Extreme g‑Tensor Anisotropy and
Its Insensitivity to Structural Distortions in a Family of Linear
Two-Coordinate Ni(I) Bis-N-heterocyclic Carbene Complexes
posted on 2022-01-10, 17:03authored byWilliam
J. M. Blackaby, Katie L. M. Harriman, Samuel M. Greer, Andrea Folli, Stephen Hill, Vera Krewald, Mary F. Mahon, Damien M. Murphy, Muralee Murugesu, Emma Richards, Elizaveta Suturina, Michael K. Whittlesey
We
report a new series of homoleptic Ni(I) bis-N-heterocyclic carbene
complexes with a range of torsion angles between the two ligands from
68° to 90°. Electron paramagnetic resonance measurements
revealed a strongly anisotropic g-tensor in all complexes
with a small variation in g∥ ∼
5.7–5.9 and g⊥ ∼
0.6. The energy of the first excited state identified by variable-field
far-infrared magnetic spectroscopy and SOC-CASSCF/NEVPT2 calculations
is in the range 270–650 cm–1. Magnetic relaxation
measured by alternating current susceptibility up to 10 K is dominated
by Raman and direct processes. Ab initio ligand-field
analysis reveals that a torsion angle of <90° causes the splitting
between doubly occupied dxz and dyz orbitals, which has little effect on the
magnetic properties, while the temperature dependence of the magnetic
relaxation appears to have no correlation with the torsion angle.