JAHN-TELLER EFFECT

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JAHN-TELLER EFFECT :

JAHN-TELLER EFFECT Introduction, theorem, tetragonal distortion

INTRODUCTION :

INTRODUCTION In 1937 Jahn and Teller put forward a theorem known as Jahn –Teller theorem. This explain why certain 6 coordinated complexes undergo distortion to assume distorted octahedral (i.e. tetragonal) geometry.

REGULAR OCTAHEDRAL COMPLEXES :

REGULAR OCTAHEDRAL COMPLEXES The 6 coordinated complexes in which all the 6 distances between the ligand and metal are equal are said to be regular /symmetrical octahedral complexes

DISTORTED OCTAHEDRAL COMPLEXES :

DISTORTED OCTAHEDRAL COMPLEXES The 6 coordinated complexes in which all the 6 distances between the ligand and metal are not equal are said to be distorted octahedral complexes

JAHN TELLER THEOREM :

JAHN TELLER THEOREM Any non liner molecular system possessing degenerated electronic state will be unstable and will undergo distortion to form a system of lower symmetry and lower energy and thus will remove degeneracy

Z-OUT DISTORTION

Z-IN DISTORTION

SYMMETRICAL AND UNSYMMETRICAL t2g :

SYMMETRICAL AND UNSYMMETRICAL t2g The symmetrical t2g orbitals are t2g0, t2g3, t2g6 The unsymmetrical t2g orbitals are t2g 1,t2g 2,t2g4, t2g5

SYMMETRICAL AND UNSYMMETRICAL eg ORBITALS :

SYMMETRICAL AND UNSYMMETRICAL eg ORBITALS The symmetrical eg orbitals are eg0, eg4, The unsymmetrical eg orbitals are eg1, eg3 The eg2 orbital is symmetrical when configuration is (dx2-y2)1(dz2)1and unsymmetrical when configuration is (dx2-y2)0(dz2)2

Slide 11:

t2g(sym)+eg(sym)=No Distortion t2g(unsym)=Slight Distortion eg(unsym)=Strong Distortion