Unravelling Magneto-Structural Correlations in Pseudo D_5h/6h-Symmetric Dy(III) Single-Molecule Magnets

Recent breakthroughs in Dy^III-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 (T_B). 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-D_5h and D_6h Dy^III 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 (U_cal > 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 Dy^III SMMs in pseudo- pseudo-D_5h and D_6h geometries, laying the groundwork for the next generation of air-stable, high-blocking-temperature SMMs.