Synthesis and Magnetism of Neutral, Linear Metallocene Complexes of Terbium(II) and Dysprosium(II)
2019
Gould, Colin A. | McClain, K Randall | Yu, Jason M. | Groshens, Thomas J. | Furche, Filipp | Harvey, Benjamin G. | Long, Jeffrey R.
The divalent metallocene complexes Ln(Cpⁱᴾʳ⁵)₂ (Ln = Tb, Dy) were synthesized through the KC₈ reduction of Ln(Cpⁱᴾʳ⁵)₂I intermediates and represent the first examples of neutral, linear metallocenes for these elements. X-ray diffraction analysis, density functional theory calculations, and magnetic susceptibility measurements indicate a 4fⁿ5d¹ electron configuration with strong s/d mixing that supports the linear coordination geometry. A comparison of the magnetic relaxation behavior of the two divalent metallocenes relative to salts of their trivalent counterparts, [Ln(Cpⁱᴾʳ⁵)₂][B(C₆F₅)₄], reveals that lanthanide reduction has opposing effects for dysprosium and terbium, with magnetic relaxation times increasing from Tbᴵᴵᴵ to Tbᴵᴵ and decreasing from Dyᴵᴵᴵ to Dyᴵᴵ. The impact of this effect is most notably evident for Tb(Cpⁱᴾʳ⁵)₂, which displays an effective thermal barrier to magnetic relaxation of 1205 cm–¹ and a 100-s blocking temperature of 52 K, the highest values yet observed for any nondysprosium single-molecule magnet.
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