An Effectively Uncoupled Gd 8 Cluster Formed through Fixation of Atmospheric CO 2 Showing Excellent Magnetocaloric Properties.

The [Gd 8 (opch) 8 (CO 3 ) 4 (H 2 O) 8 ]·4H 2 O·10MeCN coordination cluster ( 1 ) crystallises in P1¯. The Gd 8 core is held together by four bridging carbonates derived from atmospheric CO 2 as well as the carboxyhydrazonyl oxygens of the 2-hydroxy-3-methoxybenzylidenepyrazine-2-carbohydrazide (H 2 opch) Schiff base ligands. The magnetic measurements show that the Gd III ions are effectively uncoupled as seen from the low Weiss constant of 0.05 K needed to fit the inverse susceptibility to the Curie-Weiss law. Furthermore, the magnetisation data are consistent with the Brillouin function for eight independent Gd III ions. These features lead to a magnetocaloric effect with a high efficiency which is 89% of the theoretical maximum value.