Aromaticity and tautomerism in porphyrins and porphyrinoids

Stępień, M.; Latos-Grażyński, L.
Top. Heterocycl. Chem. 2009, 19, 83–153 | view at publisher's site

Porphyrins and their analogues constitute one of the most important families of aromatic macrocycles. The present review discusses aromaticity of porphyrinoids, focusing mainly on non-expanded systems. The effect of structural modifications on the aromaticity-dependent properties of porphyrin-like macrocycles is described. It is shown that delocalization modes observed in porphyrinoids can be classified using a simple valence-bond approach. Aromaticity of porphyrinoids is further discussed as a function of tautomerism, coordination chemistry, and the oxidation state of the macrocycle.