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My book(Page $259$ section $9.5.5$) says that the color mainly comes from absorption of light in the coordination compound:

The color is complementary of the wavelength it absorbs , the wavelength left over is the color of the complex.

But there are two instances of these coordination complexes: $\ce{[Co(NH3)5(H2O)]^{3+}}$ which absorbs blue green light of wavelength $\pu{500nm}$ which appears to be red in color and

$\ce{[Ti(H2O)6]^{3+}}$ which absorbs blue green light of wavelength $\pu{498nm}$ which appears to be violet in color.

Question: If a color of a complex is determined with what color it absorbs then why is it that two complex's have the same absorption region yet appear to be in different colours

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    $\begingroup$ As you can see here, wavelengths of the maximum absorption says nothing about the shape and width of very broad absorption bands, typical for condensed phases. Thin absorption lines are seen (almost(?)) exclusively for atomic absorption spectra in gaseous phase only. $\endgroup$
    – Poutnik
    Commented Sep 23, 2023 at 7:44
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    $\begingroup$ When we see the colour, the way we perceive it is very complicated, it depends somehow on how much is absorbed vs reflected at many wavelengths. But, in practise to characterise molecules we use a spectrophotometer and measure exactly what the absorption is vs. wavelength. This enables us to work out where the energy levels in the molecule are. $\endgroup$
    – porphyrin
    Commented Sep 23, 2023 at 14:25
  • $\begingroup$ @porphyrin oh okay , then we can say titanium complex is having stronger reflection of violet light and strong absorption of blue green and , for the cobalt complex strong absorption of blue green and stronger reflection of red ? $\endgroup$
    – Razz
    Commented Sep 24, 2023 at 2:08
  • $\begingroup$ @Poutnik thank you , it seems the materials absorb a range of wavelengths which makes them recieve their characteristic colour $\endgroup$
    – Razz
    Commented Sep 24, 2023 at 2:09
  • $\begingroup$ As I mentioned the way we perceive is complex, a solid of the same substance may appear quiet different to its dilute solution hence the use of instruments to characterise. I have seen a 'color wheel' that helps one to understand absorption/reflection and what you actually see, you could search or possibly someone else has a reference. $\endgroup$
    – porphyrin
    Commented Sep 24, 2023 at 7:29

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