Light-Controlled Regioselective Synthesis of Fullerene Bis-Adducts

Multi-functionalization and isomer-purity of fullerenes are crucial tasks for the development of fullerene chemistry in various fields. In both current main approaches - tether-directed covalent functionalization and supramolecular masks - the control of regioselectivity requires multi-step synthetic procedures to prepare the desired tether or mask. Herein, we describe light-responsive tethers, containing an azobenzene photoswitch and two malonate groups, in the double cyclopropanation of [60]fullerene. The formation of the bis-adducts and their spectroscopic and photochemical properties, as well as the effect of azobenzene photoswitching on the regiochemistry of the bis-addition, have been studied. The behavior of the tethers depends on the geometry of the connection between the photoactive core and the malonate moieties. One tether lead to strikingly different adduct distribution for the E and Z isomers, indicating that the covalent bis-functionalization of C60 can be controlled by light.