Spin-dependent delocalization

Spin density, Fe—S dimers, 38 443-445 Spin-dependent delocalization, 47 39 Spin echo studies, photosystem II, 33 233-234 Spin eigenfunctions, 38 427 Spinels, 4 155, 20 143, 144 arrangement, 2 29-33 crystal structure of, 4 153 neutron diffraction studies on, 8 249-250 substitution of oxygen by fluorine, 20 145, 146... 

We are therefore faced here with radical complexes which easily distort depending on the structural arrangement and whose SOMO is different for every crystal structure associated with a given counter-ion, a very original feature in these series. The unfolded d1 complexes can be described as Mo(IV) complexes with a spin density essentially localized on the dithiolene ligand while the more folded complexes have a stronger metal character. This variable spin density delocalization is expected to influence strongly the amplitude and dimensionality of intermolecular interactions between radical species in the solid state, as detailed below in Sect. 3. 

The yield of alcohol ROH depends on the nucleophility of the radical as well as on the degree of the delocalization of an unpaired dectron. If the unpaired electron is not ddocalized, the reactivity of the n-alkyl radical increases with its nucleophility which may be correlated with the ionization potential. On the other hand, if the unpaired spin is delocalized, the orbital overlap of the radical and the peroxidic oxygen becomes an important reactivity factor. A radical seemingly... 

Polarization, charge distribution or atomic coefficients of the C-O bond are decisive for heterolytic bond splitting by nucleophiles [21]. Homolytic bond splitting, instead, is related to radical stability and reactivity, which in turn depends on spin density, spin polarization, delocalization of the free electron and hyper-oconjugation [22, 23]. Essential to all these radical reactions is the one-electron transfer from the trigger, typically under photochemical [24], (in the presence of sensitizer) [25], or electrochemical conditions [26]. 

Thermolysis rates ( j) of dialkyldiazenes (15) show a marked dependence on the nature of R (and R ). The values of k< increase in the series where R (=R ) is ary <primaryfree spin of the incipient radical.49 For example, Timberlake7 has found that for the case of dialkyldiazenes,... 

A good correlation with ordinary Hammett a values was based on 16 well-behaved substituents, and p-SOMe conformed well to this. Various other substituents showed deviations which were attributed to enhanced + R effects. These included p-SPh and this was explained in terms of 7t(pd) bonding, which was thus taken to play no part in the effect of p-SOMe on the methyl hyperfine splitting. More recently several 4-substituted benzyl radicals of the type RSO C6H4CH2 (n — 0,1 or 2 R = Me, Ph, Tol, COMe or OMe) have been examined by ESR spectroscopy249. The ability to delocalize spin density onto the substituent decreases in general as n increases and the effect of R depends on the oxidation state of sulfur. These authors have devised a new scale of substituent effects (sigma dot... 

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