Self-assembly of rare octanuclear quad(double-stranded) cluster helicates showing slow magnetic relaxation and the magnetocaloric effect

Four rare quad(double-strand) cluster helicates containing Ln8 polyhedron cores, namely [Ln 8 (HL) 4 L 4 (OH) 6 (H 2 O) 2 (acac) 2 ](ClO 4 ) 4 ·2CH 3 OH·12H 2 O (Ln = Gd for 1 , Tb for 2 , Dy for 3 , and Ho for 4 , respectively), have been assembled by using lanthanide salts and flexible ligands of...

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Bibliographic Details
Published in:New journal of chemistry 2018, Vol.42 (21), p.17652-17658
Main Authors: Yao, Min-Xia, Cai, Li-Zheng, Deng, Xiao-Wei, Zhang, Wei, Liu, Sui-Jun, Cai, Xu-Min
Format: Article
Language:English
Subjects:
Aminophenol
Antiferromagnetism
Clusters
Couplings
Crystallography
Cubane
Gadolinium
Ligands
Magnetic induction
Magnetic permeability
Magnetic properties
Magnetic relaxation
Magnetism
Polyhedra
Self-assembly
Structural analysis
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Summary:Four rare quad(double-strand) cluster helicates containing Ln8 polyhedron cores, namely [Ln 8 (HL) 4 L 4 (OH) 6 (H 2 O) 2 (acac) 2 ](ClO 4 ) 4 ·2CH 3 OH·12H 2 O (Ln = Gd for 1 , Tb for 2 , Dy for 3 , and Ho for 4 , respectively), have been assembled by using lanthanide salts and flexible ligands of H 2 L obtained from a 1 : 2 condensation reaction between 1,1′-(2,6-pyridyl)bis-1,3-butanedione and 2-aminophenol. In each complex, four pairs of organic ligands (HL − and L 2− ) wrap the Ln8 polyhedron presenting a bicapped face-sharing double cubane configuration in a propeller-like form, resulting in the formation of octanuclear quad(double-stranded) helicates by coordination interactions of Ln–O/N bonds. The dc magnetic susceptibility measurements of complex 1 suggested the existence of weak antiferromagnetic couplings between neighboring Gd III ions and the magnetocaloric effect with −Δ S maxm = 22.9 J kg −1 K −1 at 3.5 K for Δ H = 7 T. Ac magnetic susceptibility measurements of complex 3 at zero dc field demonstrated a slow magnetic relaxation behavior below 8.0 K with an effective energy barrier of 2.14 K.
ISSN:1144-0546
1369-9261
DOI:10.1039/C8NJ04169E