Corrins and porphyrins: two of nature’s pigments of life

Abstract

Given the relative scarcity of cobalt in the earth’s crust, its retention in biological systems, principally (but not exclusively) in the cobalt corrinoids or derivatives of vitamin B12, may be surprising. The chemistry of these compounds and the much more widely utilized iron porphyrins, is compared and contrasted and an attempt made to explain the retention of cobalt chemistry in biology.