LONG TERM STUDY OF FULLERENE C60 RADICAL CATION BY ELECTRON SPIN RESONANCE (ESR)

Franco Cataldo, Susana Iglesias-Groth

Abstract


The dissolution of fullerene C60 in oleum (fuming sulphuric acid 20% free SO3) was followed simultaneously with ESR (Electron Spin Resonance) and NIR (Near Infrared  Spectroscopy). It is shown that the intensity of the ESR signal associated to the formation of C60 radical cation (C60+• ) follows the same kinetics of the NIR absoption band at about 938 nm. Thus, the band at about 938 nm represents the optical counterpart of the ESR signal of C60+• . After the formation of C60+•, the evolution of the ESR spectrum and its optical counterpart in the NIR suggests the formation of other fullerene oxidation products. These products were recovered from the oleum solution and analyzed with FTIR and found to be fullerol (hydroxylated derivative of fullerene). The work-up led to the desulfonation of the substrate. The ESR signal of C60 in oleum was followed for two weeks. Even after so long time, the ESR signal appeared strong and clear although under slow decay. Thus, the oxidation species of C60+• (polycations, dimers and oligomers of C60, sultonated and sulfated derivatives) are persistent radicals in oleum.

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DOI: http://dx.doi.org/10.17628/ecb.2014.3.920-924

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