I have some doubts regarding the synthesis of naphthalocyanines. I have seen several methods for preparing Naphthalocyanines like the following:
i) treating the naphthalonitrile with a base like DBU and metal in high boiling solvents like n-butanol.
ii) naphthalonitrile with metal, ammonium molybdate in quinoline at around 2000C.
iii) naphthalonitrile with metal, ammonium sulfate, HMDS in DMF at 1000C.
iv) naphthalonitrile with LiOMe, metal salt in i-AmOH in reflux.
v) And in last, naphthalonitrile is treated with Li metal in high boiling alcohols for generating naphthalocyanines without metal at the center.
I am really confused about all these methods. Which method is better for obtaining Metal-Naphthalocyanines? Any suggestions will be a great help to me. And I am not sure how to extract out the Napthalocyanines from the reaction mixture after completion of reaction as for that also there are several methods, so suggestions in that area are also appreciated.
Hi, there is no standard and general method which works for all kinds of naphthalonitrile derivatives. substituents greatly influence the cyclization and reactivity of starting material. generally people start with first method you mentioned. if it fails, then go to next methods. HMDS is newer reagent for the activation of CN group and I have used this reagent for Pc synthesis at mild conditions. there is no need of amm. sulfate in this method.
isolation of compounds is usually done by diluting the reaction mixture with methanol or water. mostly Ncs are insoluble in water or alcohol.
hope for the best!
Thank you very much @ Zafar Iqbal for your kind reply. Regarding the purification methods I still have some doubts. I tried the method you suggested, like precipitating in water:methanol mixture. I got rid of many impurities by that method, but still there are impurities which is not going by washing the naphthalocyanines with methanol. So I read a lot of literature article and found that mostly these molecules are purified by size exclusion chromatography. Especially by using Bio Beads SX-1. I tried that too but I am not able to see any seperation in that column. I did the size exclusion using THF as solvent as my compound is soluble in THF. Do you know any sort of standard procedure for doing size exclusion chromatography using bio beads or could you please suggest any other alternatives? Also for your kind attention, I did tried silica and alumina but my compound has some amino moieties present in the periphery and hence these doesnt move in sililca or alumina. (If I use trifluoroacetic acid or triethylamine the compound does move but the impurities will be also moving.)
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