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

Kód výsledku v 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>

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

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

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

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

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10402 - Inorganic and nuclear chemistry

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2024

Kód důvěrnosti údajů

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

Název periodika

Dalton Transactions

ISSN

1477-9226

e-ISSN

1477-9234

Svazek periodika

53

Číslo periodika v rámci svazku

31

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

11

Strana od-do

12962-12972

Kód UT WoS článku

001272690700001

EID výsledku v databázi Scopus

2-s2.0-85199129089