Field-Induced Slow Magnetic Relaxation in an Octacoordinated Fe(II) Complex with Pseudo‑<i>D</i>_2<i>d</i> Symmetry: Magnetic, HF-EPR, and Theoretical Investigations

An octacoordinated Fe­(II) complex, [Fe^II(dpphen)₂]­(BF₄)₂·1.3H₂O (<b>1</b>; dpphen = 2,9-bis­(pyrazol-1-yl)-1,10-phenanthroline), with a pseudo-<i>D</i>_2<i>d</i>-symmetric metal center has been synthesized. Magnetic, high-frequency/-field electron paramagnetic resonance (HF-EPR), and theoretical investigations reveal that <b>1</b> is characterized by uniaxial magnetic anisotropy with a negative axial zero-field splitting (ZFS) (<i>D</i> ≈ −6.0 cm^–1) and a very small rhombic ZFS (<i>E</i> ≈ 0.04 cm^–1). Under applied dc magnetic fields, complex <b>1</b> exhibits slow magnetic relaxation at low temperature. Fitting the relaxation time with the Arrhenius mode combining Orbach and tunneling terms affords a good fit to all the data and yields an effective energy barrier (17.0 cm^–1) close to the energy gap between the ground state and the first excited state. The origin of the strong uniaxial magnetic anisotropy for <b>1</b> has been clearly understood from theoretical calculations. Our study suggests that high-coordinated compounds featuring a <i>D</i>_2<i>d</i>-symmetric metal center are promising candidates for mononuclear single-molecule magnets

Sequential Thermal Dissolution of Huolinguole Lignite in Methanol and Ethanol

Sequential Thermal Dissolution of Huolinguole Lignite in Methanol and Ethano