TRANSITION METALS E x p l a i n i n g c o l o u r

TRANSITION METALSExplaining colour

Using the key words: Absorbed, transmitted and reflected explain the colours in each of the following:

MnCl2 FeCl2

FeCl2 FeCl3

FeCl3 Fe(NO3)3

Use these 6 pictures to work out the three factors that affect the colour of a transition metal compound…

MnCl2 FeCl2

FeCl2 FeCl3

FeCl3 Fe(NO3)3

Use these 6 pictures to work out the three factors that affect the colour of a transition metal compound…

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

2NH3 4NH3

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG BG

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG B

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG B

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG B

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG B

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG B

Describe what happens to the average frequency of visible light absorbed as you increase the number of NH3 ligands…

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG B

Describe what happens to the average frequency of visible light absorbed as you increase the number of NH3 ligands…

[Cu(H2O)6]2+(aq) [Cu(OH)2(H2O)4](s) [Cu(NH3)4(H2O)2]2+(aq)

Explaining the colour-ligand relationship

RBG

RBG BG B

Describe what happens to the average frequency of visible light absorbed as you increase the number of NH3 ligands…

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

Ligand field theory

Ligand field theory

The negative charge due to the lone pair affects the orbitals energy differently

Ligand field theory

The negative charge due to the lone pair affects the orbitals energy differentlyWhen ligands approach orbitals that have lobes along the axes the energy is raised

Ligand field theory

The negative charge due to the lone pair affects the orbitals energy differentlyWhen ligands approach orbitals that have lobes along the axes the energy is raised

Ligand field theory

The negative charge due to the lone pair affects the orbitals energy differentlyWhen ligands approach orbitals that have lobes along the axes the energy is raised When ligands approach orbitals that have lobes between the axes the energy is lowered

Ligand field theory

The negative charge due to the lone pair affects the orbitals energy differentlyWhen ligands approach orbitals that have lobes along the axes the energy is raised When ligands approach orbitals that have lobes between the axes the energy is lowered

SUMMARY• When the 5 d-orbitals are free of ligands they are of equal energy

(degenerate)• When the d-orbitals are surrounded by ligands the energy is split.• Two orbitals are higher in energy and three orbitals are lower.

Ligand field theory

The negative charge due to the lone pair affects the orbitals energy differentlyWhen ligands approach orbitals that have lobes along the axes the energy is raised When ligands approach orbitals that have lobes between the axes the energy is lowered

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

What is the electron configuration of a Cu2+

ion? (spdf notation)

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

Ammonia is a stronger base that water. Predict the effect that this will have on the energy difference between the spit orbitals…

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

What happens next? Many sources explain that the electron de-excites and re-emits light. The problem with this is that the same frequency of light would be emitted as was absorbed in the first place and no net absorption would take place so the compound would be colourless. Other mechanisms of de-excitation are being investigated such as collisional de excitation

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

Ener

gy

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

Ener

gy

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

Absorbed low frequency Absorbed high frequency

The average frequency of visible light absorbed INCREASES when you substitute H2O ligands with NH3 ligands.

Absorbed low frequency Absorbed high frequency

General rule of colour of aqueous octahedral complexes

The more ligand molecules that are stronger lewis basesThe colour shifts towards the high frequency / high energy end of the spectrum

Example question