ABSTRACT
A conspicuous group of natural macrocyclic pigments among the great diversity of macroheterocyclic compounds are hemoglobins, chlorophylls, cytochromes and other species. They play an exceptional role in vital processes of photosynthesis and respiration, are involved in regulation of fine metabolic processes in living organisms. These substances are tetrapyrrole macroheterocyclic compounds (porphyrins), the basis of which is porphin 1. It
has a planar structure, and their inner macroring consisting of 16 carbon and nitrogen atoms contains 18 π-electrons and is aromatic.
