Porphyrins with Five-Membered Ring Substituents on meso-Position and their Derivatives

Abstract

Tetrapyrrolic porphyrins are the molecules of choice for nature where light absorption and metal based chemistry plays an important role in biological systems. Constant efforts are directed at modifying the porphyrin skeletal structure to result in porphyrins with fine-tuned physical properties. This review focusses on the chemistry of porphyrins with five-membered aromatic rings such as furan, pyrrole and thiophene as substituents at the meso position of porphyrins. Substitution with these five-membered rings at the meso-position of porphyrins brings about significant modulation of HOMO-LUMO gap, which reflects in shifts in the absorption and fluorescence spectra and in their electrochemical properties compared to the conventional porphyrins with six-membered aryl substituents. The synthetic modification of these five-membered rings by introdcution of various functional groups were also discussed.