State and kinetic stability of chloro derivatives of copper(II) phthalocyanine in concentrated sulfuric acid

The electronic absorption spectra in aprotic organic solvents and in variou s-concentration sulfuric acid and the kinetic stability of copper tetra(3-c hloro)- and tetra(4-chloro)phthalocyanines in concentrated sufuric acid wer e examined as a function of solvent composition and temperature. The kineti c equations and the parameters of the dissociation of the complexes by the donor-acceptor bonds were determined. The previously reported kinetic param eters for related nitro, nitrobromo, and carboxy derivatives were used to c onstruct a universal (with respect to solvent composition) stability order of functional derivatives of copper phthalocyanines. The places of the comp ounds in the stability order are discussed in terms of the electronic and s teric effects of the substituents on the electron density on the Cu-N bonds with account for the sigma,pi nature of these bonds and the nature of acti vation of the reacting system copper phthalocyanine-sulfuric acid.