Gold Clusters With Open-Shell Ligands: Superatom Mediated Magnetic Interaction

Understanding the magnetic interactions within gold clusters that involve superatomic orbitals is critically important in advancing the development of nanoscale materials with magnetic functionality. In this study, we report on the synthesis of Ir-doped Au₁₂ (Ir@Au₁₂) icosahedral clusters functionalized with two open-shell verdazyl radicals at opposite poles, along with an investigation into their electronic, magnetic, and photophysical properties. The photoluminescence from the Ir@Au₁₂ cluster core is drastically quenched by the introduction of verdazyl ligands. The ultrafast time-resolved absorption spectroscopy reveals the electron transfer from the Ir@Au₁₂ core in the triplet excited state to the verdazyl ligand. The EPR study discloses the hyperfine coupling with the Au and Ir nuclei, indicating the spin density of the verdazyl radical moderately delocalized over the Ir@Au₁₂ core. These results provide direct evidence of electronic interaction between the organic radicals and Ir@Au₁₂ superatomic core. Furthermore, the variable temperature EPR study suggests weak magnetic communication between the two verdazyl radical ligands mediated by the Ir@Au₁₂ superatomic core. These findings will establish superatom-organic radical hybrids as a new class of multi-spin systems and provide a design strategy for photofunctional and magnetic nanomaterials based on atomically precise metal clusters.