On the possibility of the direct preparation of the sodium salt of copper phthalocyanine-4-sulfonic acid

Abstract

The reaction of a 1:3 molar mixture of the monosodium salt of 4-sulfophthalic acid and phthalic acod, carried out in the presence of NH4Cl, urea, CuSO4 5H2O, and (NH4)2MoO4, does not yield the mono-substituted derivative, i.e., the sodium salt of copper-phthalocyanine-4-sulfonic acid (mSCuPc) but a 1:3 mixture of tetrasodium salt of copper-phthalocyanine-4-sulfonic acid-4,4',4'',4'''-tetrasulfonic acid (tSCuPc) and copper phthalocyanine (CuPc). However, quantum-mechanical calculations indicate that mSCuPc should be energetically favoured over the equivalent mixture of tSCuPc and CuPc. The preferential formation of the latter mixture has been attributed to kinetic factors arising from simultaneous presence of ionic and covalent species in the reaction medium.