A less preferred term for dipyrrins. (The term 'pyrromethane' has been used for the system with a
–CH2– linkage).
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1361 (https://doi.org/10.1351/pac199567081307)