| Abstract
| - Radical cations and dications of three bishydrazines belonging to the Class II mixed valence compoundshave been generated, either spontaneously or by oxidation with AgSbF6, in two 1-butyl-3-methylimidazolium(4+) ionic liquids having BF4- and PF6- as counterions. The optical spectra of these intermediates haveallowed evaluation of Marcus' reorganization energy λs, a parameter that is directly proportional to the solventpolarity. Remarkable differences in λs, as large as 600 cm-1, have been observed as a function of the counterion,with these data providing support for the observed differences between both ionic liquids (4+BF4- and 4+PF6-)in catalysis. However, in terms of polarity, the λs values rank the hydrophilic 4+BF4- as being similar todimethyl sulfoxide and dimethylformamide, while the polarity of hydrophobic 4+PF6- is analogous toacetonitrile. Overall, our results indicate that ionic liquids are not exceptional liquids in terms of polarity.
|
