Synthesis of Di‐peri‐dinaphthoporphyrins by PtCl₂‐Mediated Cyclization of Quinodimethane‐type Porphyrins

Abstract

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 24π 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.

Porphyrinoids as a platform of stable radicals

“…Osuka et al also reported the similar peri -dinaphthoporphyrin 94 , 77 which comprises a partial structure of 91 and porphyrin tapes. 78 94 was characterized as a closed-shell anti-aromatic molecule ( Fig.…”

Synthesis and antiaromatic character of alkyl-substituted di-peri-dinaphthoporphyrin Ni(II) complex

“…The two stacked molecules are horizontally slipped with an offset distance of 2.664 Å [11b]. A similar dimeric stacking was also seen in the solid-state of 4Ni, and the interplane distance and the slip-stack offset distances were 3.455 and 2.813 Å, respectively [7]. Though the crystal packing force should be considered, the shorter packing distance in 5Ni implies a more facile p-stacking nature between two antiaromatic molecules due to less steric bulkiness of the peripheral alkyl groups.…”

“…5Ni displayed split first oxidation waves at 0.17 and 0.38 V and an additional wave at 0.82 V. 5Ni also showed two reversible reduction waves at -1.08 and -1.71 V. These peaks are negatively shifted as compared with those of 4Ni, and the relatively larger negative shifts in the reduction waves of 5Ni are consistent with the MO energy calculations. Notably, 4Ni also showed split oxidation waves at 0.31 and 0.38 V, and these two peaks likely correspond to each 0.5 electron oxidation process as compared with other peaks [7]. The differences between the first and second oxidation potentials (DE ox ) are 0.07 V for 4Ni and 0.21 V for 5Ni.…”

“…According to our previously reported protocol, 5Ni was synthesized in four steps from 5,15-diarylporphyrinato nickel(II) (Scheme 1) [7]. Oxidation of 5,15-diarylporphyrin by PbO 2 and following Corey-Fuchs reaction with tetrabromomethane in the presense of triphenylphosphine afforded tetrabromide 6Ni [8].…”

“…Several antiaromatic expanded porphyrins have been reported in the last decade, such as 28p hexaphyrin metal complex 3 [6], but they also bear sterically hindered meso-aryl-substituents. Recently, we have developed a new antiaromatic porphyrinoid, namely peri-naphthoporphyrin, 4M, which displayed a distinct antiaromatic character stemming from its 24p electronic circuit [7]. 4M possess two meso-aryl substituents at the 5,15-positions and four peripherally-substituted phenyl groups (defined as 23,24,28,29-positions, Fig.…”