Modifying the porphyrin core — a chemist's jigsaw

Core modified porphyrinoids are porphyrin analogs which differ from these by containing at least one non-pyrrolic aromatic ring. The result of core modification is to produce systems with novel and unique physical and electronic properties. In this review, the various possible core modified porphyrins and their syntheses are summarized starting by porphyrinoids with one pyrrolic nitrogen replaced followed by porphyrin-related macrocycles with two or more pyrrole rings exchanged. In addition the spectroscopic properties, especially the UV-vis absorption profiles and proton NMR shifts emanating from their core modifications are discussed and summarized in a table.