Spin‐State Control in Dysprosium(III) Metallacrown Magnets via Thioacetal Modification

Abstract

Integrating controllable spin states into single‐molecule magnets (SMMs) enables precise manipulation of magnetic interactions at a molecular level, but remains a synthetic challenge. Herein, we developed a 3d‐4f metallacrown (MC) magnet [DyNi5(quinha)5(Clsal)2(py)8](ClO4)∙4H2O (H2quinha = quinaldichydroxamic acid, HClsal = 5‐chlorosalicylaldehyde) wherein a square planar NiII is stabilized by chemical stacking. Thioacetal modification was employed via post‐synthetic ligand substitutions and yielded [DyNi5(quinha)5(Clsaldt)2(py)8](ClO4)·3H2O (HClsaldt = 4‐chloro‐2‐(1,3‐dithiolan‐2‐yl)phenol). Thanks to the additional ligations of thioacetal onto the NiII site, coordination‐induced spin state switching (CISSS) took place with spin state altering from low‐spin S = 0 to high‐spin S = 1. The synergy of CISSS effect and magnetic interactions results in distinct energy splitting and magnetic dynamics. Magnetic studies indicate prominent enhancement of reversal barrier from 57 cm−1 to 423 cm−1, along with hysteresis opening and an over 200‐fold increment in coercive field at 2 K. Ab initio calculations provide deeper insights into the exchange models and rationalize the relaxation/tunnelling pathways. These results demonstrate here provide a fire‐new perspective in modulating the magnetization relaxation via the incorporation of controllable spin states and magnetic interactions facilitated by the CISSS approach.