THE RELATIONSHIP BETWEEN THE ELECTRON-AFFINITIES AND HALF-WAVE REDUCTION POTENTIALS OF FULLERENES, AROMATIC-HYDROCARBONS, AND METAL-COMPLEXES

Abstract

Differences in energy for neutral molecule and negative ions upon going from the gas phase to solution, -Delta Delta G(sol), have been calculated from gas phase electron affinities and half-wave reduction potentials for a series of fullerenes, aromatic hydrocarbons, metalloporphyrins, and metal complexes in dimethylformamide (DMF). For those compounds with similar charge delocalization, the value of -Delta Delta G(sol) is constant and equal to 1.76 +/- 0.06 eV for the fullerenes, 1.99 +/- 0.05 eV for the aromatic hydrocarbons and the metalloporphyrins, and 2.19 +/- 0.14 eV for the metal acetylacetonates. The fullerenes form a new class of molecules in which the charge is highly delocalized, and this is demonstrated by the relatively low value of -Delta Delta G(sol). A procedure for determining adiabatic electron affinities from reduction potentials, and vice versa, is established. This procedure is applied to benzene to give an electron affinity of -0.7 +/- 0.14 eV, to La@C-82 to give an electron affinity of 3.21 +/- 0.06 eV, and to Y@C-82 to give an electron affinity of 3.32 +/- 0.06 eV. On the other hand, a value of E(1/2) = 0.09 +/- 0.14 V vs SCE is predicted for the reduction of Ca@C-60 in DMF based upon a reported electron affinity of 3.0 +/- 0.1 eV.