Functionalization of Endohedral Metallofullerenes toward Improving Barrier Height for the Relaxation of Magnetization for Dy2@C80-X (X = CF3, C3N3Ph2).

We theoretically studied the electronic and magnetic properties of the exterior functionalized endohedral metallofullerenes (EMFs) of Gd2@ I h-C80-X (where X is the exterior functional group). Molecular orbital analysis suggests that the presence of unpaired electron on the I h-C80 cage is not favoring the observation of stable species. One of the effective strategies to address this problem is by attaching an exterior functional group to the fullerene cage. Out of the studied exterior functionalized EMFs, we were successful in finding two stable species such as Gd2@ I h-C80-CF3 and Gd2@ I h-C80-C3N3Ph2 with no unpaired spin on the cage. Further, we utilized exterior functional groups such as -CF3 (1) and -C3N3Ph2 (2) to model and to stabilize dinuclear Dy2@ I h-C80 species, and we thoroughly investigated their magnetic properties using ab initio calculations. Within the single-ion paradigm, DyIII ions in 1 and 2 are magnetically anisotropic, and their magnetization-reversal energy barriers are estimated to be ∼698 and ∼705 cm-1, respectively. Furthermore, beyond the single-ion paradigm, i.e., considering a ferromagnetic coupling (∼30 cm-1) between the lanthanide ions and the radical spin, the energy barriers of 1 and 2 are estimated to be 79.8 and 73.0 cm-1, respectively.