Magnetic Properties of a Dinuclear Nickel(II) Complex with 2,6-Bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate

Hiroshi Sakiyama; Yukako Chiba; Katsuya Tone; Mikio Yamasaki; Masahiro Mikuriya; J Krzystek; Andrew Ozarowski

doi:10.1021/acs.inorgchem.6b01671

Magnetic Properties of a Dinuclear Nickel(II) Complex with 2,6-Bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate

Inorg Chem. 2017 Jan 3;56(1):138-146. doi: 10.1021/acs.inorgchem.6b01671. Epub 2016 Dec 15.

Authors

Hiroshi Sakiyama¹, Yukako Chiba¹, Katsuya Tone¹, Mikio Yamasaki², Masahiro Mikuriya³, J Krzystek⁴, Andrew Ozarowski⁴

Affiliations

¹ Department of Material and Biological Chemistry, Faculty of Science, Yamagata University , 1-4-12 Kojirakawa, Yamagata 990-8560, Japan.
² X-ray Research Laboratory, Rigaku Corporation , Matsubara 3-9-12, Akishima, Tokyo 196-8666, Japan.
³ Department of Applied Chemistry for Environment and Research Center for Coordination Molecule-based Devices, School of Science and Technology, Kwansei Gakuin University , Gakuen 2-1, Sanda 669-1337, Japan.
⁴ National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States.

PMID: 27976888
DOI: 10.1021/acs.inorgchem.6b01671

Abstract

Magnetic properties of dinuclear nickel(II) complex [Ni₂(sym-hmp)₂](BPh₄)₂·3.5DMF·0.5(2-PrOH) (1), where (sym-hmp)^- is 2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate anion and DMF indicates dimethylformamide, were investigated using high-frequency and -field electron paramagnetic resonance (HFEPR). To magnetically characterize the mononuclear nickel(II) species forming the dimer, its two dinuclear zinc(II) analogues, [Zn₂(sym-hmp)₂](BPh₄)₂·3.5DMF·0.5(2-PrOH) (2) and [Zn₂(sym-hmp)₂](BPh₄)₂·2acetone·2H₂O (2'), were prepared. One of them (2') was structurally characterized by X-ray diffractometry and doped with 5% mol nickel(II) ions to prepare a mixed crystal 3. From the HFEPR results on complex 1 obtained at 40 K, the spin Hamiltonian parameters of the first excited spin state (S = 1) of the dimer were accurately determined as |D₁| = 9.99(2) cm^-1, |E₁| = 1.62(1) cm^-1, and g₁ = [2.25(1), 2.19(2), 2.27(2)], and for the second excited spin state (S = 2) at 150 K estimated as |D₂| ≈ 3.5 cm^-1. From these numbers, the single-ion zero-field splitting (ZFS) parameter of the Ni(II) ions forming the dimer was estimated as |D_Ni| ≈ 10-10.5 cm^-1. The HFEPR spectra of 3 yielded directly the single-ion parameters for D_Ni = +10.1 cm^-1, |E_Ni| = 3.1 cm^-1, and g_iso = 2.2. On the basis of the HFEPR results, the previously obtained magnetic data (Sakiyama, H.; Tone, K.; Yamasaki, M.; Mikuriya, M. Inorg. Chim. Acta 2011, 365, 183) were reanalyzed, and the isotropic interaction parameter between the Ni(II) ions was determined as J = -70 cm^-1 (H_ex = -J S_A·S_B). Finally, density functional theory calculations yielded the J value of -90 cm^-1 in a qualitative agreement with the experiment.