Enhancement of solubility via esterification: Synthesis and characterization of octakis (ester)-substituted phthalocyanines

Metal-free and metallophthalocyanines (M = Zn, Ni and ClFe) carrying eight hydroxyethylsulfanyl groups at peripheral positions were prepared from 4,5-bis(hydroxyethylsulfanyl)phthalonitrile. The reactivity of the hydroxyethyl groups was demonstrated by esterification of phthalocyanine derivatives with pyridine-4-carboxylic acid and also ferrocenecarboxylic acid in the presence of dicyclohexylcarbodiimide combined with N,N-dimethylaminopyridine or p-toluenesulfonic acid and acetic anhydride. Unlike the parent phthalocyanines, the symmetrically functionalized phthalocyanines with eight ester units were soluble in common organic solvents such as CHCl3, THF, pyridine and DMF, sparingly soluble in ethanol and acetone and insoluble in water and hexane. The newly synthesized compounds were characterized by elemental analysis, IR, UV–vis, FAB-MS and 1H NMR spectroscopy.