details please visit www.euromar2011.org.

EUROMAR 2011 in Frankfurt/Germany

Please mark your calendars, the EUROMAR 2011 will be held this year in Frankfurt/Germany from August 21st to 25th. The conference will be held in conjunction with the 33rd Discussion Meeting of the Magnetic Resonance Spectroscopy Division of the Gesellschaft Deutscher Chemiker (GDCh). Furthermore, the EUROMAR will be accompanied for the first time by the 8th European Federation of EPR Groups Meeting, a triennial meeting of all European EPR Groups and the Meeting of the International EPR Society.

The conference will cover all aspects of magnetic resonance spectroscopy such as methodological and technical advancements as well as new areas of application in material and life sciences, physics, chemistry and biology. Registration and abstract submission are open now. For further details please visit www.euromar2011.org.

EPR detected polarization transfer between GD3+ and protons at low temperature and 3.3T: The first step of dynamic nuclear polarization

Nagarajan V. et al., EPR detected polarization transfer between Gd3+ and protons at low temperature and 3.3 T: The first step of dynamic nuclear polarization, J. Chem. Phys., 2010, 132, 214504

http://dx.doi.org/10.1063/1.3428665

Electron-electron double resonance pulsed electron paramagnetic resonance (EPR) at 95 GHz (3.3 T) is used to follow the dynamics of the electron spin polarization during the first stages of dynamic nuclear polarization in solids. The experiments were performed on a frozen solution of Gd+3 (S=7/2) in water/glycerol. Focusing on the central |−1/2>→|+1/2> transition we measured the polarization transfer from the Gd3+ electron spin to the adjacent 1H protons.

The dependence of the echo detected EPR signal on the length of the microwave irradiation at the EPR “forbidden” transition corresponding to an electron and a proton spin flip is measured for different powers, showing dynamics on the microsecond to millisecond time scales. A theoretical model based on the spin density matrix formalism is suggested to account for this dynamics. The central transition of the Gd3+ ion is considered as an effective S=1/2 system and is coupled to 1H (I=1/2) nuclei. Simulations based on a single electron-single nucleus four level system are shown to deviate from the experimental results and an alternative approach taking into account the more realistic multinuclei picture is shown to agree qualitatively with the experiments.

EPR detected polarization transfer between GD3+ and protons at low temperature and 3.3T: The first step of dynamic nuclear polarization

Nagarajan V. et al., EPR detected polarization transfer between Gd3+ and protons at low temperature and 3.3 T: The first step of dynamic nuclear polarization, J. Chem. Phys., 2010, 132, 214504

http://dx.doi.org/10.1063/1.3428665

Electron-electron double resonance pulsed electron paramagnetic resonance (EPR) at 95 GHz (3.3 T) is used to follow the dynamics of the electron spin polarization during the first stages of dynamic nuclear polarization in solids. The experiments were performed on a frozen solution of Gd+3 (S=7/2) in water/glycerol. Focusing on the central |−1/2>→|+1/2> transition we measured the polarization transfer from the Gd3+ electron spin to the adjacent 1H protons.

The dependence of the echo detected EPR signal on the length of the microwave irradiation at the EPR “forbidden” transition corresponding to an electron and a proton spin flip is measured for different powers, showing dynamics on the microsecond to millisecond time scales. A theoretical model based on the spin density matrix formalism is suggested to account for this dynamics. The central transition of the Gd3+ ion is considered as an effective S=1/2 system and is coupled to 1H (I=1/2) nuclei. Simulations based on a single electron-single nucleus four level system are shown to deviate from the experimental results and an alternative approach taking into account the more realistic multinuclei picture is shown to agree qualitatively with the experiments.

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