Anion-Templated Assembly and Magnetocaloric Properties of a Nanoscale {Gd38} Cage versus a {Gd48} Barrel.

The comprehensive study reported herein provides compelling evidence that anion templates are the main driving force in the formation of two novel nanoscale lanthanide hydroxide clusters, {Gd₃₈(ClO₄)₆} ( 1) and {Gd₄₈Cl₂(NO₃)} ( 2), characterized by single-crystal X-ray crystallography, infrared spectroscopy, and magnetic measurements. {Gd₃₈(ClO₄)₆}, encapsulating six ClO₄⁻ ions, features a cage core composed of twelve vertex-sharing {Gd₄} tetrahedrons and one Gd⋅⋅⋅Gd pillar. When Cl⁻ and NO₃⁻ were incorporated in the reaction instead of ClO₄⁻, {Gd₄₈Cl₂(NO₃)} is obtained with a barrel shape constituted by twelve vertex-sharing {Gd₄} tetrahedrons and six {Gd₅} pyramids. What is more, the cage-like {Gd₃₈} can be dynamically converted into the barrel-shaped {Gd₄₈} upon Cl⁻ and NO₃⁻ stimulus. To our knowledge, it is the first time that the linear M-O-M′ fashion and the unique μ₈-ClO₄⁻ mode have been crystallized in pure lanthanide complex, and complex 2 represents the largest gadolinium cluster. Both of the complexes display large magnetocaloric effect in units of J kg⁻¹ K⁻¹ and mJ cm⁻³ K⁻¹ on account of the weak antiferromagnetic exchange, the high N_Gd/ M_W ratio (magnetic density), and the relatively compact crystal lattice (mass density). [ABSTRACT FROM AUTHOR]