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Background: we were doing Crystal Field Theory in school when this question popped up. Specifically we were talking about stability obtained due to the chelate effect and if the extra stability in a complex would affect the wavelength of light it absorbed.

The exact question is:

Arrange in decreasing order of wavelength of light absorbed:
$\ce{[Fe(ox)3]}$, $\ce{[Fe(CN)6]^{3-}}$ and $\ce{[Fe(H2O)6]^{3+}}$

If we considered wavelength depending on stability, the answer differed than if we consider splitting only.

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    $\begingroup$ The more the ligand splits the $t_{2g}$ and $e_g$ levels (often called $10 D_q$ or $\Delta_0$) the shorter the wavelength of light absorbed. The size of $D_0$ is related to the position in the (experimentally determined) spectro-chemical series. Look up the order of ligands in this series and you have your answer. $\endgroup$
    – porphyrin
    Commented Apr 26, 2018 at 18:20
  • $\begingroup$ The spectrochemical series we have done does not account for Chelsie effect. My question is if the effect will change the wavelength of light absorbed compared to the wavelength it should based on the spectrochemical series $\endgroup$
    – Shivay Vadhera
    Commented Apr 27, 2018 at 0:07
  • $\begingroup$ I think the stability achieved due to chelating effect is already accounted for in the spectrochemical series, so that series can be used as a correct basis for deciding the wavelength absorbed by the complex. $\endgroup$
    – Sathvik Reddy
    Commented Jul 1, 2022 at 9:11

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