Disruption of Antiaromaticity in Structurally Related Expanded Porphyrin-like Macrocycles with Benzene Linkers

Abstract

Phenylene-linked cyclotrimer (3T) and cyclotetramer (4T) have been synthesized via Lewis acid-catalyzed selfcondensation of appropriate precursors. Structural and Density Functional Theory (DFT) studies reveal the disruption of annulenic conjugation in both 3T and 4T by linking phenylene rings prevented them from global antiaromaticity. The single crystal X-ray structure of 4T reveals all the nitrogens are pointing toward the macrocyclic core with near-planar and square-shaped geometry, thus in sharp contrast to the ring-strained conformation of 3T.

Recent Research Progress and Perspectives on Porphyrin-Based Porous Photocatalysts in the Field of CO2 Reduction

“…Hydrogen on pyrrole nitrogen of the porphyrin core can be replaced by metal ions to form metal porphyrins, while the hydrogen ions in peripheral methylene can be replaced by phenyl, pyridyl, phenylhydroxy, benzenesulfonic acid, and other groups to form porphyrin derivatives . Porphyrin belongs to the π–π conjugated macrocyclic system, around which the delocalization phenomenon of surrounding electrons is obvious, and its molecule has strong rigidity and aromatic properties . The above characteristics are beneficial to the transfer and separation of photogenerated electrons.…”

“…9 Porphyrin belongs to the π−π conjugated macrocyclic system, around which the delocalization phenomenon of surrounding electrons is obvious, and its molecule has strong rigidity and aromatic properties. 10 The above characteristics are beneficial to the transfer and separation of photogenerated electrons. The large planar π-conjugated structure of porphyrins has inherent properties, such as photon absorption, high thermal stability, efficient electron transfer, absorption in the ultraviolet−nearinfrared region, high fluorescence, and efficient lighting.…”

“…Topologically guided HOFs based on the self-assembly process of quaternary porphyrin synthons have a predictable square-layer topology (SQL), but their stability is unsatisfactory. A HOF with the predicted SQL, named PFC-72-Co, prepared by[5,10,15,20tetrakis(4-carboxyphenyl)porphyrin] (TCPP) or [5,10,15,20tetrakis(4-carboxyphenyl)porphrin]-Co through an organic reaction under 130 °C for 2 days showed a 14.7 μmol h −1 g −1 CO yield (Figure…”

Synthesis and Properties of Nonaromatic Meta‐Benziheptaphyrins and Aromatic Para‐Benziheptaphyrins

“…Lash's group [8,15,28] and Latos‐Grażyński's group [10,19,20,27,29–31] and others [20,21,23,32–35] have extensively investigated the phenylene containing porphyrinoids, discussed their aromatic characteristics and shown their ability to form organometallic complexes by involving phenylene “C” along with pyrrole “N”s in coordination. Although the aromatic nature of m / p ‐phenylene containing porphyrins have been studied to greater extent but the aromaticity was not investigated thoroughly with m / p ‐phenylene containing expanded porphyrinoids since the reports on m / p ‐phenylene containing expanded porphyrins are relatively very few [20,33,36–39] . We recently reported the synthesis of [24π] dithia meta ‐benzisapphyrins 1 and [22π] dithia para ‐benzisapphyrins 2 and showed that the dithia p ‐benzisapphyrins 2 were aromatic whereas the dithia m ‐benzisapphyrins 1 were nonaromatic in nature [33] .…”

“…Although the aromatic nature of m/p-phenylene containing porphyrins have been studied to greater extent but the aromaticity was not investigated thoroughly with m/pphenylene containing expanded porphyrinoids since the reports on m/p-phenylene containing expanded porphyrins are relatively very few. [20,33,[36][37][38][39] We recently reported the synthesis of [24π] dithia meta-benzisapphyrins 1 and [22π] dithia parabenzisapphyrins 2 and showed that the dithia p-benzisapphyrins 2 were aromatic whereas the dithia m-benzisapphyrins 1 were nonaromatic in nature. [33] In continuation of our efforts in synthesizing more examples of expanded m/p-benziporphyrinoids to understand their structure, spectral and aromatic properties, herein we report our successful synthesis of nonaromatic [32π] m-benziheptaphyrins 3 a/3 b and aromatic [30π] p-benziheptaphyrins 4 a/4 b by adopting [5 + 2] condensation strategy using readily synthesized precursors.…”