Is there any method available to determine the binding stoichiometry between a metal and a ligand, if the molecular weight of the ligand is not known? I know about job's plot and mole ratio method but for the job's plot or mole ratio method one need to know the molecular weight of both the cation and anion. But I do not know the molecular weight of the ligand as it it is a natural product. So I am unable to find the binding stoichiometry whether it is 1:1 or 1:2 or anything else. If anyone have any idea about it please help me to solve this issue.
Hi Subhadeep, Thank you for your interesting question.
If sufficient amounts of the sample are available, wet chemical methods such as titration or gravimetry are still a good choice. Often these methods are forgotten or dismissed as antiquated, even though they can be used to perform very accurate analyses under the right conditions. Most methods can be designed as microanalysis for very small sample quantities. However, a sample quantity of approx. 100 mg should be available for each analysis. Of course, this depends in detail on the compound in question.
For most metals, for example, complexometric titration with EDTA is an option, and many ligands can also be specifically determined due to their donor property.
For example, I myself checked the stoichiometry of my europium complexes in my doctoral thesis using a titrimetric method.
Hopefully my answer can help you. I wish you much success in your research.
Florian Morsbach Thank you for your suggestion but the problem is the natural compound I am talking about is not in pure form rather it is the crude one, i.e., mixture of many compounds may be present there. I know the molecular weight of the metal as it is known but the problem arise for the ligand (the natural product extract).
