Synchrotron X-ray Absorption Spectroscopy - Stanford Synchrotron ...

Octahedrally coordinated
metal atom
Energy
Ligand Field Splitting
Ligand atom
∆
d 2
z
Those d-orbitals with lobes
directed towards the ligand atoms
will possess higher energies than
those with lobes directed in
between the ligands.
d −
2 2
x y
d xy d d
xz
yz
The energy separation of the orbitals ∆ is known as the ligand field splitting
I. J. Pickering and G. N. George GEOL 498.3/898.3
1s→3d transitions of transition metal ions
The size of the ligand field splitting ∆ (remember this is an excited
state splitting) can tell us about the nature of the metal site.
I. J. Pickering and G. N. George GEOL 498.3/898.3
d −
2 2
x y
d 2
z
d xy d xz d yz
d −
2 2
x y
High-Spin vs. Low-Spin Ferrous
d 2
z
d xy d xz d yz
I. J. Pickering and G. N. George GEOL 498.3/898.3
e g
t2 g
e g
t2 g
∆
Low spin, R ion=0.92 Å
High spin, R ion=0.75 Å
Low-spin Fe 2+ occurs with larger ∆, and gives rise to one peak of
relatively increased intensity.