Playing with Magnetic Anisotropy in Hexacoordinated Mononuclear Ni(II) Complexes, An Interplay Between Symmetry and Geometry

Abstract

The magnetic anisotropy parameters of a hexacoordinate trigonally elongated Ni(II) complex with symmetry close to D3d are measured using field-dependent magnetization and High-Field and High-Frequency EPR spectroscopy (D = +2.95 cm -1 , |E/D| = 0.08 from EPR). Wavefunction based theoretical calculations reproduce fairly well the EPR experimental data and allows analysing the origin of the magnetic anisotropy of the complex. Calculations on model complexes allows getting insight into the origin of the large increase in the axial magnetic anisotropy (D) when the complex is brought to a prismatic geometry with a symmetry close to D3h .

Ligand design of zero-field splitting in trigonal prismatic Ni(ii) cage complexes

“…Separate analyses suggest that α is the central parameter for affecting ZFS and electronic structure in similar complexes. 50,64 Yet there does not appear to be a correlation between α and D in our data. Owing to the foregoing points, it is thus challenging to attribute one sole feature to the modification of D, necessitating future studies to fully understand the variation.…”

“…49 Furthermore, as noted above, the susceptibility fits seemed insensitive to sign and magnitude of E. It is for these reasons that we report |E| in Table 1 rather than the sign. Previous computational analyses of trigonal prismatic Ni(II) complexes, 50 as well as first-principle predictions based on the possible 3d-orbital excitations for a D 3h d 8 ion, indicate that the sign of D should be positive. 51,52 This conclusion is also supported by χ M T trending towards zero as the systems reach an M s = 0 ground state.…”

“…A complicating feature in the analysis of the D trend is that the changes to the coordination geometries with functional groups are minor, 63 but may be significant for the zero-field splitting. 50 From 1 to 5, an increase in D is observed with an increase in the average Ni-N distance across the series with 1 showing the shortest Ni-N distances (ca. 1.996 Å) and lowest D value, and 5 showing the highest Ni-N distances (ca.…”

Chemical tuning of spin clock transitions in molecular monomers based on nuclear spin-free Ni(ii)

“…Getting insight of the contribution of each state by analysing the composition of their wave function is possible, as it has recently been done on a Ni( ii ) complex with an octahedral geometry, 44 but is out of the scope of this paper. These results confirm our reasoning that a Ni( ii ) hexacoordinate complex with octahedral geometry that slightly deviates from O h symmetry leads to small D value and consequently small E (as | E | < | D |/3).…”

Magnetic Hysteresis in a Monolayer of Oriented 6 nm CsNiCr Prussian Blue Analogue Nanocrystals

“…The magnetic anisotropy of the nanocrystals and its nature (easy axis/easy plane) are directly related to the anisotropy of the single nanocrystals that have its origin in the single-ion anisotropy of the metal ions. The single-ion anisotropy (magnetocrystalline anisotropy) is due to the conjugated effects of spin–orbit coupling (SOC) and an anisotropy of the ion electronic cloud, − the latter can be assessed for an oriented single layer by XNLD …”