Crystal field splitting is the splitting of the d-orbitals in a transition metal ion when ligands approach and form a complex. Here’s a explanation:
1. Why splitting happens
- In a free metal ion, all five d-orbitals have the same energy.
- When ligands approach the metal, their electron clouds repel the d-electrons.
- This repulsion causes the d-orbitals to split into groups with different energies.
2. Octahedral complexes (common case)
- Six ligands approach the metal along the x, y, and z axes.
- The d-orbitals split into two sets:
- Higher energy (eg): dz² and dx²−y² (point directly at ligands → more repulsion)
- Lower energy (t2g): dxy, dxz, dyz (point between ligands → less repulsion)
3. Consequences of crystal field splitting
- Determines whether a complex is high-spin or low-spin.
- Affects the color of the complex (d-d electron transitions absorb light).
- Influences the magnetic properties of the complex.
In short:
Crystal field splitting is the energy difference that occurs when d-orbitals of a metal split due to the presence of ligands, and it explains the color, magnetism, and spin state of transition metal complexes.