Slow magnetic relaxation in a Dy3 triangle and a bistriangular Dy6 cluster

Abstract

Two lanthanide single-molecule magnets (SMMs) [Dy₃(μ₃-OH)(HL-1)₃(H₂O)₃](NO₃)₂·3H₃O (1, H₃L-1 = (E)-3-(((8-hydroxyquinolin-2-yl)methylene)amino)propane-1,2-diol) and [Dy₆(μ₃-OH)₄(H₂L-2)₄(HL-2)₂(L-2)₂] (2, H₃L-2 = (E)-2-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide) were synthesized and characterized structurally and magnetically. Complex 1 contains a triangular Dy₃ core in which the three Dy³⁺ ions share a μ₃-OH⁻ anion and the deprotonated ligands of (HL-1)²⁻ serve both capping and bridging functions, while 2 displays a centrosymmetric hexanuclear Dy^III structure with two similar Dy₃ triangular cores ligated by two fully deprotonated (L-2)³⁻ ligands, each of which shares two μ₃-OH⁻ anions. All the Dy^III ions are eight-coordinated with quasi D_2d or C_2v symmetry. Magnetic studies reveal that 1 exhibited two-step magnetic relaxation under an applied dc field of 800 Oe, with effective energy barriers of 40.1 and 31.0 K for the slow relaxation (SR) and fast relaxation regimes (FR), respectively. Meanwhile, 2 only showed a tail of slow magnetic relaxation at above 2 K. Ab initio calculations have been carried out to show the nature of their different magnetic properties.