From polynuclear lanthanide molecular magnets to 3d-4f magnetoelectric architectures: Towards room-temperature giant magnetoelectric coupling

Single-molecule magnets (SMMs) built from 4f and 3d-4f coordination architectures offer a unique platform for engineering magnetic anisotropy through molecular, rather than lattice-level, design. Using a pyridine-based Schiff base ligand, (E)-2-((pyridin-2-ylmethylene)amino)phenol, we synthesized a family of phenoxo-bridged Dy$_2$ dimers with $\beta$-diketonate co-ligands, revealing intramolecular antiferromagnetic coupling and effective relaxation barriers ($\Delta E/k_\mathrm{B}$) up to 25.65 K, tunable by systematically varying single-ion anisotropy across the series. Extending this design to heterodinuclear Zn$^\mathrm{II}$-Ln$^\mathrm{III}$ complexes, we demonstrate that diamagnetic Zn$^\mathrm{II}$ substitution suppresses quantum tunneling of magnetization, enhancing field-induced SMM behavior in the Dy$^\mathrm{III}$ analogue to an effective barrier of 155 K among the notable values reported for this ligand class.

Beyond static magnetism, these soft, chirality-amenable molecular scaffolds present a compelling opportunity to address a longstanding challenge: room-temperature magnetoelectric (ME) coupling. Unlike inorganic ME systems, where ferroelectricity and magnetism are intrinsically incompatible, molecular polarization arising from reorientation and structural distortion is inherently couple to spin. We outline a predictive framework integrating chirality-driven symmetry breaking, supramolecular control of dipole alignment, and multireference computational treatment of spin-orbit and correlation effects to translate our anisotropic 3d-4f building blocks into quantitatively engineered, device-relevant molecular magnetoelectric.