Slow Magnetic Relaxation in a High-spin Iron(II) Complex
(Graph Presented) Slow magnetic relaxation is observed for [(tpa Mes)Fe] -, a trigonal pyramidal complex of high-spin iron(II), providing the first example of a mononuclear transition metal complex that behaves as a single-molecule magnet. Dc magnetic susceptibility and magnetization measurements reveal a strong uniaxial magnetic anisotropy (D = -39.6 cm -1) acting on the S = 2 ground state of the molecule. Ac magnetic susceptibility measurements indicate the absence of slow relaxation under zero applied dc field as a result of quantum tunneling of the magnetization. Application of a 1500 Oe dc field initiates slow magnetic relaxation, which follows a thermally activated tunneling mechanism at high temperature to give an effective spin-reversal barrier of U eff = 42 cm -1 and follows a temperature-independent tunneling mechanism at low temperature. In addition, the magnetic relaxation time shows a pronounced dc-field dependence, with a maximum occurring at ∼1500 Oe. Copyright © 2010 American Chemical Society.
D. E. Freedman et al., "Slow Magnetic Relaxation in a High-spin Iron(II) Complex," Journal of the American Chemical Society, American Chemical Society (ACS), Jan 2010.
The definitive version is available at http://dx.doi.org/10.1021/ja909560d
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