ligandveld

Ligandveld, or ligand field theory (LFT) in English, is a theoretical framework used to describe the electronic structure of coordination compounds, especially transition metal complexes. It analyzes how ligands, through donated electron pairs, interact with a central metal ion and how these interactions split the metal’s degenerate d-orbitals. LFT extends crystal field theory by incorporating covalent mixing between metal and ligand orbitals via a molecular orbital approach, providing a more complete account of bond character in many complexes.

The theory emphasizes geometry-driven orbital splitting. In common configurations such as octahedral, tetrahedral, and square planar, thedegenerate d-orbitals split into sets with different energies, quantified by parameters like Δo (octahedral) or Δt (tetrahedral). The magnitude of these splittings depends on the nature of the ligands, often summarized by the spectrochemical series, which orders ligands from weak to strong field in terms of the splitting they induce.

Ligandveld also explains spin states in transition metal complexes. If the crystal field splitting is large compared with electron pairing energy, low-spin configurations are favored; otherwise, high-spin states prevail. This has consequences for color, magnetism, and reactivity.

For more detailed analysis, ligand field theory uses concepts such as Tanabe–Sugano diagrams and Racah parameters to describe d-electron configurations and transitions. The theory aids in interpreting electronic spectra, magnetic properties, and the overall bonding in coordination chemistry, while bridging the gap between purely ionic crystal field models and covalent bonding perspectives.