Linear hexanuclear helical dysprosium single-molecule magnets: the effect of axial substitution on magnetic interactions and relaxation dynamics

• Published in: Dalton transactions : an international journal of inorganic chemistry 2019-09, Vol.48 (37), p.1462-1468
• Main Authors: Lu, Jingjing, Li, Xiao-Lei, Zhu, Zhenhua, Liu, Shuting, Yang, Qianqian, Tang, Jinkui
• Format: Article
• Language: English
• Subjects: Crystallography; Dysprosium; Ferromagnetism; Imines; Ligands; Magnetic induction; Magnetic properties; Magnetic relaxation; Magnets; Substitution reactions
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c9dt03101d

The reaction between the rigid Schiff-base ligand H 4 L ([3,6-bis(2-hydroxy-3-methoxybenzylidene)hydrazinecarbonyl]-pyridazine) and different dysprosium( iii ) salts afforded two new linear hexanuclear helical clusters, [Dy 6 L 3 (SCN) 6 (DMF) 8 ]·4DMF ( 1 ), and [Dy 6 L 3 (NO 3 ) 6 (DMF) 4 (H 2 O) 2 ]·8DMF ( 2 ), which possess a similar Dy 6 core with [Dy 6 L 3 (PhCOO) 6 (CH 3 OH) 6 ]·11CH 3 OH·H 2 O ( 3 ). Modulation of the axial ligands around Dy III sites causes different coordination geometries and magnetic interactions, resulting in distinct magnetic relaxation behaviors. Compounds 1 and 2 show typical single-molecule magnet (SMM) properties with effective barriers ( U eff ) of 15 and 68 K, respectively, which could greatly profit from strong ferromagnetic interactions compared with compound 3 . Presence of a hula-hoop-like geometry of the Dy III ions and stronger ferromagnetic interactions results in better SMM performance of compound 2 than that of 1 . Structural modification of the Dy 6 cores of [Dy 6 L 3 (SCN) 6 (DMF) 8 ]·4DMF ( 1 ) and [Dy 6 L 3 (NO 3 ) 6 (DMF) 4 (H 2 O) 2 ]·8DMF ( 2 ) results in the transition of magnetic relaxation behavior from single relaxation to multiple relaxation.