Publication detail

Magnetic anisotropy and slow relaxation of magnetisation in double salts containing four- and six-coordinate cobalt(ii) complex ions

JURÁKOVÁ, J. SANTANA, V. PAVLIK, J. MONCOL, J. NEMEC, I. CLEMENTE-LEON, M. SENTHIL KUMAR, K. RUBEN, M. ČIŽMÁR, E. ŠALITROŠ, I.

Original Title

Magnetic anisotropy and slow relaxation of magnetisation in double salts containing four- and six-coordinate cobalt(ii) complex ions

Type

journal article in Web of Science

Language

English

Original Abstract

Four novel Co(ii) coordination compounds 1-4 of the general formula [Co(L-n)(2)][Co(NCY)(4)]mCH(3)CN (where Ln are tridentate ligands L1 = 2,6-bis(1-hexyl-1H-benzimidazol-2-yl)pyridine for 1 and 2; L2 = 2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 3; L3 = 2,6-bis(1-dodecyl-1H-benzimidazol-2-yl)pyridine for 4, Y = O for 1, 3, and 4 and Y = S for 2; m = 0 for 1 and 3, m = 0.5 for 2 and m = 2 for 4) were prepared and characterised. The molecular structures of all four compounds consist of the hexacoordinate complex cation [Co(L-n)(2)](2+) and tetracoordinate complex anion [Co(NCY)(4)](2-), with distorted octahedral and tetrahedral symmetry of coordination polyhedra, respectively. The electronic structures of all compounds feature an orbitally non-degenerate ground state well-separated from the lowest excited state, which allows the analysis of the magnetic anisotropy by the spin Hamiltonian model. ZFS parameters, derived from both CASSCF-NEVPT2 calculations and magnetic data analysis, indicate that tetrahedral anions [Co(NCY)(4)](2- )exhibit small axial parameters |D| spanning the range of 2.2 to 7.7 cm(-1), while octahedral cations [Co(L-n)(2)](2+) display significantly larger |D| parameters in the range of 37 to 95 cm(-1). For 1-3, the Fourier-transform infrared magnetic spectroscopy (FIRMS) revealed a reasonable transmission with a magnetic absorption around the expected value for the ZFS accompanied by features allowing to identify phonon frequencies and simulate spin-phonon couplings. Dynamic magnetic investigations unveiled the field-induced slow relaxation of magnetisation, with maximal relaxation times (tau) of 92(2) mu s for 2 at 2 K and B-DC = 0.3 T. The temperature evolution of tau was analysed using a combination of Orbach, direct and Raman relaxations (U-eff = 8(1) K (5.6 cm(-1))) or Orbach, direct and spin-phonon induced relaxations (U-eff = 10.3(9) K (7.2 cm(-1))). The rest of the complexes, namely 1, 3, and 4 show field-induced slow relaxation of magnetisation with tau smaller than 16 mu s.

Keywords

SPIN-CROSSOVER; TRANSITIONS

Authors

JURÁKOVÁ, J.; SANTANA, V.; PAVLIK, J.; MONCOL, J.; NEMEC, I.; CLEMENTE-LEON, M.; SENTHIL KUMAR, K.; RUBEN, M.; ČIŽMÁR, E.; ŠALITROŠ, I.

Released

6. 8. 2024

Publisher

ROYAL SOC CHEMISTRY

Location

CAMBRIDGE

ISBN

1477-9234

Periodical

Dalton Transactions

Year of study

53

Number

31

State

United Kingdom of Great Britain and Northern Ireland

Pages from

12962

Pages to

12972

Pages count

11

URL

https://pubs.rsc.org/en/content/articlelanding/2024/dt/d4dt01509fn/

BibTex

@article{BUT189916,
  author="Jana {Juráková} and Vinicius Tadeu {Santana} and Ján {Pavlik} and Ján {Moncol} and Ivan {Nemec} and Miguel {Clemente-Leon} and Kuppusamy Senthil {Kumar} and Mario {Ruben} and Erik {Čižmár} and Ivan {Šalitroš}",
  title="Magnetic anisotropy and slow relaxation of magnetisation in double salts containing four- and six-coordinate cobalt(ii) complex ions",
  journal="Dalton Transactions",
  year="2024",
  volume="53",
  number="31",
  pages="12962--12972",
  doi="10.1039/d4dt01509f",
  issn="1477-9234",
  url="https://pubs.rsc.org/en/content/articlelanding/2024/dt/d4dt01509fn/"
}