Guest-Assisted Assembled Hydrogen-Bonded Organic Frameworks of Dysprosium Single-Ion Magnets

Abstract

Lanthanide single-ion magnets (Ln-SIMs) have gradually emerged as one of the important candidates for next-generation magnetic materials. However, improving the environmental stability of Ln-SIMs remains one of the key challenges. Herein, we present a strategy for preparing highly thermostable Ln-SIMs through guest-assisted assembly of Ln-SIM-based hydrogen bonded organic frameworks (HOFs). Two HOFs based on Ln-SIMs, [HGdn]2[Dy(dpa)2(Hdpa)]·0.5Gdn·H2O (HOF-1) and [Dy(Hdpa)3]2·3H2O (HOF-2), have been prepared, where Gdn and H2dpa represent guanidine and pyridine-2,6-dicarboxylic acid, respectively. HOF-1 is constructed from [Dy(dpa)2(Hdpa)]2- anions and [HGdn]+ cations, giving rise to a three-dimensional HOF structure. HOF-2 consists of [Dy(Hdpa)3] units linked by guest H2O molecules to form a two-dimensional HOF. Both HOF-1 and HOF-2 exhibit excellent thermal stability. They can maintain their frameworks above 290 °C and thus rank among the most thermally stable Ln-SIMs reported to date. They also exhibit field-induced dual magnetic relaxation behaviors, with the highest effective energy barriers (Ueff) of 61.4 K (HOF-1) and 61.5 K (HOF-2), respectively. This work presents a novel approach for enhancing the structural stability of Ln-SIMs and regulating their magnetic properties through a guest-assisted assembly strategy for supramolecular HOF structures.