January 29, 2024 | Jack Emerson-King, Gemma K. Gransbury, George F. S. Whitehead, Iñigo J. Vitorica-Yrezabal, Mathieu Rouzières, Rodolphe Clérac, Nicholas F. Chilton, David P. Mills
This study reports the synthesis and characterization of a bent dysprosium bis(amide) complex, $[\mathrm{Dy}\{\mathrm{N}(\mathrm{Si}^{\prime} \mathrm{Pr}_{3})_{2}\}_{2}]^{+}$, and its diamagnetic yttrium analogue. The complex was prepared through a series of synthetic steps, including the formation of intermediate mononuclear complexes and their subsequent coupling. The solid-state structure of the dysprosium complex was determined by X-ray crystallography, revealing a bent geometry with a significant deviation from linearity. Magnetic measurements showed that the complex exhibits relatively low-lying and highly mixed excited states, with a measured effective magnetic anisotropy energy barrier ($U_{\text{eff}}$) of 950 ± 30 K, which is lower than the predicted value based on idealized linear two-coordinate dysprosium complexes. Ab initio calculations supported these findings, indicating that the flexible coordination environment and multiple close Dy…H–C–C–Si contacts in the complex contribute to rapid magnetic relaxation. The study highlights the importance of molecular geometry and ligand flexibility in controlling the magnetic properties of single-molecule magnets (SMMs), particularly in achieving high blocking temperatures.This study reports the synthesis and characterization of a bent dysprosium bis(amide) complex, $[\mathrm{Dy}\{\mathrm{N}(\mathrm{Si}^{\prime} \mathrm{Pr}_{3})_{2}\}_{2}]^{+}$, and its diamagnetic yttrium analogue. The complex was prepared through a series of synthetic steps, including the formation of intermediate mononuclear complexes and their subsequent coupling. The solid-state structure of the dysprosium complex was determined by X-ray crystallography, revealing a bent geometry with a significant deviation from linearity. Magnetic measurements showed that the complex exhibits relatively low-lying and highly mixed excited states, with a measured effective magnetic anisotropy energy barrier ($U_{\text{eff}}$) of 950 ± 30 K, which is lower than the predicted value based on idealized linear two-coordinate dysprosium complexes. Ab initio calculations supported these findings, indicating that the flexible coordination environment and multiple close Dy…H–C–C–Si contacts in the complex contribute to rapid magnetic relaxation. The study highlights the importance of molecular geometry and ligand flexibility in controlling the magnetic properties of single-molecule magnets (SMMs), particularly in achieving high blocking temperatures.