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.