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Anions Influence the Relaxation Dynamics of Mono‑μ3‑OH-Capped Triangular Dysprosium Aggregates

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journal contribution
posted on 01.06.2015, 00:00 by Li Zhang, Peng Zhang, Lang Zhao, Jianfeng Wu, Mei Guo, Jinkui Tang
A family of four Dy3 triangular circular helicates, namely, [Dy3(HL)33-OH)­(CH3OH)2(H2O)4]­Cl1.5(OH)0.5·0.5H2O (1), [Dy3(HL)33-OH)­(CH3OH)3(H2O)2Cl]­Cl·CH3OH (2), [Dy3(HL)33-OH)­(CH3OH)3(H2O)2(NO3)]­(NO3) (3), and [Dy3(HL)33-OH)­(CH3OH)4(ClO4)]­(ClO4) (4), were assembled by the reaction of a new acylhydrazone ligand H3L [(3-hydroxy)-N′-((8-hydroxyquinolin-2-yl)­methylene)­picolinohydrazide] with different dysprosium­(III) salts. These compounds represent the first examples of μ-Oacylhydrazone-bridged triangular Dy3 SMMs reported to date. Alternating-current magnetic susceptibility measurements revealed that compounds 1 and 2 show typical SMM behavior with the occurrence of multiple relaxation processes, whereas frequency-dependent relaxation signals without χ″ peaks were observed in 3 and 4 under zero dc field. Such distinct dynamic behaviors are attributed to the different sizes of the terminal coordination solvent/anions (H2O, Cl, NO3, and ClO4 for 14, respectively) at the Dy3 site. Here, similar deviations from the ideal monocapped square-antiprismatic (C4v) geometry defined by SHAPE software were observed around local Dy centers in 1 and 2, whereas the situation was completely different in 3 and 4 as a result of the presence of relatively large anions in the limited space defined by three intercrossing rigid hydrazone ligands.