Common Origin, Common Fate: Regular Porphyrin and N-Confused Porphyrin Yield an Identical Tetrapyrrolic Degradation Product

Abstract

The formation of an identical linear tetrapyrrole observed in the course of photooxidation of meso-tetraarylporphyrin and its N-confused isomer can be explained as a result of 1,2- and 1,3-dioxygen addition, respectively, as substantiated by DFT calculations.

Oxygenation of Phenanthriporphyrin and Copper(III) Phenanthriporphyrin: An Efficient Route to Phenanthribilinones

“…The second path deals with the formation of 4-Cu , hypothetically, yet which is not formed in the explored reaction conditions. The considered mechanism has also been based on previous investigations addressing the origin of carbonyl oxygen atoms in the cleavage product of regular porphyrins or metalloporphyrins. ,, For each explored route, four structures were optimized (namely, 1-Cu c -1 , 1-Cu c -2 , 3-Cu and 1-Cu t -1 , 1-Cu t -2 , 4-Cu ) as well as starting 1-Cu and a dioxygen molecule.…”

“…44 A mechanism, involving the cleavage of a C(11) meso −C(12) α bond adjacent to pyrrole by a dioxygen molecule, can be suggested by analogy to the previously observed reactivity of meso-aryl-substituted porphyrinoids or their complexes. 16,47 Oxygenation introduces a benzoyl group at the C( 11) phenanthrene (1-Cu) or phenantrenedione (2-Cu) adjacent positions and an oxygen atom at the terminal α-pyrrolic sites, affording 3-Cu and 5-Cu, respectively. The color changes from yellow to blue (1-Cu → 3-Cu) and from dark olive green to aquamarine (2-Cu → 5-Cu) in the course of the oxygenation reactions.…”

Creation from Confusion and Fusion in the Porphyrin World─The Last Three Decades of N-Confused Porphyrinoid Chemistry

“…The degradation of the porphyrin skeleton by photooxidation was well studied from the viewpoint of biological applications, such as photodynamic therapy . The final product of the photooxidation process of TPP dianion 82 or the corresponding metal complexes was determined to be the linear tetrapyrrolic compound 84 through the 1,2-cycloaddition of dioxygen to the C meso –C α bond (via 83 ). − In the case of the NCP skeleton, photodegradation proceeded through 1,3-cycloaddition (via 86 ) or 1,2-cycloaddition (via 87 ) to give the tetrapyrrolic compound, 84 or 88 , respectively. , …”

Iridium Complex of N‐Fused Bilatrienone: Oxidative Cleavage of N‐Fused Porphyrin Induced by Iridium‐Cyclooctadiene Complexation

“…Moreover, porphyrin analogs have demonstrated interesting reactivity toward oxidative degradation. For example, N‐confused porphyrin ( 6 ) [13–15] underwent oxidative ring cleavage to yield an N‐confused bilatrienone derivative ( 7 ) in an air‐saturated solution under photoirradiation (Figure 1b) [16] . Similarly, photooxidation of dithiaethyneporphyrin gave a ring‐opened product possessing a cumulene moiety [17] .…”