A Family of 3d-4f Octa-Nuclear [MnIII 4LnIII 4] Wheels (Ln = Sm, Gd, Tb, Dy, Ho, Er, and Y): Synthesis, Structure, and Magnetism

• Published in: Inorganic chemistry 2010-12, Vol.49 (24), p.11587-11594
• Main Authors: Li, Mengyuan, Lan, Yanhua, Ako, Ayuk M, Wernsdorfer, Wolfgang, Anson, Christopher E, Buth, Gernot, Powell, Annie K, Wang, Zheming, Gao, Song
• Format: Article
• Language: English
• Subjects: Physics
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic101754g

We present the syntheses, crystal structures, and magnetochemical characterizations for a family of isostructural [Mn4Ln4] compounds (Ln = Sm, Gd, Tb, Dy, Ho, Er, and Y). They were prepared from the reactions of formic acid, propionic acid, N-n-butyl-diethanolamine, manganese perchlorate, and lanthanide nitrates under the addition of triethylamine in MeOH. The compounds possess an intriguing hetero-octanuclear wheel structure with four MnIII and four LnIII ions alternatively arranged in a saddle-like ring, where formate ions act as key carboxylate bridges. In the lattice, the molecules stack into columns in a quasi-hexagonal arrangement. Direct current (dc) magnetic susceptibility measurements indicated the depopulation of the Stark components at low temperature and/or very weak antiferromagnetic interactions between magnetic centers. The zero-field alternating current (ac) susceptibility studies revealed that the compounds containing Sm, Tb, and Dy showed frequency-dependent out-of-phase signals, indicating they are single-molecule magnets (SMMs). Magnetization versus applied dc field sweeps on a single crystal of the Dy compound down to 40 mK exhibited hysteresis depending on temperatures and field sweeping rates, further confirming that the Dy compound is a SMM. The magnetization dynamics of the Sm and Y compounds investigated under dc fields revealed that the relaxation of the Sm compound is considered to be dominated by the two-phonon (Orbach) process while the Y compound displays a multiple relaxation process.