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Colour and the d block

Colour and the d block. UV / Vis frequencies are have photons with energies of the sort of values needed to promote electrons from their ground state energy level to a higher level. A typical substance will require UV photons so does not absorb Visible light. Most substances are colourless. .

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Colour and the d block

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  1. Colour and the d block

  2. UV / Vis frequencies are have photons with energies of the sort of values needed to promote electrons from their ground state energy level to a higher level. • A typical substance will require UV photons so does not absorb Visible light. • Most substances are colourless.

  3. d – block metal complexes • These have unusually close energy levels due to the splitting of the 3d orbitals in a non spherical environment.

  4. 3d orbitals in gas Energy

  5. But in an octahedral complex two of the orbitals will be closer to ligands than the other three. But ligands usually have a negative charge… ..so electrons in the d orbitals are repelled. They have a higher energy

  6. 3d orbitals in complex Energy Closer to ligands Further from ligands

  7. d electrons will tend to go preferentially into the lower energy orbitals further from the ligands. Ti has the electron configuration [Ar] 3d2 4s2 So Ti3+ has the electron configuration [Ar] 3d1

  8. 3d orbitals in Ti3+ complex Energy

  9. 3d orbitals in Ti3+ complex Absorbs a photon of yellow light Energy

  10. So what d block complexes will not be coloured ? Ones with no d electrons eg…… Sc 3+, Ti 4+ ..or those for which the d shell is full so electrons cannot move. Eg… Zn2+ , Cu+

  11. 3d orbitals in Cu+ complex Energy

  12. Different ligands cause different degrees of splitting of the d orbital energies. Ligand exchange therefore usually causes a change of colour

  13. 3d orbitals in Ni2+ complexes Absorbs orange appears blue Absorbs red appears green Ni(H2O)62+ Ni(NH3)62+

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