Organic Radical Ions as Studied by Epr Spectroscopy

Gerson, Fabian

doi:10.1142/9789812816764_0019

Cited by 2 publications

(2 citation statements)

References 91 publications

(157 reference statements)

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“…In contrast, the monoanionic tetrakis(organogallium) cluster exhibits an EPR spectrum which can be simulated within the above mentioned line width limitation by assuming the coupling of the unpaired electron with four equivalent or virtually equivalent metal centers. It may be speculated that the extent (or type) of distortion from (spectroscopic) T d symmetry is different for [(RIn) 4 ] •- and [(RGa) 4 ] •- , resulting in a complete spin delocalization over the four gallium centers for the latter system (valence averaging, formal oxidation state +0.75) …”

Section: Electrochemistry and Epr Of The Cluster Compoundsmentioning

confidence: 99%

Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe₃)₃] and the Electrochemical Behavior of Ga₄[C(SiMe₃)₃]₄ and In₄[C(SiMe₃)₃]₄ with EPR Evidence for a Ga₄R₄ Radical Anion

Haaland¹,

Martinsen²,

Volden³

et al. 1996

Organometallics

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The gallium(I) compound Ga4[C(SiMe3)3]4 (1) with a tetrahedral Ga4 core in the solid state gives on evaporation the monomeric Ga(I) alkyl Ga[C(SiMe3)3] with the unique structural situation of a Ga atom solely coordinated by one singly bonded carbon ligand. Its molecular structure was determined now by gas-phase electron diffraction yielding a Ga−C bond length of 206.4(17) pm, similar to that found in the solid state for the tetramer and much longer than in compounds with gallium in the normal oxidation state of +3. As shown by cyclic voltammetry, 1 and the analogous cluster In4[C(SiMe3)3]4 (2) could both be reversibly reduced at about −2 V vs Fc+/0. Whereas the reduced organoindium tetramer did not exhibit any detectable EPR signals between 4 and 300 K, the gallium analogue showed an EPR spectrum compatible with the formulation [(RGa0.75) 4]•-; i.e. the unpaired electron was found to be delocalized over all four metal centers (a(69Ga) = 1.93 mT, a(71Ga) = 2.45 mT, 4 Ga).

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Section: Electrochemistry and Epr Of The Cluster Compoundsmentioning

confidence: 99%

Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe₃)₃] and the Electrochemical Behavior of Ga₄[C(SiMe₃)₃]₄ and In₄[C(SiMe₃)₃]₄ with EPR Evidence for a Ga₄R₄ Radical Anion

Haaland¹,

Martinsen²,

Volden³

et al. 1996

Organometallics

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“…1 First EUCHEM Conference on “Chemical Aspects of Electron Spin Resonance” at the Royal Agricultural College in Cirencester (England), March 28–April 2, 1965, organized by David H. Whiffen (National Physics Laboratory, NPL, Teddington, Middlesex). Participants [ 1 ]: from left to right, 1st row, sitting: A. Horsfield (1), J.H. Freed (3), E. Warhurst (4), B.…”

Section: The Early Years Of the Endor Connectionmentioning

confidence: 99%

Jim Hyde and the ENDOR Connection: A Personal Account

2017

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In this minireview, we report on our year-long EPR work, such as electron–nuclear double resonance (ENDOR), pulse electron double resonance (PELDOR) and ELDOR-detected NMR (EDNMR) at X-band and W-band microwave frequencies and magnetic fields. This report is dedicated to James S. Hyde and honors his pioneering contributions to the measurement of spin interactions in large (bio)molecules. From these interactions, detailed information is revealed on structure and dynamics of macromolecules embedded in liquid-solution or solid-state environments. New developments in pulsed microwave and sweepable cryomagnet technology as well as ultra-fast electronics for signal data handling and processing have pushed the limits of EPR spectroscopy and its multi-frequency extensions to new horizons concerning sensitivity of detection, selectivity of molecular interactions and time resolution. Among the most important advances is the upgrading of EPR to high magnetic fields, very much in analogy to what happened in NMR. The ongoing progress in EPR spectroscopy is exemplified by reviewing various multi-frequency electron–nuclear double-resonance experiments on organic radicals, light-generated donor–acceptor radical pairs in photosynthesis, and site-specifically nitroxide spin-labeled bacteriorhodopsin, the light-driven proton pump, as well as EDNMR and ENDOR on nitroxides. Signal and resolution enhancements are particularly spectacular for ENDOR, EDNMR and PELDOR on frozen-solution samples at high Zeeman fields. They provide orientation selection for disordered samples approaching single-crystal resolution at canonical g-tensor orientations—even for molecules with small g-anisotropies. Dramatic improvements of EPR detection sensitivity could be achieved, even for short-lived paramagnetic reaction intermediates. Thus, unique structural and dynamic information is revealed that can hardly be obtained by other analytical techniques. Micromolar concentrations of sample molecules have become sufficient to characterize stable and transient reaction intermediates of complex molecular systems—offering exciting applications for physicists, chemists, biochemists and molecular biologists.

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Organic Radical Ions as Studied by Epr Spectroscopy

Cited by 2 publications

References 91 publications

Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe₃)₃] and the Electrochemical Behavior of Ga₄[C(SiMe₃)₃]₄ and In₄[C(SiMe₃)₃]₄ with EPR Evidence for a Ga₄R₄ Radical Anion

Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe₃)₃] and the Electrochemical Behavior of Ga₄[C(SiMe₃)₃]₄ and In₄[C(SiMe₃)₃]₄ with EPR Evidence for a Ga₄R₄ Radical Anion

Jim Hyde and the ENDOR Connection: A Personal Account

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Organic Radical Ions as Studied by Epr Spectroscopy

Cited by 2 publications

References 91 publications

Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe3)3] and the Electrochemical Behavior of Ga4[C(SiMe3)3]4 and In4[C(SiMe3)3]4 with EPR Evidence for a Ga4R4 Radical Anion

Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe3)3] and the Electrochemical Behavior of Ga4[C(SiMe3)3]4 and In4[C(SiMe3)3]4 with EPR Evidence for a Ga4R4 Radical Anion

Jim Hyde and the ENDOR Connection: A Personal Account

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Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe₃)₃] and the Electrochemical Behavior of Ga₄[C(SiMe₃)₃]₄ and In₄[C(SiMe₃)₃]₄ with EPR Evidence for a Ga₄R₄ Radical Anion

Gas-Phase Structure of the Monomeric Alkylgallium(I) Compound Ga[C(SiMe₃)₃] and the Electrochemical Behavior of Ga₄[C(SiMe₃)₃]₄ and In₄[C(SiMe₃)₃]₄ with EPR Evidence for a Ga₄R₄ Radical Anion