The 31-hydroxy group of a chlorophyll-a derivative was substituted with an acetylthio moiety and the resulting thioester was methanolyzed in the presence of a base to give its chlorin dyad covalently linked with a disulfide bond without the isolation of the corresponding 31-sulfanyl-chlorin. The thiol-type chlorin monomer was obtained by the reductive cleavage of the disulfide dyad. Its zinc complex with the 31-sulfanyl group was also prepared from the reduction of the zinc chlorin dyad, but not from the zinc metalation of the free base monomer. The semi-synthetic zinc 31-sulfanyl-131-oxo-chlorin was primarily monomeric in an aqueous micelle as well as a non-polar organic solvent. In a diluted solution of the disulfide with free base and its zinc complex moieties, the excited energy transfer from the latter to former part occurred, but no further intramolecular energy transfer was observed under the reduction conditions breaking the disulfide bond.