SYNTHESIS AND ELECTROCHEMICAL INVESTIGATIONS OF MOLECULAR ARCHITECTURES INVOLVING C-60 AND TETRAPHENYLPORPHYRIN AS BUILDING-BLOCKS

A C-60-porphyrin diad 3a has been prepared by connecting a zinc porphy rin and C-60 via nucleophilic cyclopropanation, The fullerene diad as well as the related precursor porphyrins 1a, 2a have been investigated by cyclic and differential pulse voltammetry in dichloromethane. Wher eas no oxidation peaks were observed for C-60, all compounds 1a-3a exh ibit two successive, quasi-reversible oxidation peaks in terms of an E E mechanism. The peak potentials of all three species almost coincide, due to an oxidation of the porphyrin ring system in all cases. In the cathodic process, on the other hand, the compounds are reduced in qua si-reversible four (C-60), two (1a,2a) and five (3a) one-electron tran sfers. The first two formal potentials of 3a (resulting from the C-60 moiety) are shifted towards negative potentials by 40 mV, as compared to C-60, which is typical for methanofullerenes. Aside from coulombic effects, there is almost no electronic interaction between the C-60 an d porphyrin parts in 3a, Furthermore, a mixed hexaadduct 4 of C-60 wit h an octahedral addition pattern incorporating a zinc tetraphenylporph yrin has been synthesized.