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There is still great potential to be tapped for polynuclear lanthanide single molecule magnets (Ln-SMMs) in performance. Towards this goal, the exploration of polynuclear lanthanide clusters (PLnCs) with novel special...

Endowing lanthanide single-ion magnets (Ln-SIMs) with high stability and stimulus responsiveness is of significance for the practical applications of these novel magnetic materials, but still of challenge at present. Herein, we report on a highly stable and photoresponsive Ln-SIM system achieved by designing and synthesizing a π•••π interaction-stacked framework based on Dy III -SIM (πOF-1). Its molecular formula is [Dy(thqa)] (H 3 thqa = tris[(8-hydroxyquinoline-2-yl)methylene]amino). Each of its C 3 -symmetric molecules consists of a thqa 3− ligand and a Dy III ion, and it is linked to three neighbors by intermolecular π•••π interactions, forming a supermolecular two-dimensional (2D) honeycombed topology. Such unique structure endows πOF-1 with not only air and thermal stability but also excellent chemical stability in different solvents, even in alkali solutions, including a 20 M NaOH aqueous solution. Dual magnetic relaxation behavior was observed in πOF-1. Magnetic dilution revealed that it is related to π•••π-mediated intermolecular magnetic interactions. More significantly, both the static magnetic susceptibility and the dual-relaxation behavior of πOF-1 show response to photoirradiation, which could be ascribed to the photo-triggered intermolecular π → π* charge transfer (CT). So far as we know, πOF-1 could be the first Ln-SIM system possessing both a high stability and photoresponsiveness, and also the first photoresponsive Ln-SIM supermolecular system that does not rely on the single-crystal to single-crystal (SCSC) structural transformation. Its successful design and synthesis suggests that the introduction of π•••π interactions can be a new strategy to fabricate stable and/or photoresponsive Ln-SIMs.

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.