Issue 6, 2022

Pentacoordinate cobalt(ii) single ion magnets with pendant alkyl chains: shall we go for chloride or bromide?

Abstract

Four pentacoordinate complexes, 1–4, of the type [Co(L1)X2] and [Co(L2)X2] (where L1 = 2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 1 and 2, L2 = 2,6-bis(1-dodecyl-1H-benzimidazol-2-yl)-pyridine for 3 and 4; X = Cl for 1 and 3, X = Br for 2 and 4) have been synthesized, and their structures have been determined by X-ray analysis. The DC magnetic investigation confirmed the high-spin and anisotropic behavior of the metal centers of the reported compounds, and magnetic data were analyzed with respect to the spin Hamiltonian and the Griffith–Figgis Hamiltonian. CASSCF-NEVPT2 analysis enabled us to identify triaxial magnetic anisotropy for 1 and 2 and axial anisotropy for 3 and 4, and we discuss thoroughly the relationship between geometry and orbital ordering. The g-tensor components of the ground Kramers doublet extracted from EPR spectroscopy are compatible with this prediction of magnetic anisotropy. Simulated FIRMS experimental data of 2, 3 and 4 show very good agreement with theoretical calculations and provide precise values of zero-field splitting. The AC susceptibility measurements confirmed that the reported complexes were field-induced single-ion magnets. The slow relaxation of magnetization in 1 and 2 is mediated through two relaxation channels that are unusually close to each other. On the other hand, complexes 3 and 4 show the single-channel relaxation of magnetization, and their isostructural characteristic allowed us to study the relaxation changes caused solely by the replacement of terminal halido ligands. Finally, a wet lithographic technique has been used to evaluate both the processability of the complexes in solution and the preparation of microstructured films.

Graphical abstract: Pentacoordinate cobalt(ii) single ion magnets with pendant alkyl chains: shall we go for chloride or bromide?

Supplementary files

Article information

Article type
Research Article
Submitted
25 Oct 2021
Accepted
13 Jan 2022
First published
14 Jan 2022

Inorg. Chem. Front., 2022,9, 1179-1194

Pentacoordinate cobalt(II) single ion magnets with pendant alkyl chains: shall we go for chloride or bromide?

J. Juráková, J. Dubnická Midlíková, J. Hrubý, A. Kliuikov, V. T. Santana, J. Pavlik, J. Moncoľ, E. Čižmár, M. Orlita, I. Mohelský, P. Neugebauer, D. Gentili, M. Cavallini and I. Šalitroš, Inorg. Chem. Front., 2022, 9, 1179 DOI: 10.1039/D1QI01350E

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