Spectrochemical Series
Definition and meaning of Spectrochemical Series in chemistry.
The spectrochemical series is an established list of chemical ligands ordered by their specific ability to split the d-orbital energy levels of a central metal ion in a coordination complex.
In more detail
Ligands located at the lower end of the series, such as the iodide ion (I-), produce a relatively small splitting of the d-orbitals and are designated as weak-field ligands. These typically form high-spin chemical complexes. Conversely, ligands positioned at the upper end, like carbon monoxide (CO) or the cyanide ion (CN-), cause a massive energy splitting and are called strong-field ligands, often leading to low-spin complexes. This orbital energy splitting directly dictates the magnetic properties of the complex and determines the exact visible colors of light it absorbs and emits.
Key facts
| Field | Inorganic Chemistry |
|---|---|
| Weakest Ligands | Halides like I- and Br- |
| Strongest Ligands | CO, CN- |
| Effect | Determines d-orbital splitting energy |
The cyanide ion (CN-) sits very high on the spectrochemical series and acts as a strong-field ligand, whereas the chloride ion (Cl-) sits much lower as a weak-field ligand.
Frequently asked questions
How does the spectrochemical series relate to the color of a coordination complex?
The ligand field strength determines the energy gap between d-orbitals. This gap corresponds to the specific wavelength of light absorbed, which then dictates the complementary color that is visually observed.