phthalocyanine

And finally, beautiful, fluffy crystals at the bottom of my flask! Great!

Purification of organic compound could be done on several ways, the most popular nowdays is chromatography, which is quite practical, but requires often a LOT solvent. Other methods include distillation what is a great method if the compound could be vaporized at room or diminished pressure and of course there is crystallization. 

Crystallization could be a highly complex problem if quite similar compounds are in the raw product and often several crystallizations should be made from different solvents to obtain a pure product, so crystallization is often stated as an art, but if it’s successfully done, it could afford perfectly pure products. 

Long ago a prof at the department recrystallized 1 g of a phthalocyanine dye from 1 liter of concentrated (95%) sulfuric acid. Hard to imagine, but it gave a pure product and the compound was isolated in a good yield.

Something interesting: a classical demonstration in fluorous chemistry: 3 non miscible layers (organic-aqueous -fluorous).

The upper layer is an organic solution: Sudan IV (a red colored azo dye) dissolved in toluene.

The middle layer is water and methanol.

The bottom layer is a fluorous solution: perfluoroalkylated cobalt phthalocyanine (a blue colored complex) dissolved in perfluoroperhydrophenanthrene.