crystal field theory

Crystal field theory (CFT) is a model used in chemistry to explain the electronic structure of coordination compounds, particularly those involving transition metals. It treats the bond between a central metal ion and surrounding ligands as primarily ionic. In CFT, ligands are represented as point charges that create an electrical field, influencing the energy of the metal ion's d orbitals.123

In an isolated metal ion, the five d orbitals have the same energy. However, in the presence of ligands, these orbitals split into different energy levels. For example, in an octahedral arrangement, the d orbitals split into two groups: a lower-energy set (t_2g) and a higher-energy set (e_g). The energy difference between these sets is called the crystal field splitting energy (CFSE). This splitting helps explain the magnetic, spectroscopic, and thermodynamic properties of transition metal complexes. Ligand field theory (LFT) is a more advanced version that incorporates some covalent character into the metal-ligand bond.132