Extroverted Confusion—Linus Pauling, Melvin Calvin, and Porphyrin Isomers

Porphyrins may be confused, but Linus Pauling and Melvin Calvin were not! Calvin proposed “carboporphyrins” in 1943 and, unbeknownst to contemporary science, Pauling contemplated the existence and stability of such fundamental porphyrin isomers in 1944. What he called “isoporphyrins” with “extroverted pyrrole rings”, nowadays called N-confused porphyrins, were discovered 50 years later in 1994 by Furuta and Latos-Grażyński et al.