JahnTellerilmiö

The Jahn-Teller effect is a geometric distortion of a molecule or crystal that occurs when it has a degenerate electronic state. Degeneracy means that there are multiple electronic states with the same energy. The Jahn-Teller theorem states that any non-linear molecule with a degenerate electronic state will undergo a geometrical distortion that lowers its symmetry and lifts the degeneracy. This distortion results in a lower overall energy for the system.

This effect is significant in inorganic chemistry, particularly in the study of transition metal complexes. When a transition metal ion is in a high-spin d orbital configuration that leads to electronic degeneracy, the surrounding ligands will arrange themselves in a way that is not perfectly symmetrical. For example, in an octahedral complex, the metal-ligand bonds might elongate or shorten along certain axes. This dynamic rearrangement minimizes the electronic repulsion and stabilizes the molecule.

The Jahn-Teller effect can influence various properties of materials, including their optical absorption spectra, magnetic behavior, and catalytic activity. The extent of the distortion depends on the specific electronic configuration and the strength of the interactions between the metal ion and its ligands. While the effect is often discussed in terms of static distortions, dynamic distortions where the system rapidly fluctuates between different distorted geometries can also occur. Understanding the Jahn-Teller effect is crucial for predicting and explaining the behavior of many transition metal compounds and materials.