Since the discovery of C60 in 1985 , fullerenes have attracted the attention of chemists due to their unique structure, properties and reactivity, along with their potential applications in a variety of fields ranging from materials science to biomedicine. The preparation of cyclohexadiene-fused C60 derivatives can be achieved by [2+2+2] cycloaddition reactions of C60 with alkynes. This particular class of fullerene derivatives is interesting from the synthetic point of view because they can be converted into the corresponding open-cage bis(fulleroids) when subjected to photochemical conditions. Based on our previous theoretical DFT study that showed the viability of a rhodium-catalyzed [2+2+2] cycloaddition reaction of two alkynes and C60, here we report the first example of [2+2+2] cycloaddition involving C60 and diynes under catalytic conditions promoted by a rhodium(I) catalyst, which leads to the formation of a series of bis(fulleroids). The process takes place in a single step, with no photoexcitation required. The process mechanism has been studied by means of DFT calculations, proving that the cyclohexadiene-fused intermediate resulting from a [2+2+2] cycloaddition evolves into the final product through a Rh-catalyzed di-π-methane rearrangement. Further functionalization of the reaction products has also been achieved by Suzuki-Miyaura cross-coupling reaction and oxidative ring expansion. Finally, the electrochemical behavior of the products synthesized has been studied, as well as their performance as electron transporting materials (ETMs) in perovskite solar cells (PSCs).

Preparation of open-cage fullerene derivatives by rhodium(I)-catalyzed [2+2+2] cycloaddition of diynes and C60: An experimental and theoretical study

256th National Meeting (2018)

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