Electron Affinities and Half-Wave Reduction Potentials

5 ELECTRON AFFINITIES AND HALF-WAVE REDUCTION POTENTIALS 

The first experimental method for obtaining relative electron affinities was the measurement of half-wave reductions potentials in aprotic solvents. The electron affinities are related to the half-wave reduction potentials by a simple relationship 

When the ECD electron affinities were measured, the AAG for the aromatic hydrocarbons (2.0 eV) and the aromatic aldehydes and ketones (2.3 eV) were observed to be approximately constant within the class of molecules, but different from each other. The fiillerenes ( AAG = 1.76 eV) have a lower charge density and lower AAG than the majority of other compounds. With the determination of more gas phase electron affinities, the AAG values range from 1.7 eV for larger fullerenes to 2.7 eV for small anions [3, 10]. 

This may seem to involve merely grouping molecules according to their measured deviations. This would be true if there were no fundamental basis for the grouping. 

In 1970 the MINDO/3 and j/2 values were correlated with two parameters in the linear equation, )/2 = m (Ea) + b, to give a reported standard deviation of 0.028 eV. The slope was 0.92. In this data analysis outliers must have been statistically eliminated since some of the deviations are greater than 0.1 eV, three times the reported standard deviation. Using all the MINDO/3 Ea and a unit slope, we obtain an average A AG value of 1.94 0.08 eV. The greater deviation results from the use of one less parameter and all the data [26], 

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Ruoff RS, Kadish KM, Boulas P, Chen ECM (1995) Relationship between the electron affinities and half-wave reduction potentials of fullerenes, aromatic hydrocarbons, and metal complexes. J Phys Chem 99 8843-8850... 

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