CuII-GdIII Cryogenic Magnetic Refrigerants and Cu8Dy9 Single-Molecule Magnet Generated by In Situ Reactions of Picolinaldehyde and Acetylpyridine: Experimental and Theoretical Study

A series of heterometallic [Ln(x)(III)Cu(y)(II)] complexes, [Gd2Cu2](n) (1), [Gd4Cu8] (2), [Ln(9)Cu(8)] (Ln=Gd, 3Gd; Ln=Dy, 3Dy), 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 [GdxCuy] 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 [Dy9Cu8] complexes, local magnetic properties of the Dy-III centers have been determined by using the CASSCF+RASSI method.