Unravelling Magneto-Structural Correlations in Pseudo D 5 h /6 h -Symmetric Dy(III) Single-Molecule Magnets

Recent breakthroughs in DyIII-based single-molecule magnets (SMMs), including magnetic hysteresis at liquid nitrogen temperatures, have significantly advanced their potential for real-world applications. However, challenges persist, especially in achieving precise geometric control over magnetic anisotropy and developing air-stable SMMs with higher blocking temperatures (TB). While ab initio multireference methods such as CASSCF/RASSI-SO have provided valuable insights into individual systems, these findings are often system-specific and difficult to generalize. In this work, we address this limitation by combining DFT and ab initio CASSCF/RASSI-SO calculations with systematic correlation analysis across a diverse set of pseudo-D5h and D6h DyIII complexes. These systems incorporate a variety of axial ligands (F⁻, t-BuO⁻, MeOH, Cp⁻, OCNH₂, corannulene) and equatorial donors (nitrogen/oxygen/sulfur-donor 15-crown-5 and 18-crown-6), including mixed-ligand architectures. Our analysis uncovers strong trends linking high energy barriers (Ucal > 1200 cm⁻¹) to three key geometric factors: minimal Dy displacement (<0.1 Å) from the equatorial plane, low angular distortion (<2°), and a high axial ratio (>0.90). These correlations, observed across multiple complexes, provide a set of generalizable design principles for engineering high-performance DyIII SMMs in pseudo- pseudo-D5h and D6h geometries, laying the groundwork for the next generation of air-stable, high-blocking-temperature SMMs.