Energy-Barrier Enhancement by Ligand Substitution in Tetrairon(III) Single-Molecule Magnets

摘要

The tailoring of the structure and properties of single-molecule magnets (SMMs) is a very active branch of modern coordination chemistry. Investigations on classes of structurally related SMMs, such as those of the Mn_(12) family, have helped unravel the mechanisms underlying slow magnetic relaxation in high-spin molecules, a key step in both fundamental and application-oriented research. At the same time, the search for new SMMs with higher blocking temperatures has fueled synthetic efforts aimed, on one side, at increasing structural control on cluster architectures and, on the other side, at developing the so-called serendipitous-assembly approach. An elegant strategy for structural design is based on site-specific modification of preformed clusters. Carboxylate abstraction from Mn_(12) clusters, for instance, has been carried out site specifically using a variety of incoming ligands, such as nitrates, phosphanates, phosphates, or different carboxylates. However, these substitutions are accompanied by only small perturbation of the magnetic properties.