Radicals of isobacteriochlorins: models of siroheme and sirohydrochlorin

To probe the magnetic, optical, and redox characteristics of the isobacteriochlorin class, described here are molecular orbital calculations and ESR, ENDOR, optical, and electrochemical results for two model compounds: zinc tetraphenyl isobacteriochlorin, whose recently determined x-ray structure verifies that two adjacent pyrrole rings are reduced in isobacteriochlorins, and dimethyloctaethyl isobacteriochlorin, a compound which is a close analogue, structurally and spectrally to sirohydrochlorin. 5 figures, 1 table.