I always have the problem of finding whether a complex has colour due d-d transition of electrons or if it is due to electron exchange. Is there a general way to tell whether a complex has d-d transition or electron exchange? Is it the right method to check if a metal has d electrons and if it does. Its color must come from d-d transition and if not the color must come from charge transfer?

  • $\begingroup$ By electron exchange do you mean electron transfer of the form Fe(II) to Fe(III) for example? $\endgroup$ – porphyrin Apr 24 '17 at 9:28
  • $\begingroup$ No.. From metal to ligand or from ligand to metal. $\endgroup$ – Lakshya Gupta Apr 24 '17 at 9:35
  • $\begingroup$ That's usually called "charge transfer" not "electron exchange" en.wikipedia.org/wiki/… $\endgroup$ – orthocresol Apr 24 '17 at 10:10
  • $\begingroup$ in which case d-d transitions are usually weak and at long wavelength, metal-ligand transitions are usually more intense and may swamp d-d in some cases. But there is no hard and fast rule, you have to study each case carefully. $\endgroup$ – porphyrin Apr 24 '17 at 10:58
  • $\begingroup$ So if I'm given a complex compound. I would have to check if it has d-electrons or not and find out if d-d transition is taking place? $\endgroup$ – Lakshya Gupta Apr 24 '17 at 14:04