# Co–Ln Mixed-Metal Phosphonate Grids and Cages as Molecular Magnetic Refrigerants

dataset

posted on 22.02.2016, 08:22 by Yan-Zhen Zheng, Marco Evangelisti, Floriana Tuna, Richard E. P. WinpennyThe synthesis, structures, and magnetic properties of
six families
of cobalt–lanthanide mixed-metal phosphonate complexes are
reported in this Article. These six families can be divided into two
structural types: grids, where the metal centers lie in a single plane,
and cages. The grids include [4 × 3] {Co

_{8}Ln_{4}}, [3 × 3] {Co_{4}Ln_{6}}, and [2 × 2] {Co_{4}Ln_{2}} families and a [4 × 4] {Co_{8}Ln_{8}} family where the central 2 × 2 square is rotated with respect to the external square. The cages include {Co_{6}Ln_{8}} and {Co_{8}Ln_{2}} families. Magnetic studies have been performed for these compounds, and for each family, the maximum magnetocaloric effect (MCE) has been observed for the Ln = Gd derivative, with a smaller MCE for the compounds containing magnetically anisotropic 4f-ions. The resulting entropy changes of the gadolinium derivatives are (for 3 K and 7 T) 11.8 J kg^{–1}K^{–1}for {Co_{8}Gd_{2}}; 20.0 J kg^{–1}K^{–1}for {Co_{4}Gd_{2}}; 21.1 J kg^{–1}K^{–1}for {Co_{8}Gd_{4}}; 21.4 J kg^{–1}K^{–1}for {Co_{8}Gd_{8}}; 23.6 J kg^{–1}K^{–1}for {Co_{4}Gd_{6}}; and 28.6 J kg^{–1}K^{–1}for {Co_{6}Gd_{8}}, from which we can see these values are proportional to the percentage of the gadolinium in the core.