Location
recognition at the molecular scale provides valuable information
about the nature of functional molecular materials. This study presents
a novel location sensing approach based on an endohedral metallofullerene,
Ce@C82, using its anisotropic magnetic properties, which
lead to temperature-dependent paramagnetic shifts in 1H
NMR spectra. Five site-isomers of Ce@C82CH2-3,5-C6H3Me2 were synthesized to demonstrate
the spatial sensing ability of Ce@C82. Single-crystal structures,
absorption spectra, and density functional theory calculations were
used to select the plausible addition positions in the radical coupling
reaction, which preferentially happens on the carbon atoms with high
electron density of the singly occupied molecular orbital (SOMO) and
positive charge. Temperature-dependent NMR measurements demonstrated
unique paramagnetic shifts of the 1H peaks, which were
derived from the anisotropic magnetism of the f-electron in the Ce
atom of the isomers. It was found that the magnetic anisotropy axes
can be easily predicted by theoretical calculations using the Gaussian
09 package. Further analysis revealed that the temperature-dependent
trend in the shifts is clearly predictable from the distance and relative
position of the proton from the Ce atom. Hence, the Ce-encapsulated
metallofullerene Ce@C82 can provide spatial location information
about nearby atoms through the temperature-dependent paramagnetic
shifts of its NMR signals. It can act as a molecular probe for location
sensing by utilizing the anisotropic magnetism of the encapsulated
Ce atom. The potentially low toxicity and stability of the endohedral
fullerene would make Ce@C82 suitable for applications in
biology and material science.