Bidirectional Electron Transfer Capability in Phthalocyanine–Sc₃N@I_h–C₈₀ Complexes

To activate oxidative and/or reductive electron transfer reactions, N-pyridyl-substituted Sc₃N@I_h–C₈₀ (4) and C₆₀ (3) fulleropyrrolidines have been prepared and axially coordinated to electron-rich (1) or electron-deficient (2) Zn­(II)­phthalocyanines (Zn­(II)­Pcs) through zinc-pyridyl, metal–ligand coordination affording a full-fledged family of electron donor–acceptor ensembles. An arsenal of photophysical assays as they were carried out with, for example, 1/4 and 2/4 show unambiguously that a Zn­(II)­Pc-to-Sc₃N@I_h–C₈₀ photoinduced electron transfer takes place in the former ensemble, whereas a Sc₃N@I_h–C₈₀-to-Zn­(II)­Pc electron transfer occurs in the latter ensemble. To the best of our knowledge, this is the first time that a fullerene-based molecular building block shows an electron transfer dichotomy, namely acting both as electron-acceptor or electron-donor, and its outcome is simply governed by the electronic nature of its counterpart. In light of the latter, the present work, which involves the use of Sc₃N@I_h–C₈₀, one of the most abundant and easy-to-purify endohedral metallofullerenes, is, on one hand, a paradigmatic change and, on the other hand, an important milestone en-route toward the construction of easy-to-prepare molecular materials featuring switchable electron transfer reactivity.