Field-Induced Slow Magnetic Relaxation in an Octacoordinated Fe(II) Complex with Pseudo-D2d Symmetry: Magnetic, HF-EPR, and Theoretical Investigations

Guo-Ling Li; Shu-Qi Wu; Li-Fang Zhang; Zhenxing Wang; Zhong-Wen Ouyang; Zhong-Hai Ni; Sheng-Qun Su; Zi-Shuo Yao; Jun-Qiu Li; Osamu Sato

doi:10.1021/acs.inorgchem.7b00765

Field-Induced Slow Magnetic Relaxation in an Octacoordinated Fe(II) Complex with Pseudo-D_2d Symmetry: Magnetic, HF-EPR, and Theoretical Investigations

Inorg Chem. 2017 Jul 17;56(14):8018-8025. doi: 10.1021/acs.inorgchem.7b00765. Epub 2017 Jul 3.

Authors

Guo-Ling Li^{1

2}, Shu-Qi Wu¹, Li-Fang Zhang², Zhenxing Wang³, Zhong-Wen Ouyang³, Zhong-Hai Ni², Sheng-Qun Su¹, Zi-Shuo Yao¹, Jun-Qiu Li¹, Osamu Sato¹

Affiliations

¹ Institute for Materials Chemistry and Engineering & IRCCS, Kyushu University , 744 Motooka Nishi-ku, 819-0395 Fukuoka, Japan.
² School of Chemical Engineering and Technology, China University of Mining and Technology , Xuzhou 221116, People's Republic of China.
³ Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology , Wuhan 430074, People's Republic of China.

PMID: 28671823
DOI: 10.1021/acs.inorgchem.7b00765

Abstract

An octacoordinated Fe(II) complex, [Fe^II(dpphen)₂](BF₄)₂·1.3H₂O (1; dpphen = 2,9-bis(pyrazol-1-yl)-1,10-phenanthroline), with a pseudo-D_2d-symmetric metal center has been synthesized. Magnetic, high-frequency/-field electron paramagnetic resonance (HF-EPR), and theoretical investigations reveal that 1 is characterized by uniaxial magnetic anisotropy with a negative axial zero-field splitting (ZFS) (D ≈ -6.0 cm^-1) and a very small rhombic ZFS (E ≈ 0.04 cm^-1). Under applied dc magnetic fields, complex 1 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 1 has been clearly understood from theoretical calculations. Our study suggests that high-coordinated compounds featuring a D_2d-symmetric metal center are promising candidates for mononuclear single-molecule magnets.