An unprecedented [5,6]-open adduct via a direct benzyne-C60 cycloaddition

Cycloaddition is one of the best-studied types of reactions in the organic chemistry of fullerenes, engendering [6,6]-closed adducts in the vast majority of cases. Notwithstanding that a formation of open fulleroid structures is undoubtedly of theoretical interest, no one has demonstrated the conformation of [5,6]-open fulleroid via the direct cycloadditions. Here, we establish that cycloaddition between C60 and benzyne in situ generated from 2-amino-4,5-dibutoxybenzoic acid affords a new type of elusive [5,6]-open structure that is characterized on the basis of NMR, UV–vis spectroscopy, and cyclic voltammetry. Additionally, from density functional theory (DFT) calculations for possible [5,6]-open and [6,6]-closed adducts induced of benzyne-C60 reaction, as expected, features such as the charge distributions, binding characteristics, and frontier molecular orbital levels, are affected by the different binding modes in C60 cage.