In which symmetry groups do we typically observe the Jahn-Teller effect?

The Jahn-Teller effect is a geometric distortion of non-linear molecular systems, which occurs in certain symmetry groups when degenerate electronic states are present. This effect stabilizes the system by lowering its energy through the removal of the degeneracy.

Typically, we observe the Jahn-Teller effect in symmetry groups that feature degenerate orbitals or electronic states. The Oh symmetry (octahedral) is particularly relevant, as it contains degenerate t2g or eg orbitals in transition metal complexes. When such orbitals are occupied by electrons, distortion occurs to achieve lower energy configurations. Similarly, D4h symmetry has degenerate orbitals that can lead to the Jahn-Teller effect when electrons occupy these states. C4v symmetry can also exhibit this effect under certain conditions, especially in complexes with axial and equatorial positions leading to distortion.

Thus, option B — including symmetry groups C4v, D4h, and Oh — correctly identifies groups where the Jahn-Teller effect is commonly observed, as they encompass systems with degenerate states that can undergo distortion to achieve a more stable electronic configuration.