Principles and Perspectives of Fullerene Chemistry

Since all the C atoms of fullerenes are quarternary, and therefore contain no hydrogens, substitution reactions characteristic for planar aromatics are not possible 

Addition reactions have the largest synthetic potential in fullerene chemistry. They also serve as a probe for screening the chemical properties of fullerene surfaces. 

Therefore, most additions to are exothermic reactions. The exofhermicity of subsequent additions decreases with an increasing number of addends already bound to CgQ. This holds also for the formation of T -complexes. For example, the addition of one Pt atom to releases 17 kcal moh of global strain energy, whereas 

The conjugated C-atoms of a fullerene respond to the deviation from planarity by rehybridization of the sp o and the p Jt orbitals, since pure p character of Jt orbitals is only possible in strictly planar situations ]56]. The electronic struchue of non-planar organic molecules has been analyzed by Haddon using the Jt orbital axis vector (POAV) analysis. For Cjq an average o bond hybridization of sp and a fractional s character of 0.085 (POAVl) or 0.081 (POAV2) was foimd ]59-63]. Consequently, the Jt orbitals extend further beyond the outer surface than into the interior of Cgg. This consideration implies, moreover, that fullerenes and, in particular, Cgg are fairly electronegative molecules [64, 65] since, due to the rehybridization, low-lying Jt orbitals also exhibit considerable s character. 

With incremental functionalization of the fullerene, the LUMO of the remaining conjugated framework is raised in energy. 

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Principles and Perspectives of Fullerene Chemistry The closed shell systems 20 (N=2),... 

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