Endocyclic Extension of Porphyrin π‐System by Interior Functionalization of N‐Confused Porphyrins

Abstract

Internally alkynylated or cyanated N-confused porphyrins have been prepared, and these have been characterized by NMR, UV/Vis/NIR absorption, and X-ray analysis. The desired porphyrins have been synthesized by interconversion between an N-confused porphyrin and an N-fused porphyrin. In the case of terminal alkyne derivatives, intramolecular addition of a pyrrolic NH moiety to the triple bond occurred at ambient temperature to give etheno-bridged N-confused porphyrins. Significant bathochromic shifts in the absorbances of these compounds may be reasonably explained in terms of an increase in their HOMO energy levels due to effective overlap of the porphyrin pi-orbital and the bridged alkene pi-orbital. The corresponding rhodium(I) complexes have also been prepared, and these have been characterized by NMR and X-ray analysis.

Singly N‐Confused [26]Hexaphyrin: A Binucleating Porphyrinoid Ligand for Mixed Metals in Different Oxidation States

“…[17] This result would constitute the first explicit example of metal-assisted endocyclic extension of porphyrin p-system. [17] This result would constitute the first explicit example of metal-assisted endocyclic extension of porphyrin p-system.…”

“…Such participation of the p-orbital inside the aromatic annulenic substructure causes an unusually narrow HOMO-LUMO energy gap as observed in a series of ring-fused porphyrinoids. [17] This result would constitute the first explicit example of metal-assisted endocyclic extension of porphyrin p-system. From the viewpoint of metal electronic states, metal-metal interaction through the C = C p-orbital could be expected, although no clear experimental evidence has been obtained so far.…”

Blooming of confused porphyrinoids—fusion, expansion, contraction, and more confusion

“…29b). 140,141 A significant increase of the HOMO energy level is observed in the etheno-bridged NCP, resulting a large red-shift in the absorption spectrum. In addition, azoxy-(Fig.…”

Nucleophilic Aromatic Substitution (SNAr) and Related Reactions of Porphyrinoids: Mechanistic and Regiochemical Aspects

“…Since their inception, much attention has been paid to modifying the core of this macrocycle. [ 179 ] In the present context it is necessary to focus on the S N Ar at the C 3 ‐ and C 21 ‐positions. The differing reactivates of these two positions is evident; noted from early on was the carbene character of the C 21 ‐position, [ 180 ] and hence along with this come intriguing coordination properties, [ 181 ] particularly of larger metals in unusual oxidation states.…”