JAHN- TELLAR EFFECT It was stated by Jahn and Teller that any non –linear molecular system in orbitally degenerate electronic state (i.e., a state which represents more than one electronic arrangement of the same energy) would be unstable and that it would get stabilised by undergoing distortion in its geometry and thus by causing a split in its orbitally degenerate electronic state. The above statement is known as Jahn-Tellar effect. The distortion in the geometry of the non-linear molecular system thus produced is known as Jahn-Tellar distortion. The lowering of symmetry of the non-linear system due to Jahn –Tellar effect always occurs in a manner which results in decrease in the energy of the system. Let us consider an octahedral complex of Cu +2 with unidentate ligands L - . The Cu +2 ion in a perfect octahedral ligand environment has the ground state electronic configuration t 6 2g e 3 g which represents two electronic arrangements t 6 2g d 2 z 2 d 1 x 2 -y 2 of equal ...