Interfacial adsorption and ion-association extraction of protonated tetraphenylporphyrin and octaethylporphyrin

Protonation of tetraphenylporphyrin (TPP) and octaethylporphyrin (OEP) in toluene/acid systems was investigated by a high-speed stirring method. In toluene/sulfuric acid system, the adsorption of the diprotonated TPP and the monoprotonated OEP at the liquid-liquid interface was found, while in other acid systems including hydrochloric acid, perchloric acid, and trichloroacetic acid, the ion-association extraction of H2TPP2+ and HOEP(+) was observed as well, depending on the nature of the counter anions and the concentration of the acids. An inverted correlation was suggested between the adsorption constants of the protonated porphyrins and the extraction constants of the acids with the porphyrins.