Laporte rules and crystal field stabilisation energies Flashcards
What is Laporte’s rule?
If a system is centro-symmetric, transitions between states with the same inversion symmetry are forbidden, but transitions between states of different inversion symmetry are allowed
What is a transition between states of the same inversion symmetry?
G -> G
U -> U
What is a transition between states of different inversion symmetry?
G -> U
What does centrosymmetric mean?
You can pass through each ligand and it gives you the same molecule
What is the spin multiplicity rule?
Transitions between states with different spin multiplicities are forbidden
Which complexes have transitions which are laporte forbidden and why?
Transitions of octahedral and square planar complexes
All of the D orbitals are gerade
What makes the d-d transitions vibronically allowed?
The vibration-induced breakdown of the laporte Rule
What does static loss of centrosymmetry have the same effect as?
Breaking the laporte rule
What results in a small departure from centrosymmetry?
Vibronic or static distortion
Why are d-d transitions for tetrahedral complexes Laporte allowed?
They have no inversion symmetry
What is the middle of the two energy levels called?
Barycentre
What does CFSE stand for?
Crystal field stabilisation energy
What is CFSE?
Net energy of the t2gˣegʸ configuration relative to the average energy of the unperturbed orbitals
What is added to calculate CFSE for each electron in the eg energy level?
+0.6 ΔO
What is added to calculate CFSE for each electron in the t2g energy level?
-O.4 ΔO
