Electronic and Vibrational Spectra of Fullerenes in Contact with Oxygen

Abstract

The high-resolution electronic and vibrational spectra of fullerenes C60, C70, and C78 were analyzed. The absorption spectrum of fullerene C60 contains a series of seven well-resolved bands in the range 200-280 nm, the strongest of them being at 240 nm, as well as two broadened bands of lower intensity at 280 and 330 nm. The former seven bands were assigned to vibrationally excited π-π* transitions in the molecular system of conjugated π bonds, and the latter two, to intermolecular interactions in a fullerene-oxygen contact complex. As the molecular weight of the fullerene increases, the short-wave absorption band suffers a hypsochromic shift, which is characteristic of nonalternant aromatic systems. The IR spectra provide evidence for the formation of a contact charge-transfer complex with oxygen by displaying emission and absorption in the region of fundamental frequencies of the triplet, singlet, radical-ion, and ionic states of molecular oxygen.