Annulated Isomeric, Expanded, and Contracted Porphyrins.

Compared to porphyrin, its isomeric, expanded, and contracted analogues are less well explored. This contrast is found to be even more drastic in the case of their peripherally annulated counterparts. Nevertheless, the chemistry of annulated isomeric, expanded, and contracted porphyrins started flourishing recently with considerable efforts over the past few years, as evidenced by an increasing number of publications. While keeping the essence of porphyrins, these annulated versions exhibit quite unique properties that have no precedence in their nonannulated counterparts. An in-depth update of research carried out so far in this emerging area will be presented in this review.