π-Extended isomeric and expanded porphyrins.

The phenomenon of π-extension has been widely applied to, and exploited within, the field porphyrin chemistry. The development of reliable synthetic routes to various useful starting materials has facilitated the underlying preparative work. The chemical resemblance between porphyrins and expanded and isomeric porphyrins, as well as the increasing accessibility of the requisite starting materials is giving birth to the hybrid field of π-extended expanded and isomeric porphyrins. This tutorial review is intended to provide an overview of up-to-date published synthetic efforts and to summarize the effect of annulation on the properties of expanded and isomeric porphyrins.