KMnO 4 is coloured due to:
- d-d transitions
- charge transfer from ligand to metal
- unpaired electrons in d orbital of Mn
- charge transfer from metal to ligand
b. charge transfer from ligand to metal
The Mn atom in KMnO4 has +7 oxidation state with electron configuration [Ar]3d 0 4s 0 Since no unpaired electrons are present, d−d transitions are not possible. The molecule should, therefore, be colourless.
Its intense purple due to L→M (ligand to metal) charge transfer 2p(L) of O to 3d(M) of Mn.