Donor electron spin

There have been no reports of complexes of " JV-substituted thiosemicarbazones derived from 2-formylpyridine, but 2-acetylpyridine JV-methyl-thiosemicarbazone, 3a, formed [Fe(3a-H)2]C104 and [Fe(3a-H)2]FeCl4 [117]. The nature of these two species was established by partial elemental analyses, molar conductivities, magnetic moments, electronic, infrared, mass and electron spin resonance spectra. A crystal structure of a related selenosemicarbazone complex confirmed the presence of a distorted octahedral iron(III) cation coordinated by two deprotonated anions so that each ligand is essentially planar and the azomethine nitrogens are trans to each other the pyridyl nitrogen and selenium donors are both cis. 

Electron donor-acceptor complexes, electron transfer in the thermal and photochemical activation of, in organic and organometallic reactions, 29, 185 Electron spin resonance, identification of organic free radicals, 1, 284 Electron spin resonance, studies of short-lived organic radicals, 5, 23 Electron storage and transfer in organic redox systems with multiple electrophores, 28, 1... 

The 29Si relaxation rate 7j"1 at 1.6 K vs donor concentration nD shows a sharp decrease between nD = 2.5 x 1018 cm 3 and nu = 6 x 1018 cm 3. This reflects the fact that in the semiconducting regime (lower donor concentrations), the unionized donors are paramagnetic point sources of relaxation for the 29Si nuclei. Their localized electron spins are more effective in inducing relaxation than the itinerant electrons found in a conduction band at the higher donor concentrations [18]. 

Electrochemical methods for the generation of anion-radicals consist of potential-controlled electrolysis. The control of a potential allows one to detain rednction just after a one-electron transfer to a depolarizer. The one-electron natnre of the electron transfer is coincidentally inspected by means of coulombometry. One molecnle mnst consnme one electron. If less than one electron is consumed in the framework of the one-electron rednction, it means that the yield of an anion-radical is not quantitative. The electrolysis in a special amponle placed into a resonator of the electron spin resonance (ESR) spectrometer permits one to identify many nnstable anion-radicals. The electrochemical methods of anion-radical generation employ an electrode as an electron donor. 

Electron-pair donor (or Lewis base), NUCLEOPHILE ELECTRON SINK ELECTRON SPIN RESONANCE ELECTRON TRANSEER MARCUS EQUATION ELECTRODE KINETICS Electron transfer mechanism,... 

The reaction involves the transfer of an electron from the alkali metal to naphthalene. The radical nature of the anion-radical has been established from electron spin resonance spectroscopy and the carbanion nature by their reaction with carbon dioxide to form the carboxylic acid derivative. The equilibrium in Eq. 5-65 depends on the electron affinity of the hydrocarbon and the donor properties of the solvent. Biphenyl is less useful than naphthalene since its equilibrium is far less toward the anion-radical than for naphthalene. Anthracene is also less useful even though it easily forms the anion-radical. The anthracene anion-radical is too stable to initiate polymerization. Polar solvents are needed to stabilize the anion-radical, primarily via solvation of the cation. Sodium naphthalene is formed quantitatively in tetrahy-drofuran (THF), but dilution with hydrocarbons results in precipitation of sodium and regeneration of naphthalene. For the less electropositive alkaline-earth metals, an even more polar solent than THF [e.g., hexamethylphosphoramide (HMPA)] is needed. 

CH3CN, dimethylsulfoxide, dimethylfor-mamide (DMF) and pyridine, of course, is reversible at the timescale of cyclic voltammetry the first unambiguous studies appeared in 1965, the radical being identified by electron spin resonance (ES R) [34, 35]. The reversibility has been demonstrated by cyclic voltammetry in pyridine even in a basic medium, the second reduction step occurring at a much more negative potential is irreversible [36]. In the presence of proton donors, and, of course, in protic solvents, it is known that O is unstable and that the reduction of O2 proceeds via a two-electron step [10, 27, 37]. The superoxide ion is moderately basic... 

The impact on the electronic structure affecting the oxidation potential and the electron spin distribution has been explained within a simple molecular orbital (MO) model.189 199 As in the bRC the formation of a dimer leads to a decrease of the oxidation potential of the primary donor ( see section 2.1). 

Suppose a donor electron occupies an s-like state, e.g., an at state for a center with tetrahedral symmetry. Such a state is orbitally nondegenerate, but may accomodate two electrons, with opposite spins. Thus, the zero-electron... 

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