Organometallic Lanthanide Single-Molecule Magnets

Molecules that possess an energy barrier to spin inversion have intriguing potential<br/>applications in areas such as magnetic refrigeration, molecular spintronics and high-density information<br/>storage. For these applications, however, key performance characteristics such as large spin-relaxation<br/>barriers and high magnetic blocking temperatures are required. Lanthanides have been proven to be<br/>particularly well-suited for the design of single-molecule magnets owing to their large magnetic moments and<br/>magnetic anisotropy that stem from strong spin-orbit coupling of the 4f orbitals. By using lanthanide ions such<br/>as Tb , Dy , and Er which possess intrinsically large orbital angular momentum, significantly higher<br/>barriers and blocking temperatures can be achieved. A general methodology to enhance single-molecule<br/>magnet properties in mononuclear lanthanide complexes comprises matching the ligand field symmetry with<br/>the anisotropic electron density distribution of the maximal M state. Employing this methodology, the synthesis<br/>of mononuclear rare earth metallocene complexes that function as new lanthanide-based single-molecule<br/>magnets will be presented. Another particularly successful strategy towards improving magnetic blocking<br/>temperatures is to generate strong magnetic exchange between lanthanide centers through the employment of<br/>radical bridging ligands. If the magnetic exchange coupling is large enough then quantum tunneling of the<br/>magnetization can be suppressed. Here, the synthesis of several radical-bridged lanthanide single-molecule<br/>magnets will be presented and effective suppression of quantum tunneling pathways using various organic<br/>bridging radical ligands will be demonstrated. A special emphasis will be on the importance of expanding the<br/>organometallic chemistry of the lanthanide ions as one successful way to new single-molecule magnets.