The first synthetic porphyrin isomer was reported by Emanual Vogel and coworkers in 1986.  This isomer [18]porphyrin-(2.0.2.0) is named as porphycene, and the central N Cavity forms a rectangle shape as shown in figure. Porphycenes showed interesting photophysical behavior and found versatile compound towards the photodynamic therapy. This inspired Vogel and Sessler to took up the challenge of preparing [18]porphyrin-(2.1.0.1) and named it as corrphycene or porphycerin. The third porphyrin that is [18]porphyrin-(2.1.1.0), was reported by Callot and Vogel-Sessler. Vogel and coworkers reported successful isolation of [18]porphyrin-(3.0.1.0) or isoporphycene. The Japanese scientist Furuta and Polish scientist Latos-Grażyński almost simultaneously reported the N-confused porphyrins. The inversion of one of the pyrrolic subunits in the macrocyclic ring resulted in one of the nitrogen atoms facing outwards from the core of the macrocycle.