Sciencemadness Discussion Board

Copper Phthalocyanine preparation

Mephisto - 9-11-2005 at 12:46

In this thread I want to present me results and encourage to the preparation of copper phthalocyanine, as it may be fun for everyone who is interested in dyes and pigments. Even if the structure of copper phthalocyanine looks difficult on the first view, I am sure most (amateur) chemists here will be able to synthesize it at home.


The structure of this metal-complex pigment reminds of the porphine-structure of natural colourings like haemin and chlorophyll. Compared to these natural products, the synthetic phthalocyanine is extremely stable against chemicals and high temperatures. For example: it can be sublimated without decomposition at about 580 °C in low pressure inert atmosphere. Therefore it is used nowadays to colour thermoplastics.

There are different methods to synthesize copper phthalocyanine; I want to recommend the variation with urea, copper(II)-chloride, phthalic acid and ammonium molybdate as educts, because it is the easiest way. I have done it as follows.

5 g phthalic acid, 1 g copper(II)-chloride, 25 g urea and around 50 mg ammonium molybdate as catalyst were thoroughly ground together in a mortar. The mixture was heated 6 hours at 180 °C on a heating bath. During this time the colour changed from slight turquoise over blue to almost black. After this the crude product was boiled in 10% hydrochloric acid for 5 hours. After sucking out the blue pigment, it was suspended in 2 molar NaOH solution. 10 minutes later the mixture was again vacuum filtered. The copper phthalocyanine was boiled a second time in hydrochloric acid, sucked out and washed in the Buchner funnel with water to remove chloride ions. The yield is about 3-4 g of copper phthalocyanine.

I also made some digital photos while trying out that preparation.


The preparation is described in German language at (direct link to the synthesis). The photos there could be enlarged to a resolution of 1024x768 pixels by clicking on them.

I hope this was interesting for someone.


chemoleo - 9-11-2005 at 13:01

Very interesting!

Do you have EDTA? I'd be interested to see whether it is able to rip out the Cu (the colour change should be obvious, but do check Cu2+ in the presence of EDTA on its own). Alternatively, what happens if you i.e. add lots of NaOH? or Na2CO3? Is it stable under those conditions, is the complexing strong enough to hold on to the Cu?

With the uncomplexed form, I wonder what colour varieties can be produced. Examples are Mn2+, Co2+, Ni2+, Zn2+, Fe2+, etc.

Is there an OTC source for phtalic acid?

Mephisto - 9-11-2005 at 13:48

I don't have ETDA at home. The filtrate from the NaOH-washing was yellow, but I don't think the literature tells without a reason to suspend the product only for 10 minutes in the cold in NaOH solution.

> With the uncomplexed form, I wonder what colour varieties can be produced.
> Examples are Mn2+, Co2+, Ni2+, Zn2+, Fe2+, etc.

The Co2+ complex is also used by the industry. Until now I didn't find a nice comparison of possible metal-complexes. There is a Journal, which deals only with this topic (Journal of Porphyrins and Phthalocyanines), but mostly with very complex porphyrine structures. Because I am interested in your question too, I will do some further research in my free-time.

> Is there an OTC source for phtalic acid?

Unfortunately, no. Some people who have an old Kosmos chemistry-kit in the basement (you too chemoleo? ;)) will be happy, because there is some phthalic acid and a working ammonium molybdate salt in it. Somewhere I read succinimide forms analogue tetraazoporphines, but it isn't OTC too.

Another interesting thing would be to try out the preparation without ammonium molybdate in a microwave oven (see Tetrahedron 61, 2005, 179-188 - "Improvement in the synthesis of metallophthalocyanines using microwave irradiation";). But I am not sure if this can be done without overheating in a household microwave oven. If some is interested in this article, I will attach it here.


12AX7 - 9-11-2005 at 13:55

Interesting, colorful prep :)

Considering all the imines, doesn't the HCl wash make an HCl-salt with it?


Mephisto - 10-11-2005 at 13:37

Ullmann's Encyclopedia has much information about phthalocyanines. After this reading, I want to make a short quote related to the questions above.

Quotation from Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2002 Electronic Release
Phthalocyanine forms complexes with numerous metals of the periodic table. Today, 66 complexes with various elements are known. Metal phthalocyanines and compounds with metalloids such as B, Si, Ge, and As or nonmetals such as P display a wide variety in their coordination chemistry.
Phthalocyanines absorb strongly in the visible range of 600 to 700 nm. They are thus blue to bluegreen colorants.
Phthalocyanine and its unsubstituted metal derivatives dissolve in highly acidic media such as concentrated sulfuric acid, chlorosulfuric acid, or anhydrous hydrofluoric acid, presumably due to
protonation of the bridging nitrogen atoms. In the presence of strong bases, reversible deprotonation of the central imino groups occurs.

I've attached the Ullmann's text about phthalocyanines and a similar text from Kirk-Othmer together with the above mentioned Tetrahedron article to this post.


[Edited on 10-11-2005 by Mephisto]

Attachment: dossier.rar (786kB)
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unionised - 12-11-2005 at 12:36

Phthalate esters are widely used as plasticisers for PVC. You can extract the plasticiser from vinyl gloves by steeping them in alcohol, then hydrolyse the ester with aqueous NaOH. Acidify and you have phthalic acid.