[Show abstract][Hide abstract] ABSTRACT: In the area of molecular magnetism, single molecule magnets (SMMs) containing lanthanide elements are of immense scientific and technological interest because of their large energy barriers and high measured hysteresis temperature. Although there has been significant progress in the synthesis and characterization of lanthanide-based SMMs, there are still challenges, for instance, how single-ion anisotropy of lanthanide elements can be exploited, and how zero-field tunneling of magnetization can be suppressed. This article is devoted to the progress in various methodologies for modulating magnetic relaxation, especially in terms of crystal field and magnetic interactions. The crystal field plays a dominant role in creating single-molecule magnets with largely anisotropic f-elements, while the strong coupling between magnetic centers is able to suppress quantum tunneling of magnetization efficiently.
Chinese Science Bulletin 01/2014; 57(20). · 1.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Schiff base ligand N1,N3-bis(3-methoxysalicylidene)diethylenetriamine (H2 valdien) and the co-ligand 6-chloro-2-hydroxypyridine (Hchp) were used to construct two 3d-4f heterometallic single-ion magnets [Co2 Dy(valdien)2 (OCH3 )2 (chp)2 ]⋅ClO4 ⋅5 H2 O (1) and [Co2 Tb(valdien)2 (OCH3 )2 (chp)2 ]⋅ClO4 ⋅2 H2 O⋅CH3 OH (2). The two trinuclear [Co(III) 2 Ln(III) ] complexes behave as a mononuclear Ln(III) magnetic system because of the presence of two diamagnetic cobalt(III) ions. Complex 1 has a molecular symmetry center, and it crystallizes in the C2/c space group, whereas complex 2 shows a lower molecular symmetry and crystallizes in the P21 /c space group. Magnetic investigations indicated that both complexes are field-induced single-ion magnets, and the Co(III) 2 -Dy(III) complex possesses a larger energy barrier [74.1(4.2) K] than the Co(III) 2 -Tb(III) complex [32.3(2.6) K].
Chemistry - An Asian Journal 05/2014; · 4.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Single-molecule magnets are compounds that exhibit magnetic bistability purely of molecular origin. The control of anisotropy and suppression of quantum tunneling to obtain a comprehensive picture of the relaxation pathway manifold, is of utmost importance with the ultimate goal of slowing the relaxation dynamics within single-molecule magnets to facilitate their potential applications. Combined ab initio calculations and detailed magnetization dynamics studies reveal the unprecedented relaxation mediated via the second excited state within a new DyNCN system comprising a valence-localized carbon coordinated to a single dysprosium(III) ion. The essentially C2v symmetry of the Dy(III) ion results in a new relaxation mechanism, hitherto unknown for mononuclear Dy(III) complexes, opening new perspectives for means of enhancing the anisotropy contribution to the spin-relaxation barrier.
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