E.s.r study of non-alternant radical ions

1965 ◽  
pp. 488 ◽  
Author(s):  
F. Gerson ◽  
J. Heinzer
Keyword(s):  
Radical Ions ◽  
Alternant Radical

Untersuchung von einfachen π-Elektronensystemen mit Hilfe von Elektronenspin-Resonanz und Polarographi

1965 ◽  
Vol 20 (9) ◽  
pp. 1102-1116 ◽  
Author(s):  
K. MöBius
Keyword(s):  
Negative Ion ◽  
Excess Charge ◽  
Radical Ions ◽  
Charge Effects ◽  
Half Wave ◽  
High Dielectric ◽  
Better Than ◽  
Alternant Radical ◽  
Spin Densities ◽  
G Factors

In order to test the results of the MO-theories of HÜCKEL and MCLACHLAN, spin densities and energies of unpaired electrons of 10 aromatic hydrocarbon radicals have been measured by EPR and polarography. Eight negative ion radicals have been prepared electrolytically in solvents of high dielectric constant. This technique is found to yield “free” solvated radical ions with spin densities and π-orbital energies not noticeably affected by the medium. By eliminating solvent effects HÜCKEL values of the COULOMB and resonance integrals α0 and β0 of the free ions could be measured. They turn out to depend strongly on the sign of the excess charge. The measurements of the splitting constants indicate that the COLPA-BOLTON equation possibly overestimates charge effects on the σ-system at the expense of influences from non-neighbouring 2pz-AO’s. In the case of alternant radical ions the HÜCKEL MO’s are better than those derived by MCLACHLAN’S theory, though qualitatively McLACHLAN’S theory predicts negative spin densities correctly. The g-factor measurements, which are accurate within 2 ppm, confirm the linear relation between Δg and the HÜCKEL coefficient m0 of the lowest halfoccupied π-orbital recently deduced by STONE. On the other hand neutral odd-AH-radicals have g-factors about 4 · 10-5 smaller than the theoretical values for m0=0. A linear dependence has been found between Δg and the half-wave potential U½ which provides the possibility to measure g-factors with an accuracy of about 10 ppm by measuring U½-values. This method enables one to measure g-factors even for those AH-radical ions which could not yet be detected by EPR.

Properties and Reactivity of First and Second Row Hydrides. IV. Interactions Between Hydrides and Their Radical Ions

1993 ◽  
Vol 58 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Rudolf Zahradník
Keyword(s):  
Radical Cations ◽  
Stabilization Energy ◽  
Hydrogen Atom Abstraction ◽  
Type Ii ◽  
Radical Ions ◽  
Reaction Products ◽  
Ion Molecule Reactions ◽  
Heats Of Reaction ◽  
Experimental Values ◽  
Easy Differentiation

The energies and heats of ion-molecule reactions have been calculated (MP4/6-31G**//6-31G** or better level) and compared with the experimental values obtained from the heats of formation. Two main types of reactions have been studied: (i) AHn + AHn+• ↔ AHn+1+ + AHn-1• (A = C to F and Si to Cl), (ii) AHn + BHm+• ↔ AHn+1+ + BHm-1• or AHn-1+• + BHm+1+ (A and B = C to F). In contrast to (i), processes of type (ii) permit easy differentiation between the proton transfer and hydrogen atom abstraction mechanisms. A third type of interaction involves reactions with radical anions (A = Li to F); comparison was made with analogous processes with radical cations. A brief comment is made about the influence of the level of computational sophistication on the energies and heats of reaction, as well as on the stabilization energy of a hydrogen bonded intermediate, a structure which is similar to that of the reaction products.

Structure and Reactivity of Radical Ions: New Twist on Old Concepts

ChemInform ◽  
2006 ◽  
Vol 37 (52) ◽  
Author(s):  
Patrick J. Donoghue ◽  
Olaf Wiest
Keyword(s):  
Radical Ions

Chemical Insights from EPR Spectra of Organometallic Radicals and Radical Ions

ChemInform ◽  
2004 ◽  
Vol 35 (18) ◽  
Author(s):  
Anne L. Rieger ◽  
Philip H. Rieger
Keyword(s):  
Epr Spectra ◽  
Radical Ions

Bestimmung von innermolekularen Torsionswinkeln aus Hyperfeinstruktur-Aufspaltungen und g-Faktoren

1965 ◽  
Vol 20 (9) ◽  
pp. 1117-1121 ◽  
Author(s):  
K. Möbius
Keyword(s):  
Electron Diffraction ◽  
Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbons ◽  
Small Amplitude ◽  
Membered Ring ◽  
Radical Ions ◽  
Hydrogen Atoms ◽  
Stereochemical Structure ◽  
X Ray ◽  
Phenyl Rings

The stereochemical structure of aromatic hydrocarbons in solution being overcrowded with hydrogen atoms is not known with certainty, because the conventional X-ray and electron diffraction methods are suitable only for samples in the crystalline and vapor phase. Using EPR spectroscopy for the aromatic hydrocarbon radicals biphenyl (—), phenanthrene (—) and pentaphenylcyclopentadienyl (PPCPD) innermolecular twist and bond angles could be determined by means of hfssplittings and g-factors. Stably solvated biphenyl radical ions are found to have twist angles of 38 ±2°; phenanthrene ions turn out to be planar but change their angles of hybridization at particular positions; in the PPCPD radical the phenyl rings oscillate with small amplitude around planes orthogonal to the five-membered ring.

Inorganic Radical-ions and Their Organic Reactions

1979 ◽  
Vol 48 (11) ◽  
pp. 1055-1075 ◽  
Author(s):  
A F Morkovnik ◽  
O Yu Okhlobystin
Keyword(s):  
Organic Reactions ◽  
Radical Ions
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