Fullerene derivatives energy transfer

Guldi D M, Hungerbuhler H and Asmus K-D 1999 Inhibition of oluster phenomena in truly water soluble fullerene derivatives bimoleoular eleotron and energy transfer prooesses J. Phys. Chem. A 103 1444-53... 

Guldi DM, Hungerbuhler H, Asmus KD (1999) Inhibition of cluster phenomena in truly water soluble fullerene derivatives bimolecular electron and energy transfer processes. Journal of Physical Chemistry B 103 1444-1453. 

Koeppe R, Sariciftci NS (2006) Photoinduced charge and energy transfer involving fullerene derivatives. Photochemical and Photobiological Sciences 5 1122-1131. 

The Sc -promoted photoinduced electron transfer can be generally applied for formation of the radical cations of a variety of fullerene derivatives, which would otherwise be difficult to oxidize [135]. It has been shown that the electron-transfer oxidation reactivities of the triplet excited states of fullerenes are largely determined by the HOMO (highest occupied molecular orbital) energies of the fullerenes, whereas the triplet energies remain virtually the same among the fullerenes [135]. 

In this chapter we have described the photophysics and photochemistry of C6o/C70 and of fullerene derivatives. On the one hand, C6o and C70 show quite similar photophysical properties. On the other hand, fullerene derivatives show partly different photophysical properties compared to pristine C6o and C70 caused by pertuba-tion of the fullerene s TT-electron system. These properties are influenced by (1) the electronic structure of the functionalizing group, (2) the number of addends, and (3) in case of multiple adducts by the addition pattern. As shown in the last part of this chapter, photochemical reactions of C60/C70 are very useful to obtain fullerene derivatives. In general, the photoinduced functionalization methods of C60/C70 are based on electron transfer activation leading to radical ions or energy transfer processes either by direct excitation of the fullerenes or the reaction partner. In the latter case, both singlet and triplet species are involved whereas most of the reactions of electronically excited fullerenes proceed via the triplet states due to their efficient intersystem crossing. 

It is found that, upon irradiation in toluene, a highly efficient triplet-triplet energy transfer governs the deactivation of the RuP, while electron transfer from the porphyrin to the fullerene (RuP +-C6o ) prevails in polar solvents [389]. Complexation of ZnP by the fullerene derivative is reversible and, following excitation of the ZnP, gives rise to very efficient charge separation. In fluid polar solvents like THE and benzonitrile radical ion pairs (ZnP +-C6o ) are generated both by intramolecular electron transfer in the complex and by intermolecular electron transfer in the uncomplexed form [386]. In the latter case radical pairs live about 10 ps in THE and about 50 ps in benzonitrile at room temperature [386]. Thus, com-... 

The nature of the lowest-lying excited states of the fullerenes has been difficult to identify with much certainty. From Shpol skii-type luminescence spectra recorded at 1.5 K it has been concluded that the first-excited singlet state in C70 is of A 2 character. The origins of the lowest energy transitions in Ceo, namely Si(T]g) and S2(Gg), have been assigned on the basis of fluorescence and excitation spectra, supported by theoretical calculations. " The luminescence properties and relaxation dynamics of single crystals of Qo have been described while related measurements have been made for solid films of Ceo " Similar studies have reported the luminescence spectral properties of 50 trapped inside the cavities of NiY zeolites. An analysis of the fine structure of electron-vibrational spectra has been made for 50 and its derivatives in a solid toluene matrix. The rate of triplet energy transfer between fullerenes in toluene solution has been measured as a function of temperature and used to derive thermodynamic parameters for the transfer process. ... 

Perfluorinated BSubPc bearing axial m-formylphenoxy group 196 [99] was used for preparation conjugates with fullerene (Scheme 51) as tunable molecular scaffolds for intramolecular electron and energy transfer processes [110]. The azome-thine ylide formed by treatment of the formyl derivative 196 with A -methylglycine gives the conjugate with fullerene 197 (44 %) in a dipolar 1,3-cycloaddition (Prato reaction). 

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