Trinuclear Dy(III) Single‐Molecule Magnets with Two‐Step Relaxation

Comprehensive Summary The reaction of DyCl 3 ⋅6H 2 O with a rigid diacylhydrazone ligand (H 2 L) afforded a trinuclear precursor [Dy 3 L 2 Cl 3 (H 2 O) 2 (CH 3 OH)]Cl 2 ⋅3CH 3 OH ( 1 ). The replacement of the Cl – ions and the coordinating solvents by the aryloxides ligands (L x ) – yields three trinuclear complexes [Dy 3 L 2 (L x ) 5 ]⋅n sol ( x = 1,2‐naphthol ( 2 ); x = 2,7‐hydroxycoumarin ( 3 ); and x = 3, phenol ( 4 )). In complexes 2 — 4 , two end Dy 3+ centers adopt almost identical N 4 O 4 coordination sphere of D 6h geometry while the central one adopts N 4 O 5 coordination sphere in C s geometry. Magnetic measurements reveal weak antiferromagnetic interactions in the hydrated samples 2e — 4e and two‐step slow relaxation process under zero dc field with effective energy barriers U eff of 439 and 91 K, 353 and 40 K, 466 and 89 K for SR and FR in 2e — 4e , respectively. Such dynamic magnetic behaviour for 4 persists in the magnetically diluted sample of 4 @Y. Complex 4 possesses the short Dy‐O aryloxide bond distance of 2.055(18) Å, and the largest U eff among the reported linear trinuclear dysprosium complexes. Moreover, the functionalized aryloxides ligands (L x ) – show photoluminescence via intramolecular energy transfer, making 2e — 4e luminescent Dy 3+ SMMs with high energy barriers.