Optimization of Single‐Molecule Magnets by Suppression of Quantum Tunneling of the Magnetization
Jan Oldengott, Jürgen Schnack, Thorsten Glaser
Abstract
The ligand system triplesalen was rationally designed following requirements for polynuclear 3d single‐molecule magnets (SMMs). The essential central part is the C 3 symmetric, meta ‐phenylene bridging unit phloroglucinol for ferromagnetic interactions via the spin‐polarization mechanism. The triplesalen‐based [Mn III 6 Cr III ] 3+ SMMs strongly suppress the quantum tunneling of the magnetization (QTM) but exhibit blocking temperatures not exceeding 2 K. We have analyzed the reason for this behavior and found that the triplesalen ligands are not in the anticipated aromatic phloroglucinol form but in a non‐aromatic heteroradialene form. Here we present our strategies to optimize the triplesalen ligand system to suppress the heteroradialene formation and to enforce ferromagnetic interactions. This allowed us to study in detail the influence of exchange coupling on the QTM and relaxation properties of SMMs and provides valuable insights for further rational improvements of our triplesalen ligand system and of SMMs in general.