DIMERIZATION CONSTANTS OF WATER-SOLUBLE PORPHYRINS IN AQUEOUS ALKALI

Spectrophotometric analysis of changes in absorption spectra on dilution of different 2,4-disubstituted derivatives of deuteroporphyrin yielded dimerization constants (KD) for each porphyrin in aqueous alkali. The KD values appear to be related to the hydrophobic/hydrophilic interactions of the system such that KD for proto- > meso- > deutero- > hemato- > coproporphyrin. The effects of alcohol, temperature, and ionic strength on the KD were examined. A simple approach to the graphic analysis of the dilution curves is presented for use when absorbance readings at A100 and A0 cannot be reliably determined, and the use of soluble porphyrins as model systems for studying hydrophobic/hydrophilic interactions in aqueous media is discussed. © 1979.