Topic 8: Crystal Field Theory Part 1

Decrease apart from Mn and Zn

Decrease apart from Mn and Zn

A very simple ionic model which rationalises colour and magnetism (an electrostatic model)

A more complex, comprehensive bonding theory. Allows consideration of both covalent and ionic contributions

dxy dxz dyz (lobes point between axis) dx^2-y^2 dz^2 (lobes point along axis)

The metal is treated as a positive point charge (M^+) and the ligands as negative point charges (:L^-) which donates an electron pair

degenerate same repulsion of electrons in d-orbitals, causing them to increase in energy

eg: dx^2-y^2 dz^2 increases in energy by 3/5 Delta O relative to barycentre (destabilised), direct overlap with axis t2g: dxy dxz dyz deceases in energy by 2/5 Delta O relative to barycentre (stabilised), no direct overlap with axis

Centre of gravity for splitting of d-orbitals 0 reference point (energy in spherical field)

Delta O in octahedral Delta T in tetrahedral

t2: dxy dxz dyz increases in energy by 2/5 Delta T relative to barycentre (destabilised), orbitals interact more strongly with ligands e: dx^2-y^2 dz^2 deceases in energy by 3/5 Delta T relative to barycentre (stabilised), orbitals interact less strongly with ligands

much larger 6 ligands rather than 4 so more stabilisation and destabilisation In delta O, ligands point directly at orbitals, don’t in delta T

low spin delta O > P high spin high spin P always > delta T

Send an electron from t2g to eg and calculate how much energy is required (how much light is absorbed)

E = hc v bar x NA

increases closer to metal interacts more with d-orbitals

large energy split in their d-orbitals small split