Novel porphyrinoids

Abstract

The Porphyrins and their metal complexes, referred to as the pigments of life (Battersby), have developed into a major interdisciplinary area of research encompassing chemistry, physics (specifically photophysics), and medicine. Surprisingly, despite the plethora of work on these tetrapyrrolic macrocycles, quite a number of formally very simple porphyrin structural variants have hitherto eluded scientific attention and scrutiny. On looking at the prophyrins from the “annulene chemist' ‘s’’ point of view, i.e., by focusing on the interplay between molecular design and π-electron structure, one gets captivated by molecules such as porphycene and porphyrins in which the nitrogen atoms have been replaced by carbon, oxygen, chalcogen, or even phosphorus atoms. As reported three years ago, porphycenes can be prepared relatively easily and are found to resemble the porphyrins in many respects. Although porphycenes possess a coordination hole that is smaller than that of porphyrins, they are capable of complexation with many metal ions to give the respective metalloporphycenes. Very recently, the furan, thiophene, and the selenophene analogues of porphyrin, which exist as dications, have also yielded to synthesis (the selenium compound so far obtained only in solution). While these ionic species are reminiscent of pyrylium ions chemically, they clearly qualify as porphyrinoid in terms of spectral properties and molecular structure. © 1990, IUPAC.