The Interactions Between the Well-Isolated Dy3+ Ions Considerably Contribute to the Demagnetization of Mononuclear Acetylacetonate-Pyrazinate Complex

Abstract

A series of new mononuclear square antiprismatic complexes comprising acetylacetonate (acac-), pyrazine-2-carboxylate (PyrCOO-) and 1,10-phenanthroline (phen) ligands namely [Ln(acac)2(PyrCOO)(phen)] (Ln is Dy-Yb, Y; 1-5, 6) were prepared and studied. These complexes are new examples of extremely scarcely studied eight-coordinated tetra-chelate complexes comprising β-diketonate and carboxylate ligands. Complexes 1, 3 and 5 exhibit pronounced slowdown of the demagnetization with corresponding pathways additionally validated by the ab initio calculations. In particular, complex 1 exhibits zero-field relaxation with Δeff/kB of 149 K, while the application of the optimal DC field (1500 Oe) enhances Δeff/kB value to 265 K. Thus, although the quantum tunneling of magnetization (QTM) contributes to zero-field relaxation of complex 1, it is among the most efficient zero-field Dy-based SMMs formed by β-diketonate and/or carboxylate ligands. Moreover, Δeff/kB value under the optimal field is the highest one among the related complexes. Interestingly, the Dy-Dy magnetic interactions have considerable effect on the SMM performance of 1 even given the spatial (>8 Å) separation of Dy3+ ions isolated by coats of bulky diamagnetic ligands.