Effect of pH on acid-base and photophysicochemical properties of 2,3,9,10,16,17,23,24-octacarboxyphthalocyanines in aqueous media

Abstract

The results of study of pH effect on the aggregation, acid-base and photophysicochemical properties of 2,3,9,10,16,17,23,24-octacarboxy substituted Zn, Al, Co, Pt and Pd phthalocyanines (MPcoc) in aqueous media are presented. The ionization of peripheral carboxyl groups and axial ligation of central metal atom are the principal factors, governing aggregation. The multi-step ionization of MPcocs, induced by change of pH, was considered as pseudo two-step process affecting four carboxyl groups on each step. The photophysicochemical properties of three differently ionized forms of ZnPcoc (unionized, tetra- and octacarboxylated) were studied.