Chemical Reactivity and Addition Pattern on C60 and C70

Abstract

Fullerenes are a class of three-dimensional all-carbon hollow molecules incorporating conjugated π systems. The important principle to determine the stability of fullerene cages is the isolated pentagon rule (IPR). The chemical reactivity of fullerenes is similar to that of a fairly localized, electron-deficient polyolefin. Chemical modification of fullerenes is generally classified into exohedral modification and skeletal modification. Exohedral modification affords fullerene derivatives with one or several addends covalently linked to the spherical carbon framework. The main reactions are cycloadditions, radical additions, and nucleophilic additions. Skeletal modification produces open-cage fullerenes or heterofullerenes. Open-cage fullerenes usually refer to fullerene derivatives with more than one σ-bond scission and significantly disturbed π system. Heterofullerenes are those in which one or more carbons are replaced by other non-carbon atoms such as nitrogen. The addition pattern of exohedral modification on fullerenes is generally divided into monoaddition and multiaddition. In the case of monoaddition, C60 has only two possible isomers, including 1, 2- and 1, 4-additions, but for C70, there are eight possible isomers, including the predominant 1, 2- and 5, 6-additions. As for multiaddition, low regioselectivity is generally observed and complex regioisomers are easily formed. Fullerene derivatives have displayed promising applications in many fields including material science, biological medicine, and nanotechnology due to their outstanding properties.