Structure and Magnetic Properties of a Series of Heptanuclear Ln₃Mn₄ Molecular Clusters Constructed with Phenyl-salicylaldoxime: Observation of a Significant Magnetocaloric Effect in Gd₃Mn₄

Magnetic polymetallic cluster compounds, with their variable structures and intricate magnetic properties, have garnered sustained interest in molecular magnetism. In this study, we constructed a series of isostructural heptanuclear 3d–4f clusters using phenyl-salicylaldoxime as a multidentate ligand, represented by the general formula [Ln3Mn4] (Ln = Gd, Dy, Tb, Er, and Y for 1Gd, 2Dy, 3Tb, 4Er, and 5Y, respectively). Comprehensive crystallographic analyses and static magnetism studies were performed on these compounds. The magnetic investigations indicate that at low temperatures and high fields, the metal ions exhibit parallel alignment of magnetic moments, resulting in a large spin value. Notably, 1Gd displayed a significant magnetocaloric effect (MCE) owing to its high ground-state spin and robust temperature and field responsiveness, with a magnetic entropy change (−ΔSm) of 20.99 J kg–1 K–1 at 50 kOe and 6.0 K in the range of measurements, highlighting its potential as a promising candidate for magnetic refrigeration applications.