Energy level tunable pre-click functionalization of [60]fullerene for nonlinear optics

[2+2] click chemistry followed by Prato reaction is reported the first time for energy level tunable functionalization of C₆₀. The novel kind of D–A–A C₆₀ charge-transfer complexes exhibits strikingly enhanced optoelectronic properties and significant third-order nonlinear optical potentials. Meanwhile, structures of the ‘click’ C₆₀ products were fully characterized by NMR, IR, and MS. By introducing TCNE, TCNQ, F₄-TCNQ click monomers, we obtained energy level tunable fullerene derivatives in high solubility, which was beneficial for processing. Furthermore, UV–vis spectra were enlarged with end-absorptions into the near infrared region, indicating excellent nonlinear optical properties. The electrochemical properties have been studied by cyclic voltammograms, which were in good correlation with the optical spectroscopic and DFT data.