A homologous series of water-soluble porphyrins and metalloporphyrins: Synthesis, dimerization, protonation and self-complexation
✍ Scribed by William I. White; Robert A. Plane
- Publisher
- Elsevier Science
- Year
- 1974
- Weight
- 904 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0006-3061
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✦ Synopsis
4 homologous series of watersoluble porphyrins was prepared by reacting diamiics of the type HIN(CHt),NH&z = 2,3,4, 6) with pmtoporphyrin IX dimethyl ester. There was addition of a diamine to each vinyl group and replacement of the alcohol moiety of each ester group by a diamine. The dimerization of the porphyrins in this series in aqueous solution was studied ss a functian of the length of the diamine chain, ionic strength, percent of added alcohol, and temperature. Values for log KD at 2S"C, determined by ultraviolet-visible spectroscopy, ranged from 4.8 for the porphyrin formed with n = 6 to 6.5 for the porphyrin formed with n = 2 in 0.1 iIi NaCl. Protonation behavior was studied; it was found that the monocation and the dication of the monomer and of the dimer have acid dissociation constants of approximately 10-J. Copper and zinc were inserted and the aggregation of these metallaporphyrins wss studied. When the pH was raised above 8 for the zinc porphyrins, spectral changes occurred which indicated that the side arms of the porphyrins were selfcomplexing with the metal in the middle for the porphyrins formed where IL = 3,4,6 but not for the porphyrin formed where n = 2. INTRODUcTIoN MetalIoporphyrins are of great biological significance, and as the biological environment is essentially aqueous, it is desirable to study these porphyrins in water. Proteins are the principle solublizing agents for porphyrins found in nature, but water-soluble porphyrins permit studies of metal-porphyrin systems, witbout the infiuence of the protein, which may