THE EFFECTS OF PERIPHERAL SUBSTITUENTS ON THE KINETICS OF ZINC ION INCORPORATION AND ACID-CATALYZED REMOVAL FROM WATER-SOLUBLE SULFONATED PORPHYRINS

The kinetics of Zn2+ and Zn(OH)(+) incorporation into and the kinetics of the acid catalyzed removal of Zn(II) from twelve water-soluble, sulfonated derivatives of tetraphenylporphyrin with alkyl or halogen groups in the para, ortho or di-ortho positions were investigated. While the incorporation reactions showed little dependence on porphyrin basicity, the Zn-P (P = porphyrin derivative) acid solvolysis reactions were faster the higher the basicity of the free base (H-2-P) compound. Equilibrium constants for the formation of cadmium porphyrins decreased with an increase in porphyrin basicity. The predeformed tetrakis(4-sulfonatophenyl)-beta-octatbromo reacted with Zn2+ about 10(3) times faster than porphyrins of similar basicity. These results indicate how substituents on the phenyl and beta-pyrrole rings influence the solution chemistry of water soluble porphyrins.