Synthesis of Hangman Chlorins.

Two complementary rational synthetic routes have been developed in order to synthesize hangman chlorins, which differ with regard to the order of the installation (pre- and post-formation of the chlorin macrocycle) and position of the xanthene backbone about the chlorin periphery. The versatility of the synthetic method is demonstrated with the preparation of ten new hangman chlorins bearing a xanthene backbone and a pendant carboxylic acid. Cyclic voltammograms of hangman chlorins exhibit a hangman effect derived from intermolecular proton transfer. This hangman effect is manifested in catalytic hydrogen evolution production.