Synthesis and Characterization of Water-Soluble / Phospholipid Bilayer Active, Polymer-Linked Porphyrins

The synthesis of porphyrins covalently linked to polyethylenimine (PEI) was accomplished by reacting an activated 5-(4-carboxyphenyl)-10,15,20-tri-p-tolylporphyrin either directly with PEI or after first attaching an w-amino acid of selected length. To introduce a linking chain between PEI and the porphyrin moiety, aminoaliphatic acid methyl esters were reacted with the acid chloride of the above porphyrin and the products were purified by column chromatography on silica gel followed by preparative thin-layer chromatography. Base-catalyzed hydrolysis of the methyl ester derivative gave the free acid. The carboxy functionality was then converted to the acid chloride by reaction with thionyl chloride followed by reaction with PEI in chloroform to give a nearly quantitative yield of the PEI-linked porphyrin. The polymer-linked porphyrins were purified by gel exclusion chromatography. Characterization and verification of structures were done by using NMR, UV/vis absorbance, and fluorescence emission spectroscopy. The resulting complexes are of considerable interest in model studies as the porphyrin portion readily inserts into lipid bilayer systems.