Magnetochemistry (Nov 2022)

Mononuclear Heptacoordinated 3d-Metal Helicates as a New Family of Single Ion Magnets

  • Yulia P. Tupolova,
  • Denis V. Korchagin,
  • Anastasya S. Andreeva,
  • Valery V. Tkachev,
  • Gennadii V. Shilov,
  • Vladimir A. Lazarenko,
  • Leonid D. Popov,
  • Konstantin A. Babeshkin,
  • Nikolay N. Efimov,
  • Roman B. Morgunov,
  • Andrei V. Palii,
  • Stanislav P. Kubrin,
  • Igor N. Shcherbakov,
  • Sergey M. Aldoshin

DOI
https://doi.org/10.3390/magnetochemistry8110153
Journal volume & issue
Vol. 8, no. 11
p. 153

Abstract

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The series of Co(II), Fe(II), and Ni(II) mononuclear coordination compounds of [CoL(NCS)2]·3DMSO (1), [CoL(H2O)2](ClO4)2·DMSO (2), [CoL(H2O)(EtOH)][CoCl4]·2H2O (2a), [FeL(NCS)2]·DMSO (3), and [NiL(NCS)2]·CH3CN (4) composition (where L is 2,6-bis(1-(2-(4,6-dimethylpyrimidin-2-yl)hydrazineylidene)ethyl)pyridine), with an [MLA2] coordination unit (where A is a pair of apical monodentate ligands), was synthesized. In compounds 1, 2, 2a, and 3, the ligand L is pentadentate, and cobalt and iron ions are placed in a heavily distorted pentagonal pyramidal coordination environment, while in 4 the Ni(II) ion is hexacoordinated. Easy plane-type magnetic anisotropy (D = 13.69, 11.46, 19.5, and 6.2 cm−1 for 1, 2, 2a, and 4, respectively) was established for cobalt and nickel compounds, while easy axis-type magnetic anisotropy (D = −14.5 cm−1) was established for iron compound 3. The cobalt coordination compounds 1 and 2 show SIM behavior under a 1500 Oe external magnetic field, with effective magnetization reversal barriers of 65(1) and 60(1) K for 1 and 2, respectively. The combination of Orbach and Raman relaxation mechanisms was shown to adequately describe the temperature dependence of relaxation times for 1 and 2. CASSCF/NEVPT2 calculations were performed to model the parameters of the effective spin Hamiltonian for the compounds under study.

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