Cu II Gd III Cryogenic Magnetic Refrigerants and Cu 8 Dy 9 Single‐Molecule Magnet Generated by In Situ Reactions of Picolinaldehyde and Acetylpyridine: Experimental and Theoretical Study

A series of heterometallic [Ln III x Cu II y ] complexes, [Gd 2 Cu 2 ] n ( 1 ), [Gd 4 Cu 8 ] ( 2 ), [Ln 9 Cu 8 ] (Ln=Gd, 3⋅Gd ; Ln=Dy, 3⋅Dy ), were successfully synthesized by a one‐pot route at room temperature with three kinds of in situ carbonyl‐related reactions: Cannizzaro reaction, aldol reaction, and oxidation. This strategy led to dysprosium analogues that behaved as single‐molecule magnets (SMMs) and gadolinium analogues that showed significant magnetocaloric effect (MCE). In this study a numerical DFT approach is proposed by using pseudopotentials to calculate the exchange coupling constants in three polynuclear [Gd x Cu y ] complexes; with these values exact diagonalization or quantum Monte Carlo simulations have been performed to calculate the variation of the magnetic entropy involved in the MCE. For the [Dy 9 Cu 8 ] complexes, local magnetic properties of the Dy III centers have been determined by using the CASSCF+RASSI method.