Dear C.C. Lu,

According to the lab of M.G. Finn, THPTA is superior to TBTA in aqueous systems in terms of observed reaction rates and protection towards air. If you are interested in Cu-catalyzed alkyne-azide cycloaddition in aqueous media, there are also other ligands around from Peng Wu's lab and procedures from Ben Davis.

Unfortunately I don't have any hard data available to answer your second question. However, I would recommend that you store them seperately in small volume stock solutions. It worked fine for me and it seems they are fine in the freezer nearly indefinitely. And it's not to much afford to mix them prior to use.

I hope that helped.

Cheers,

Lukas

PS: If you like I can also forward you links to some of the papers.

Dear Lukas,

It' s very kind of you for your answers.  

My job is to develop a novel chemical probe and Cu-catalyzed alkyne-azide cycloaddition is used during the synthesis steps.  So, I prefer a  Cu(I)-stabilizing ligand that has a high efficiency and can be purchased.

Would you give me the paper link of M.G. Finnthat you mentioned. Thank you so much.

Congcong

Usually for this type of reaction, the Cu(II)SO4 is reduced in situ to Cu(I) with sodium ascorbate first before running click reaction. If you store the Cu(II)SO4 THPTA solution by itself it should have a very long shelf life, then when you need to run the reaction, aliquot out the appropriate volume and add sodium ascorbate to generate the catalytically active Cu(I).  If the ligand is good like you say at protecting the copper from oxidation/disproportionation, then the Cu(I) should stay active for the lifetime of your experiment as long as argon lines, degassed solvents, and proper schlenck technique are used.

So I recommend storing it as a Cu(II)/THPTA solution, and when you need some to run your reaction, remove the appropriate volume and add the correct amount of sodium ascorbate

Will Cu(II)/THPTA solution be stable enough when stored at room temperature?

Sure, I don't see any problem storing it as the Cu(II) solution.  But I don't quite understand why you wouldn't just all store the reagents individually as solids and add them as such whenever you need to run the reaction.  Storing everything as solids will have a much longer shelf life than storing it as a solution.

Dear Roscoe

No more than 10 μl Cu/TBTA (10 mM) solution needed for each reaction  in my system. So, it can not be prepared freshly each time and TBTA is also expensive.

Thank you very much for your suggestions. Good luck to your research.

What would be the ideal solution to solubilize TBTA??

DMSO works well, TBTA/CuSO4 is soluble in DMSO/water mixture 1:1 v/v;

Sometimes it precipitates after addition of aqueous ascorbate - then it is necessary to add more DMSO 

Please check out this one 

http://www.glenresearch.com/GlenReports/GR26-15.html

There is difference in reactive, THPTA seems to work much better under almost all conditions compared to TBTA. The difference might be due to solubility. In our hands TBTA was a bit troublesome to work with  in close to aqueous media, too much of precipitation. 

There a few others very efficient Cu chelators that came from Dr. Peng Wu lab.

http://pubs.acs.org/doi/abs/10.1021/ja106553e

http://onlinelibrary.wiley.com/doi/10.1002/anie.201101817/abstract

http://onlinelibrary.wiley.com/doi/10.1002/anie.201108181/abstract

All chelators are commercially available at

https://clickchemistrytools.com/product-category/click-chemistry-toolbox/click-chemistry-toolbox-auxiliary-reagents/