Synthesis and Characterization of <i>meso</i>-Aryl-Substituted Subchlorins

meso-Aryl-substituted subchlorins were obtained as a side product in acid-catalyzed subporphyrin synthesis and were fully characterized. Subchlorins were more efficiently prepared by reduction of subporphyrins with p-tosylhydrazide under basic conditions. Structural change from subporphyrin to subchlorin is accompanied by large optical and electrochemical changes that are quite similar to those observed upon change from porphyrin to chlorin. Optical and electrochemical properties of subchlorins are well understood within the framework of Gouterman's four-orbital theory.