Hydrazone-Based Lanthanide Single-Molecule Magnets

Abstract

To date, a great number of lanthanide SMMs have been reported through applying rigid mixed-donor hydrazone ligands which can be modified very easily by altering the hydrazide or aldehyde parts. This chapter first focuses on two typical polynuclear Dy complexes which greatly contribute to the elu-cidation of two-step relaxation model and are subsequently devoted to the constructions of lanthanide SMMs based on the different hydrazide parts and their magnetic analysis. Therefore, the assembly of hydrazone ligands with lanthanide salts under different conditions turns out to be an effective way to discover new lanthanide SMMs and to explore the origin of complicated magnetic dynamics. Keywords Hydrazone ligands · Two-step relaxation · Keto-enol tautomerism · Hula hoop · Magnetic exchange As seen in the third and fourth chapters, Schiff base ligands exhibit some advantages over other ligands in the assembly of polynuclear lanthanide SMMs. Generally speaking, such ligands incorporate a great number of coordinating donors such as N and O atoms with an affinity for lanthanide ions, thus leading to the polytopic coordination within a single ligand. More importantly, such donors are usually coupled into multiple dentate coordination pockets preferring chelating a single lanthanide center, which is favorable to self-assembly of lanthanide clusters. As a special class in Schiff base ligands, hydrazone ligands exhibit not only the common features of Schiff base ligands but also some special coordination characteristics, which have proven to be beneficial to achieve high-performance lanthanide SMMs. Therefore, considerable lanthanide SMMs have been obtained using hydrazone ligands which seem to be in great abundance and variety due to the various alternations of hydrazide and aldehyde reagents, as seen in Fig. 5.1.