Dysprosium Clusters from 3-Ethoxysalicylidene Terminal-Decorated Acylhydrazone Ligands: In Situ Ligand Transformation-Assisted Assembly and Zero-Field Single-Molecule Magnet Behaviors

Abstract

High-performance polynuclear lanthanide single-molecule magnets (Ln-SMMs) are still scarce now. Herein, we report the assembly of three novel Dy III clusters, where in situ ligand transformation-assisted assembly offered a system with high SMM performance successfully. These clusters, [Dy 6 (bepho) 3 (NO 3 ) 6 (CH 3 OH) 3 (H 2 O) 3 ]•5CH 3 OH•CH 3 CN•2H 2 O (1), [Dy 4 (bepho) 2 (H 3 epho) 2 (CH 3 OH) 2 ]•2CH 3 OH (2), and [Dy 5 (eehz) 3 (eqzl)(μ-CH 3 O)(μ 3 -CH 3 O) 2 (μ 4 -O)(CH 3 OH)]•2CH 3 OH (3), were all assembled from 3-ethoxysalicylidene terminal-decorated acylhydrazones. H 4 bepho, H 5 epho, H 3 eehz, and Heqzl represent N,N′-bis(3-ethoxysalicylicdene)pyridine-2,6-dicarbohydrazide N-oxide, N-(3-ethoxysalicylidene)pyridine-2,6-dicarbohydrazide N-oxide, N-(3-ethoxysalicylicdene)-2-(3-ethoxysalicylideneamino)benzohydrazide, and 3-(3-ethoxysalicylicdeneamino)quinazolinone, respectively. Cluster 1 is built by H 4 bepho directly, showing a hexanuclear zig-zag chain structure, while for 2 and 3, their original ligands all undergo unprecedented in situ transformations during the assembly. H 5 epho featuring asymmetric chelating arms and Heqzl bearing the quinazolinone parent are formed in 2 and 3, respectively, and participate in the assembly of clusters along with original ligands. In 2, H 4 bepho and H 5 epho construct a quasi-linear {Dy 4 } topology. A unique pentanuclear core of 3 is assembled by H 3 eehz and Heqzl. It consists of a [Dy 4 ] tetrahedron and a [Dy 3 ] triangle unit sharing an edge. Clusters 1−3 all show zero-field SMM behaviors, and 2 displays two distinct relaxation processes. Strikingly, the quantum tunneling of magnetization (QTM) effect in 3 might be suppressed by intramolecular magnetic interactions associated with its unique cluster topology. The zero-field energy barrier (U eff ) of 3 reaches up to 211.3 K, which is among the high values for all polynuclear Ln-SMM species and also the second largest one in the {Ln 5 }-SMM family.

Structures and Single-Molecule Magnet Behavior of Dy3 and Dy4 Clusters Constructed by Different Dysprosium(III) Salts

“…To explore the magneto-structural correlations of tetranuclear Dy III -based SMMs, this class of complexes were summarized (Table S13). − The nuclear centers of tetranuclear Dy III complexes have various shapes such as linear, cymbiform, and parallelogram. (Figure ).…”