The power of in situ ESR spectroelectrochemistry in the analysis of a C84 fullerene isomer

It is demonstrated for the C₈₄ fullerene molecule that the in situ ESR spectroelectrochemistry gives a clear insight into the isomeric purity of higher fullerenes and allows the detection of minor impurities whose presence is not found by other spectroscopic techniques. The monoanion of purified D_2d C₈₄:23 fullerene isomer was studied by ESR-spectroelectrochemistry in detail, resulting in a relatively broad ESR line because of the high symmetry of the fullerene cage. The minor impurity in the C₈₄ monoanion ESR spectrum, with a sharp line (ΔB_pp = 0.15 G) and g = 2.0009 which compose the 2% of the signal was identified as monoanion of the C₂ C₈₂:3 isomer. The second impurity in the D_2d C₈₄:23 is attributed to the C_s C₈₄:16 isomer which was neither found by NMR spectroscopy nor by cyclic voltammetry.