Dear researchers,
Recently I've been conducting a research with diimmonium dye, a kind of NIR-absorptive organic dyes. I cannot easily find the reference papers related to this diimmonium moiety which containing useful information such as general synthetic procedure, or recommended purification methods. My product(and this diimmonium moiety) seems to be extremely labile, only few seconds of UV light on TLC plate change the color of the spot(pale yellowish-green to dark green).
My question is:
1. TLC analysis from crude reaction mixture showed that the major spot is the exact product what I desired, however, but the yield obtained after silica column chromatography was very low, below 10%. Eluent condition was DCM:MeOH = 50:1. It seems that adsorption of my products occurs on silica, so are there any tips to minimize the loss due to the adsorption? (Solubility in eluent is very good)
2.When I TLC analyze the 'freshly obtained' product (right after the column chromatograpy), there was no spot left on the baseline. But after I dry up the solvent and 're-analyze' it on TLC plate, the result changes, unsoluble spot remains on the baseline. My co-worker said that tertiary amine groups in diimmonium moiety are very unstable, and the oxidation of amine groups result in decomposition of dye.
So is there any methods to prevent the decomposition(or oxidation) of this diimmonium moiety?
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