Oxidation dications

In Chapter 11 (the only chapter in the volume that focuses on persistent oxidation dications), N. S. Mills discusses the fluorenylidene dications and their antiaromatic character. 

Earlier progress in these studies has been summarized in reviews published in the last decade, emphasizing carbocations and oxidation dications, RCs, as well as reactive intermediates from the nitro- and nitroso-derivatives. The review article published in 1996 emphasized groundwork studies on protonation as well as oxidation (both RCs and stable dications) of polycyclic arenes and explored possible relationships between charge distribution and carcinogenicity, in concert with its... 

In another study, the arenium ions of protonation and the two-electron oxidation dications derived from BaP and three of its nonalternant isomers, namely, azu-leno[5,6,7-c phenalene 69 (a strong carcinogen reported to be as potent as BaP), azuleno[l,2,3-cJ phenalene 70 (a strong mutagen/weak carcinogen), and... 

The mono- and diprotonated carbocations and the two-electron oxidation dications derived from parent pyrene and its nonalternant isomers azupyrene (dicyclo-penta[e/, /]heptalene) (DCPH) 72 and dicyclohepta[eJ,g /z]pentalene (DCHP) 73 were studied at the B3LYP/6-31G(d) level (Fig. 29). The most likely site(s) for mono-and diprotonation were determined based on relative arenium ion energies and the structures of the energetically most favored carbocations were determined by... 

Arenium ion energies (AAH ion - neutral) and changes in carbon charges [Aq = (ion) - q (neutral)] for protonation of 90 and 91 were probed by the AMI method. The singlet oxidation dication of 90 was also calculated. The charge delocalization modes in the PAH arenium ions were discussed and compared. The AMI studies indicated that benzo[<3]coronene cations were less delocalized than benzo[g/z/]perylene ions. Benzannelation (91 92) severely limited the conjugation path in the carboca-tions despite the fact that coronene 92 was still planar. Further benzannelation (92 90) had a minimal effect on the charge delocalization mode. 

Diprotonation of (97) with H2SO4 gives a species which is protonated at both carbonyl groups, not the delocalized annulene dication, presumably for steric reasons.140 Oxidation dications of perylenes, e.g. (98), are [4n + 2] species with diamagnetic ring currents, whereas the dibcnzo[ /. // ] derivative [two more benzene rings at the top and... 

The ease of oxidation of polycyclic aromatic hydrocarbons in the gas phase481 as well as in solution is well-documented.482 195 In strong acid solutions, monopositive radical ions and/or dipositive ions, also known as oxidation dications, have been reported.271,494,495 Similar species have been observed in anodic oxidations of... 

Reactions with Parting of Radicals. The one-electron oxidation of cationic dyes yields a corresponding radical dication. The stabihty of the radicals depends on the molecular stmcture and concentration of the radical particles. They are susceptible to radical—radical dimerization at unsubstituted, even-membered methine carbon atoms (77) (Fig. 6). 

It is a volatile orange-red crystalline solid (m.p. 30°C), stable to over 100°C. On reduction with tertiary phosphines or sodium amalgam, Os(NBu )3 is formed, which is dimeric (ButN)2Os(/x-NBut)2Os(NBu )2. This can be oxidized to the osmium(VII) dication with concomitant shortening in the Os-Os distance from 3.1 to 2.68 A. 

No oxidation toFem dication in concentrated KjSO or NaOH/HjOj... 

Figure 2. Radical cations (polarons) and dications (bipolarons) obtained by oxidation of the neutral chain. The rotated angles and counter-ions needed to retain electroneutrality are not shown.

Cationic polymerization of ethylene oxide is accompanied by depolymerization and oligomerization. It has been reported that ethylene oxide polymerized cation-ically with the living dication of tetrahydrofuran and a surface active material was obtained290. ... 

Detailed kinetic studies in connection with digital simulations do confirm the RR coupling mechanism postulated in older publications as well as the oxidation of the resulting dimer D to the dication D. But the surprising drop in the height of the reduction wave for the redox pair as the concentration... 

The chemical oxidation of [MnLj]Y is well known. These voltammetric data suggested some of the other species might be successfully oxidized indeed [Mn(CO)(CNCHj)5]PF5 was found to be oxidized to [Mn(CO)-(CNCH3)s](PFj)2 by nitric acid 154). The expected shift of vco cn to higher frequencies in the dication is noted. Chemical oxidation to an MnLj " species could not be accomplished, however. 

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