MEASUREMENT OF ASSOCIATION CONSTANTS BETW EEN METAL-IONS AND PORPHYRIN OR METALLOPORPHYRINS BEFORE THEIR COMPLEXATION OR REPLACEMENT REACTION USING A HYDROPHOBIC RESIN COLUMN

The existence of intermediate species during complex formation between metal ions and porphyrin in aqueous solution was confirmed using an A mberlite XAD-2 resin column. When porphyrin solution is injected into the metal ion solution stream, the porphyrin adsorbed to the XAD colum n with the metal ions associated or complexed with it, and the decreas e of the metal ion in solution is observed in the column eluant. Calcu lated from the decrease, the association constants of Cu2+ and Zn2+ wi th alpha, beta, gamma, delta-tetrakis(4-N-methylpyridyl)porphine (TMPy P) are 32 (10 degrees C) and 57 M(-1) (25 degrees C), respectively. It was also confirmed that the intermediate exists before the metal repl acement reaction between Cu2+ and the metalloporphyrin complex. The as sociation constant in the Cu2+/Zn-TMPyP system was especially large. A s mentioned above, the interaction of the metal ion and the ligand bef ore complex formation can be investigated by separating the ligand wit h the attached metal ion from the free metal ion using the hydrophobic interaction between the column and the ligand. These results were in good agreement with the values obtained by the kinetic method.