Regulating the electronic and spin structure of endohedral metallofullerenes: a case investigation of ScN@C and ScC@C.

The electrochemical and paramagnetic properties of endohedral metallofullerenes (EMFs) have drawn extensive attention due to their huge potential in the fields of molecular devices, biomedicines, quantum information processing, . Exohedral modification of the fullerene carbon cage, such as in the classical Prato reaction, is an effective and facile approach to regulate the electronic structure and molecular dynamics of EMFs. In this work, novel pyrrolidine products of ScN@C and ScC@C were successfully synthesized Prato reactions using L-cysteine and paraformaldehyde. Structure characterizations demonstrated that two regioisomers with a [5,6] and a [6,6] cycloaddition on the -C cage were obtained both for ScN@C and ScC@C. Besides, the [6,6]-monoadduct of ScN@C was thermally stable while the [5,6]-monoadduct exhibited a retro-cycloaddition ability to recover the pristine ScN@C. Electrochemical measurements revealed that the redox potential of ScN@C could be tuned such exohedral modifications. Furthermore, the paramagnetic property and internal dynamics of the encapsulated ScC cluster of ScC@C can be well-regulated by controlling the spin density of the molecule. The present work could provide a new approach to regulate the electronic and/or spin structure of EMFs.