Lithium(I)-Incorporated Tetranuclear Dysprosium(III) Complexes with Single-Molecule Magnetic and Luminous Properties

Abstract

Despite extensive research on dysprosium-based single-molecule magnets (SMMs), the deliberate incorporation of alkali-metal ions, such as lithium, as structure-directing components remains relatively unexplored. Herein, the reaction of an electron-rich lithiated Schiff-base ligand with DyCl3 afforded tetranuclear heterometallic Li–Dy complexes featuring three types of E-bridging anions (E = ClO4–, CO32–, C2O42–). Single-crystal X-ray diffraction analysis revealed distorted square-antiprismatic DyIII centers with N2O6 coordination environments and intramolecular Dy···Dy distances ranging from 3.58 to 3.94 Å. Magnetic investigations, supported by ab initio calculations, indicated weak antiferromagnetic (AFM) interactions between DyIII centers. All complexes exhibit zero-field single-molecule magnet (SMM) behavior, with low-temperature relaxation governed by quantum tunneling/direct processes and higher temperature relaxation involving Raman and Orbach mechanisms. The effective energy barriers for magnetization reversal (Ueff) range from 19 to 37 K. In addition, the complexes exhibit ligand-based green/yellow fluorescence, demonstrating the coexistence of SMM behavior and visible region emission in the heterometallic Li–Dy molecular framework.