Chapter 8: Electron-Transfer Processes of Fullerenes Studied with Time-Resolved Spectroscopies
Published:31 Oct 2011
Special Collection: 2011 ebook collection , 2011 ebook collection , 2011-2015 materials and nanoscience subject collectionSeries: Nanoscience & Nanotechnology
Photoinduced ET processes of fullerenes have been reviewed in this chapter on the basis of data collected from the optical time-resolved spectral methods such as fluorescence lifetime measurements and transient absorption spectra in wide wavelength and wide time regions. For mixture systems of fullerenes with electron-donor, the partitions of 1C60*/1C70* and 3C60*/3C70* depend on the donor concentration and solvent polarity as obtained by the transient spectra showing both the absorption bands of the reactants and the products without overlap. For many C60–donor diads, the radical ion pairs (C60˙−–donor˙+) have longer lifetimes compared with conventional acceptor–donor diads. This is reasonably interpreted by the inverted region of the Marcus parabola due to small reorganisation energy, in addition to the triplet-spin character of the radical ion pairs. When a second donor is attached to the original C60–donor diads, the lifetimes of the radical ion pairs are further prolonged due to the distant cation radical from the anion radical centre. When C60 and donor are connected with long-conjugated chains, distant charge-separation processes through the π-conjugated bridges become possible. Within the supramolecular assembly both through-bonds and through-space charge-separation processes take place. In the case of rotaxanes containing the fluctuating donor and acceptor, the through-space charge-separation process tends to take place via the triplet states. When C60 molecules are covalently embedded in the hole-transporting polymers, long-range hole migration along the polymer chain takes place. With these fundamental studies of photoinduced electron-transfer processes of the fullerene derivatives, many new aspects for photochemistry and photophysics are developing as summarised in this chapter.