Paramagnetic rings cation radicals

Goff and coworkers extensively used paramagnetic NMR in identifying the nature of coupling present between the unpaired electron present on the metal and porphyrin ring in metalloporphyrin it-cation radicals [224-228], NMR spectroscopy does probe the environment of protons at the extreme periphery of... 

In a preliminary ESR study of this reaction, the fact that the equimolar addition of XV to a DMF solution of CuCU imder argon quenched the Cu(II) paramagnetic signals, indicates occurrence of one electron transfer from XV to Cu(II) to give a cation radical and Cu(I). Copper(I) is then proposed to react with dioxygen to give the Oi species which may react with the ring cleaved product as schematically depicted below, equation (112). 

The product is a black-brown solid that is very sensitive to oxygen. The same cation can be obtained by oxidation of S4N4 with AsFs and is unusual in being the only sulfur-nitrogen (paramagnetic) radical that has been obtained as a stable crystalline salt. X-ray diffraction analysis shows the structure to be a planar 5-membered ring with approximate... 

When the dithiole ring is annelated by phenalene, the laws of valence require the resultant aromatic heterocycle to be cationic reduction thus gives the neutral phenaleno[l,9-c(/][l,2]dithiolyl radical (138). This persistent radical has been examined in solution and its hyperfine splittings assigned on the basis of MO calculations. The radical is remarkably stable against dimerization it may be isolated as a paramagnetic solid whose mass... 

In some cases, the identity of paramagnetic "satellite ions" was established by ODMR [42,44,48]. For example, 9,10-octalin + was identified in decalins and their solutions [42]. ODMR spectra of "satellite ions" in cyclohexane were related to EPR spectra of matrix-isolated cyclohexene + (Note that in the liquid cyclohexane, cyclohexene + undergoes a fast ring-puckering motion that averages hyperfine coupling constants for equatorial and axial protons, so the the EPR spectra of cyclohexene + in liquid and solid matrices are different) [42,44,48]. In both of these cases, the olefin radical cations were formed in spurs rather than in a reaction of the solvent hole with the olefin in the solvent bulk [42] (octalins gradually accumulate as radiolytic products). Olefin "satellite ions" were also observed in squalane [24]. 

According to the mechanism, the extent of CO2 reduction (and the consequent kind of products) is determined by the reduction ability of the anionic form of the complex and the stability of the intermediate products . On the other hand, the difference in the ability to produce methane between the amino and the butyl Cu phthalocyanine indicates the strong dependence of the reduction on the substituents in the phthalocyanine ring. Then the mechanism is based on the strong reducing behavior of the reduced form of CuPc. Then in the first stage, the reduced complex can transform CO2 in the radical cation and some amount of this radical becomes HCOOH whereas another coordinates with the Cu center (paramagnetic). After various steps, the coordinated radical anion terms into CO. If the adduct is sufficiently stable, the consecutive reduction steps permits the transfor-... 

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