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

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989592%3A15310%2F24%3A73627696" target="_blank" >RIV/61989592:15310/24:73627696 - isvavai.cz</a>

Result on the web

<a href="https://pubs.rsc.org/en/content/articlelanding/2024/dt/d4dt01509f" target="_blank" >https://pubs.rsc.org/en/content/articlelanding/2024/dt/d4dt01509f</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1039/d4dt01509f" target="_blank" >10.1039/d4dt01509f</a>

Result language

angličtina

Original language name

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

Original language description

Four novel Co(ii) coordination compounds 1-4 of the general formula [Co(L-n)(2)][Co(NCY)(4)]&lt;middle dot&gt;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.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10402 - Inorganic and nuclear chemistry

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2024

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Dalton Transactions

ISSN

1477-9226

e-ISSN

1477-9234

Volume of the periodical

53

Issue of the periodical within the volume

31

Country of publishing house

GB - UNITED KINGDOM

Number of pages

11

Pages from-to

12962-12972

UT code for WoS article

001272690700001

EID of the result in the Scopus database

2-s2.0-85199129089