Topic 15: Coloured complexes

Describe how transition metal complexes are different colours?

Ligand causes d-orbitals to split into 2 energy levels -> electrons absorb light energy from visible region → electrons promoted to higher d orbitals -> colour seen will be transmitted while the colour complementary to it will be absorbed

What are factors that can affect the colour of a transition metal complexs?

• Type of ligands

• Shape of ligands

• Oxidation state of the central metal ions

• Coordination number

• Number of electron in d-subshell

How do these factors affect colour?

Changes size of energy gap between d-orbitals -> changes frequency of visible light absorbed

Why are some complexes white or colourless?

Full or empty d-subshells means no electrons will move to higher energy levels -> hence complexes = white/colourless