Intervalence radicals

Electron transfer reactions within a- and 7t-bridged nitrogen-centered intervalence radical ions, 41, 185... 

Electron transfer, in thermal and photochemical activation of electron donor-acceptor complexes in organic and organometallic reactions, 29, 185 Electron transfer, long range and orbital interactions, 38, 1 Electron transfer reactions within s- and p-bridged nitrogen-centered intervalence radical ions, 41, 185... 

The effects of temperature on the shape of intervalence charge-transfer bands for the radical cations of bis(2-f-butyl-2,3-diazabicyclo[2.2.2]oct-3-yl)hydrazines that are bridged by 2,5-xylene-1,4-diyl, durene-l,4-diyl, naphthalene-1,4-diyl, biphenyl-4,4-diyl and 9,9-dimethylfluorene-2,7-diyl aromatic rings were studied by ESR. ... 

Extended Hueckel MO calculations (Kirchner et al. 1976) support the formulation that the unpaired electron is delocalized over both metallocene residues in the bis(ful-valeneiron) cation radical. Alternatively, very fast intraionic intervalence electron transfer may take place between the formal Fe(II) and Fe(III) atoms. 

Temperature Effects on Electron Transfer within Intervalence Bis(Hydrazine) Radical Cations. 

The copper(I) alkynyls displayed rich photochemistry and particularly strong photoreducing properties. The transient absorption difference spectrum of [Cu3(dppm)3(/X3-) -C=CPh)2]+ and the electron acceptor 4-(methoxycarbonyl)-A-methylpyridinium ion showed an intense characteristic pyridinyl radical absorption band at ca. 400 nm. An additional broad near-infrared absorption band was also observed and it was assigned as an intervalence-transfer transition of the mixed-valence transient species [Cu Cu Cu (dppm)3(/x3- -C=CPh)2] +. The interesting photophysical and photochemical properties of other copper(I) alkynyl complexes such as [Cu(BTA)(hfac)], 2 [Cui6(hfac)8(C=C Bu)8], and [Cn2o(hfac)8(CsCCH2Ph)i2] have also been studied. 

Ferrocenyl derivatives of 73, namely (Co3(CO)9 L (/i3-CFc)] (n = 0-3, L = phosphine or phosphite) undergo reversible reduction at the tricobalt center to detectable radical anions (n = 0), and oxidation at the iron center to give isolable cations (182). For the trisubstituted derivatives [ = 3, L = P(OMe)3 or P(OPh)3], the monocations appear to be mixed-valence species in which the two redox sites are weakly interacting low-energy absorption bands, assigned to intervalence transfer transitions, have been observed. The dications (Co3(CO)6 P(OR)3 3(/i3-CFc)] (R = Me or Ph) are also isolable, oxidation having occurred at both possible redox sites (183). 

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