Slow Magnetic Relaxation at Zero Field in the Tetrahedral Complex [Co(SPh)₄]^2–

Abstract

The Ph(4)P(+) salt of the tetrahedral complex [Co(SPh)(4)](2-), possessing an S = (3)/(2) ground state with an axial zero-field splitting of D = -70 cm(-1), displays single-molecule magnet behavior in the absence of an applied magnetic field. At very low temperatures, ac magnetic susceptibility data show the magnetic relaxation time, τ, to be temperature-independent, while above 2.5 K thermally activated Arrhenius behavior is apparent with U(eff) = 21(1) cm(-1) and τ(0) = 1.0(3) × 10(-7) s. Under an applied field of 1 kOe, τ more closely approximates Arrhenius behavior over the entire temperature range. Upon dilution of the complex within a matrix of the isomorphous compound (Ph(4)P)(2)[Zn(SPh)(4)], ac susceptibility data reveal the molecular nature of the slow magnetic relaxation and indicate that the quantum tunneling pathway observed at low temperatures is likely mediated by intermolecular dipolar interactions.

Slow Magnetic Relaxation in Chiral Helicene-Based Coordination Complex of Dysprosium

“…Indeed, the coupling of spin-phonon degrees of freedom in the SMM relaxation is not taken into account in the ab initio model whereas it has been recently evidenced of general importance [49,50]. However, these discrepancies are common in literature [3,51,52] and the magnetic transition moments calculated in this work still leads to a fairly good qualitative picture. Indeed, no direct transition between the two M J states of the ground doublet or Orbach processes from the ground state are expected whereas relaxation mechanisms involving states from the third M J state are highly probable.…”

Evidence of Slow Magnetic Relaxation in Co(AcO)2(py)2(H2O)2

“…The double well model holds up in the case of monometallic cobalt(II) SMMs with negative D values [9,[11][12][13][14][15][16][17][18][19], but the observation of similar behaviour in monometallic cobalt(II) complexes with positive D values [20][21][22] suggests that the picture is more complex. Indeed, slow relaxation in positive-D compounds is a phenomenon that is not yet fully understood-although attempts have been made to explain it [23,24].…”

Diamagnetic cobalt(III)tris(o-ethylxanthate) and nickel(II)bis(o-ethylxanthate)

“…In course of time a plethora 3d-metal complexes were identified as SMMs, including simple mononuclear systems containing Mn(III) (Grigoropoulos et al 2013), Fe(III) (Mossin et al 2012), Fe(II) , Fe(I) (Samuel et al 2014), Co(II) , Ni(II) (Lomjansky et al 2017), Ni(I) (Lin et al 2016) and Cu(II) central atoms (Frost et al 2016). Among these systems, the S-donor ligands combined with the cobalt(II) centres attract a considerable attention because of the pronounced magnetic anisotropy that supports the SMM behaviour (Zadrozny and Long 2011). However, Co(II) can be readily oxidized to Co(III) in course of the complexation reaction on air giving rise the diamagnetic complex.…”