Anion-Templated Assembly and Magnetocaloric Properties of a Nanoscale {Gd_(38)} Cage versus a {Gd_(48)} Barrel

摘要

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, {Gd_(38)(C1O_4)_6} (1) and {Gd_(48)Cl2(N03)} (2), characterized by single-crystal X-ray crystallography, infrared spectroscopy, and magnetic measurements. {Gd_(38)(C1O_4)_6}, encapsulating six C1O_4~- ions, features a cage core composed of twelve vertex-sharing {Gd4} tetrahedrons and one Gd…Gd pillar. When Cl~- and NO_3~- were incorporated in the reaction instead of ClO_4~-, {Gd_(48)Cl_2(NO_3)} is obtained with a barrel shape constituted by twelve vertex-sharing {Gd4} tetrahedrons and six {Gd_5} pyramids. What is more, the cage-like {Gd_(38)} can be dynamically converted into the barrel-shaped {Gd_(48)} upon Cl-- and NO_3~- stimulus. To our knowledge, it is the first time that the linear M-O-M' fashion and the unique μ_8-ClO_4~- 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 Jkg~(-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).