Organic anions, delocalized

Lithium Salts Based on Heterocyclic Anions. Lithium salts based on organic anions where the formal charge is delocalized throughout substituted heterocyclic moieties were also reported sporadically, which included, for example, lithium 4,5-dicyano-l,2,3-triazolate ° and lithium bis(trifluoro-borane)imidazolide (Lild). ° The former was developed as a salt to be used for polymer electrolytes such as PEO, and no detailed data with respect to electrochemistry were provided, while the latter, which could be viewed as a Lewis acid—base adduct between LiBp4 and a weak organic base, was intended for lithium ion applications (Table 13). 

E. Organomagnesium Compounds with Delocalized Organic Anions. . 195... 

It is even possible to have a negative charge of an organic acid delocalized over three atoms-as in the anions of the sulfonic acids. Methanesulfonic acid has a p/C , of -1.9. 

This sort of delocalization stabilizes the ion in fact, the C13C00- anion is more stable than the parent molecule, CI3COOH. For this reason, the solvated anion resides in solution in preference to the acid. Ka is therefore large, making trichloroacetic acid one of the strongest of the common organic acids. 

It shonld also be mentioned that there are some cases when the cation-selective solvation promotes greater n-electron delocalization in the remaining free anion-radicals (see Section 3.2.5). Staley et al. (1999) and Staley and Kehlbeck (2001) studied the phenomenon for organic dianions too. Snch a solvent effect leads to changes in reactivity of these species. 

The characterization of the semiquinone radical anion species of PQQ in aprotic solvents was undertaken to provide information about the electrochemistry of coenzyme PQQ and to give valuable insight into the redox function of this coenzyme in living systems <1998JA7271>. The trimethyl ester of PQQ and its 1-methylated derivative were examined in aprotic organic solvents by cyclic voltammetry, electron spin resonance (ESR), and thin-layer UV-Vis techniques. The polar solvent CH3CN was found to effectively solvate the radical anion species at the quinone moiety, where the spin is more localized, whereas the spin is delocalized into the whole molecule in the nonpolar solvent CH2CI2. 

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