Functionalization of Endohedral Metallofullerenes toward Improving Barrier Height for the Relaxation of Magnetization for Dy@C-X (X = CF, CNPh).

We theoretically studied the electronic and magnetic properties of the exterior functionalized endohedral metallofullerenes (EMFs) of Gd@ I -C-X (where X is the exterior functional group). Molecular orbital analysis suggests that the presence of unpaired electron on the I -C 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 Gd@ I -C-CF and Gd@ I -C-CNPh with no unpaired spin on the cage. Further, we utilized exterior functional groups such as -CF (1) and -CNPh (2) to model and to stabilize dinuclear Dy@ I -C species, and we thoroughly investigated their magnetic properties using ab initio calculations. Within the single-ion paradigm, Dy ions in 1 and 2 are magnetically anisotropic, and their magnetization-reversal energy barriers are estimated to be ∼698 and ∼705 cm, respectively. Furthermore, beyond the single-ion paradigm, i.e., considering a ferromagnetic coupling (∼30 cm) 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, respectively.