Butterfly-shaped pentanuclear dysprosium single-molecule magnets.
Two new "butterfly-shaped" pentanuclear dysprosium(III) clusters, [Dy5(μ3-OH)3(opch)6(H2O)3]⋅3 MeOH⋅9 H2O (1) and [Dy5(μ3-OH)3(Hopch)2(opch)4(MeOH)(H2O)2]⋅(ClO4)2⋅6 MeOH⋅4 H2O (2), which were based on the heterodonor-chelating ligand o-vanillin pyrazine acylhydrazone (H2opch), have been successfully synthesized by applying different reaction conditions. Single-crystal X-ray diffraction analysis revealed that the butterfly-shaped cores in both compounds were comparable. However, their magnetic properties were drastically different. Indeed, compound 1 showed dual slow-relaxation processes with a transition between them that corresponded to energy gaps (Δ) of 8.1 and 37.9 K and pre-exponential factors (τ0) of 1.7×10(-5) and 9.7×10(-8)  s for the low- and high-temperature domains, respectively, whilst only a single relaxation process was noted for compound 2 (Δ = 197 K, τ0 = 3.2×10(-9)  s). These significant disparities are most likely due to the versatile coordination of the H2opch ligands with particular keto-enol tautomerism, which alters the strength of the local crystal field and, hence, the nature or direction of the easy axes of anisotropic dysprosium ions.
State Key Laboratory of Rare Earth, Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, Changchun 130022 (P.R. China), Fax: (+86) 431 85262878; State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (P.R. China).
Haiquan
H
Tian
Lang
L
Zhao
Haifeng
H
Lin
Jinkui
J
Tang
Guangshe
G
Li
cluster compounds; dysprosium; magnetic properties; single-molecule magnets; tautomerism