Dear colleagues,
I received this question from a reviewer:
Among different metal ions and anions, why Question: the chemosensor exhibit high selectivity towards Cr3+ only?
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The chemosensor I used to detect Cr3+ ion is a Schiff-base, and to the best of my knowledge, the related papers do not explain clearly the reason why a molecule is a selective sensor towards a specific ion.
So, my response the following:
"The sensing mechanism and selectivity towards Cr3+ can be supported by computational calculations, which estimate the sensing capability of molecules mainly basing on intermolecular interactions and compatibility between ion size and the geometry of chelating site. Hence, the selectivity observed for Cr3+ ion can be explained by its interactional and geometrical affinity to the chelating site."
Despite our response, we received a second revision in which reviewer is asking the same question!
Anyone can help me please!
Waiting for your responses.
With Thanks
Dear Achref,
Because the chromium ion has a triple positive charge, it is possible that this, combined with other factors such as binding site geometry and chromium ion size, may favour probe interaction with the chromium. You can also look at how many interaction sites are required for strong chromium ion binding. You need to see what is different about chromium ions from other ions that allow their interactions with the probe. Hope it will work for you
The HSAB principle also plays a crucial role here. Cr3+ being a hard acid tends to bind stronger to the hard centers in the schiff base ligand due to hard-hard interaction.
Moreover, the cavity size produced by the ligand for the host-guest interactions is ideal for Cr3+ ion to strongly bind with the ligand. For other ions, the cavity size may not be suitable for the interaction to take place as that of Cr3+.
It can be explained by HSAB principle as well as sensing is an inherent property of a ligand or schiff base, it depends on charge, radius, charge density etc.
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