Why is potassium permanganate coloured?

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SUMMARY

Potassium permanganate, chromate, and dichromate exhibit color due to ligand-to-metal charge transfer (LMCT) processes. In these cases, oxygen atoms donate electrons to the empty d orbitals of manganese in the +7 oxidation state and chromium in the +6 oxidation state, despite both being classified as d0 ions. This electron transfer allows these compounds to absorb visible spectrum radiation, resulting in their characteristic colors. The discussion highlights the importance of understanding LMCT in explaining the coloration of these compounds.

PREREQUISITES
  • Understanding of oxidation states, specifically +7 for manganese and +6 for chromium.
  • Familiarity with d orbital electron configurations in transition metals.
  • Knowledge of ligand-to-metal charge transfer (LMCT) processes.
  • Basic principles of electronic spectroscopy.
NEXT STEPS
  • Research "ligand-to-metal charge transfer (LMCT) in transition metal complexes."
  • Study "electronic spectroscopy of transition metals" for deeper insights.
  • Explore "oxidation states and their effects on color in coordination compounds."
  • Investigate "the role of ligands in determining the properties of transition metal complexes."
USEFUL FOR

Chemistry students, researchers in inorganic chemistry, and professionals studying transition metal complexes and their optical properties will benefit from this discussion.

CrimpJiggler
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In the permanganate ion, manganese is in the +7 oxidation state, therefore it is a d0 ion. I thought that d0 and d10 ions don't absorb visible spectrum radiation because there are no electrons to jump to higher crystal field orbitals (or in the case of d10 ions, there are no free orbitals for electrons to jump to). I remember reading months ago an explanation for this that involved something to do with the ligand donating electrons into Mn(VII)s empty d orbitals. Can anyone explain this to me?

EDIT: Also I'd like to know why chromate is coloured. Again Cr(VI) is a d0 ion, therefore its not absorbing radiation due to electrons jumping to higher orbitals in the crystal field. What is causing it to absorb visible radiation?

UPDATE: I found out the answer to this question. Permanganate, chromate and dichromate are coloured for the same reason. Ligand to metal charge transfers. In each case, oxygen transfers electrons to the empty d orbitals on the metal atom. Interesting stuff, I found this info here:
http://www.webexhibits.org/causesofcolor/8.html
 
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