Source: School of Chemistry

Written by: School of Chemistry

Edited by: Jin Feng

Single-molecule magnets (SMMs) have attracted enormous and multidisciplinary research studies in the past few decades, since their non-trivial memory effect and quantum phenomena give rise to their potential applications in ultra-high density data storage, quantum computing and spintronics. Unlike conventional bulk magnets, SMMs are quantized systems in which the spin of a molecule can be trapped in either of the bistable states. Consequently, the magnetization is retained below blocking temperature (T_B) unless it is assisted by quantum tunneling of magnetization (QTM) or spin–lattice relaxation, and the key to affect T_B and effective energy barrier is axial/transverse magnetic anisotropy of the molecule. In recent years, lanthanide-based single-molecule magnets (Ln-SMMs) have become the most eye-catching and the most high-performance SMMs.

Prof. Ming-Liang Tong’s group from School of Chemistry at Sun Yat-Sen University proposed that transverse magnetic anisotropy and QTM can be potentially suppressed under the ligand-charge distribution of D_5hsymmetry for Ln-SMMs. and it has been further identified by synthesis a series of high-performance Ln-SMMs with pentagonal-bipyramidal coordination geometry (Chem. Sci. 2013, 4, 3310; Angew. Chem. Int. Ed. 2014, 53, 12966; J. Am. Chem. Soc. 2016, 138, 5441; J. Am. Chem. Soc. 2016, 138, 2829).

To summarize the symmetry strategies for high performance Ln-SMMs in chemical society, Dr. Jun-Liang Liu, Dr. Yan-Cong Chen, and Prof. Dr. Ming-Liang Tong published a review article (Chem. Soc. Rev. 2018, DOI: 10.1039/C7CS00266A). In this review, crystal-field theory is employed to demonstrate the electronic structures according to the semiquantitative electrostatic model. Then, specific symmetry elements are analyzed for the elimination of transverse crystal fields and QTM in theory. In this way, high-performance Ln-SMMs can be designed to enable extremely slow relaxation of magnetization, namely magnetic blocking; however, their practical magnetic characterization becomes increasingly challenging. Therefore, the experimental issues are interpreted and clarified in detail. Finally, representative Ln-SMMs with specific local symmetries are summarized in combination with the discussion on the symmetry strategies, and some open questions await to answer are put forward.

This work was supported by the National Natural Science Foundation of China, the Fundamental Research Funds for the Central Universities and the National Postdoctoral Program for Innovative Talents from China Postdoctoral Science Foundation.

Link to the article: http://pubs.rsc.org/en/Content/ArticleLanding/2018/CS/C7CS00266A