I want to purify such kind of 2,6-Bis(3-methylimidazol-1-ylidene)pyridine dibromide or 2PF6 salts via column chromatography. These dibromide salts are soluble in water and PF6 salt are soluble in acetonitrile. In this solubility condition which kinds of eluent, should perfectly work for column chromatography...?
One thing I would try is aqueous normal phase (aka HILIC). This can be done with silica, diol, or alumina packing. The weak solvent would be organic, miscible with water, such as THF, acetone, methanol, or acetonitrile (you mentioned the compound is soluble in acetonitrile, but maybe the compound has greater affinity for the packing than the solvent). You may want to run the column with an acidic modifier such as acetic acid, formic acid, or trifluoroacetic acid.
For column chromatography, I would dry-load the sample. I'd pack or equilibrate the column in 1-2% water, and run a gradient.
These links have more information:
http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN78_HILIC_Purification_Strategies_for_Flash_Chromatography.pdf
http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN84_RediSep_Rf_Gold_Silica_and_Highly_Polar_Solvents.pdf
http://www.isco.com/WebProductFiles/Applications/101/Poster_and_Paper_Reprints/Strategies_for_the_Flash_Purification_of_Highly_Polar_Compounds.pdf
Generally the best option for species of this sort is ion exchange given the high loading capacity of suitable ion exchange resins. Ion exchange resins can be operated in the presence of organic solvent although it's generally advisable to have at least some water in the mobile phase. Specifically what impurities are you trying to remove?
Dear Chris Pohl, thanks for answer. Actually There are four side products with my desired compound ( according to NMR) and each of them have similar basic unit. I want a particular and specific compound having basic unit. 2,6-dibromo, 4-chloropyridine is basic unit and i have substituted both Br with 1-methylimidazole unit. But in product contains many substituted compounds.
It should be feasible to resolve such compounds via ion exchange but it will require a small particle size material and solvent in the mobile phase.
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