[kims]

Cr3+ is supposed to be blue-green, why is it brown. Do you know what other structure is produced containing the phenol? The phenol was eugenol btw. I read somewhere that unsubstituted phenols give brown but in this case it is not unsubstituted. Thanks!

[ARGOS++]

Dear Dakims;

In the case of Eugenol for a color influence only the Methoxy- group is of relevance and counts in ortho position with 7 till 15nm. Such a small change the eye is not able to detect.

Much more important is therefore that the “Phenolate” Ion has a big influence (enlarging the chromophor) of the basic color. As Crⁿ⁺  similar as Moⁿ⁺ can coordinate till (as I know) 8 Ligands, the finally brown (a very unspecific color! – a very, very broad absorption) is easily indicated.
But for all possible Coordination Numbers you must ask good specialists in Coordination Chemistry.
I can also not “calculate” how stabile the “Phenolate” Ion against oxidation (on air) will be in such a complex, because that would even more shift/broaden the absorption too.

You may also study the following reference:     "Complex (chemistry)”

Good Luck!
                   ARGOS⁺⁺