Three Phenoxo‐Bridged Dinuclear Lanthanide Complexes: Syntheses, Crystal Structures, and Magnetic Properties

Three dinuclear lanthanide complexes [ Ln 2 (H 2 L) 2 (NO 3 ) 4 ] [ Ln = Dy ( 1 ), Tb ( 2 ), and Gd ( 3 )] [H 3 L = 2‐hydroxyimino‐ N ′‐[(2‐hydroxy‐3‐methoxyphenyl)methylidene]‐propanohydrazone] were solvothermally synthesized by varying differently anisotropic rare earth ions. Single‐crystal structural analyses demonstrate that all the three complexes are crystallographically isostructural with two centrosymmetric Ln III ions aggregated by a pair of monodeprotonated H 2 L – anions. Weak intramolecular antiferromagnetic interactions with different strength were mediated by a pair of phenoxo bridges due to superexchange and/or single‐ion anisotropy. Additionally, the Dy III ‐based entity shows the strongest anisotropy exhibits field‐induced single‐molecule magnetic behavior with two thermally activated relaxation processes. In contrast, 3 with isotropic Gd III ion has a significant cryogenic magnetocaloric effect with the maximum entropy change of 25.7 J · kg –1 · K –1 at 2.0 K and 70.0 kOe.