Magnetic endohedral metallofullerenes with floppy interiors

It is shown that ${\mathrm{Gd}}_{3}\mathrm{N}@{\mathrm{C}}_{80}$ is a highly magnetic and very stable motif that allows enhanced contrast magnetic resonance imaging and electric dipole moment with potential for cancer treatment. Using a synergistic approach combining Stern-Gerlach experiments in beams and first-principles electronic structure studies, it is demonstrated that an isolated ${\mathrm{Gd}}_{3}\mathrm{N}$ has a ground state spin moment of $23{\ensuremath{\mu}}_{B}$ followed by a noncollinear state of $17.2{\ensuremath{\mu}}_{B}$ only $88\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ above the ground state. The large moment is largely due to localized $f$ electrons. As a ${\mathrm{Gd}}_{3}\mathrm{N}$ is embedded inside a ${\mathrm{C}}_{80}$ cage, the localized $f$ electrons maintain the magnetic character while the hybridization between the $s$, $d$ states of isolated ${\mathrm{Gd}}_{3}\mathrm{N}$ and $p$ states of ${\mathrm{C}}_{80}$ leads to a strongly bound motif with an interaction energy of $13.63\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and a large highest-occupied-molecular-orbital\char21{}lowest-unoccupied-molecular-orbital gap of $1.48\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. ${\mathrm{Gd}}_{3}\mathrm{N}@{\mathrm{C}}_{80}$ is further shown to possess two isomers corresponding to the location of the N atom on either side of the ${\mathrm{Gd}}_{3}$ triangle with an appreciable electric dipole moment and a low barrier of $91\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ for transition between them offering potential for a fluctuating dipole.