Hi Nishu Choudhary , this is how I did it recently.

Article Copper-Induced Fluorescence Quenching in a Bis[2-(2′-hydroxy...

Hop this help.

Chathura Abeywickrama

Sir, this is for 1:1 M:L(metal to ligand) binding. The compound that I have synthesized is showing 2:2 M:L binding forming M2L2 complex. So, could you suggest any method by which I can calculate binding constant for 2:2 binding model using fluorescence titration?

Hi Nishu Choudhary,

you could give SupraFit a try:

https://github.com/conradhuebler/SupraFit/releases/tag/2.5.118

In case of a not complicated fluorescence mechanism, which allows applying uv/vis models, the recent SupraFit version can be used with a model of flexibel stoichiometry.

If there are any questions and problems with the program, feel free to ask.

Conrad Hübler

Thanks for the information. But, Suprafit version is also for 1:1, 1:2 & 2:1 model only. Is there any method where I can calculate the binding constant for 2:2 model using fluorescence titration data?

It is correct, that the special fluorescence models do not have the one model with flexible stoichiometry. However, if there is no advantage of the fluorescence model over the general uv/vis one, than the uv/vis models should be sufficient.

So, if you were fine with the models (apart from the stoichiometry) on supramolecular.org, which are the uv/vis models, than you can go with the uv/vis models in SupraFit and use the flexible model.

Then, set A = 2 and B = 2 as highest equivalents and uncheck all these species, which are not of interest.

If however, there is a more complicated fluorescence mechanism present, SupraFit would also not be helpful right now. I have not enough knowledge of the possible processes. But I am open for input and test cases :-)

Regards,

Conrad