Supermolecular Aggregates of Mononuclear and Asymmetric Dinuclear Dysprosium Single-Molecule Magnets Assembled by Intermolecular Hydrogen Bonds

Abstract

By manipulating the aggregate states of dysprosium singlemolecule magnets (Dy III -SMMs), the hydrogen bonds have played key roles in realizing aggregation-induced suppression of quantum tunneling of magnetization (QTM), thus becoming a new tool to optimize the performance of Dy III -SMMs. Yet, supermolecular aggregates of Dy III -SMMs assembled by hydrogen bonds are still scarcely reported so far. Herein, two such aggregates, [Dy(H 3 spho)-, were prepared by N,N′-bis-(salicylicdene)pyridine-2,6-dicarbohydrazide N-oxide (H 4 spho) and N,N′-bis(5chlorosalicylicdene) pyridine-2,6-dicarbohydrazide N-oxide (H 4 cspho), respectively. SAH-1 shows a supermolecular dimer structure, where two mononuclear molecules are linked together by hydrogen bonds and arranged in a side-by-side fashion. SAH-2 is a three-dimensional (3D) hydrogen-bonded organic framework (HOF). Its molecule features an asymmetric dinuclear {Dy 2 } structure based on a single symmetric ligand, which has not been observed in the whole lanthanide complex family. Both SAH-1 and SAH-2 exhibit desirable SMM behavior, with the highest effective energy barrier (U eff ) of 67(2) and 62(3) K, respectively. SAH-2 also displays field-induced dual-relaxation behavior. The magnetic dilution experiments reveal that the dipole interactions relating to supermolecular aggregate states have non-negligible effects on the relaxation of SAH-1 and SAH-2.