Synthesis of di-peri-dinaphthoporphyrins by PtCl₂-mediated cyclization of quinodimethane-type porphyrins

Di-peri-dinaphthoporphyrins can be regarded as a key and common substructure of fused porphyrinoids. PtCl₂-mediated cycloisomerization reaction of quinodimethane-type porphyrins provided these doubly fused porphyrins, which exhibit characteristic paratropic ring currents that presumably arise from 24 π antiaromatic circuit as a dominant resonance contributor. UV/Vis absorption spectra, cyclic voltammetry, and excited-state dynamics as well as theoretical calculation support this conclusion. The core of the matter: Di-peri-dinaphthoporphyrins have been synthesized by PtCl₂-mediated cycloisomerization reaction of quinodimethane-type porphyrins. These porphyrins can be regarded as a key substructure of fused porphyrinoids, for which a 24π antiaromatic circuit was proven to be a dominant resonance contributor by ¹H NMR, UV/Vis absorption, cyclic voltammetry, NICS calculations, and AICD plot.