meso‐Aryl [20]π Homoporphyrin: The Simplest Expanded Porphyrin with the Smallest Möbius Topology

Abstract

An unstable conjugated homoporphyrin was successfully stabilized by introducing meso-aryl substitutents. It was evident from the moderate diatropic ring current found by NMR analysis that the newly formed 20π conjugated free base and its protonated form exhibited Möbius aromatic character. Furthermore, complexation as a ligand with an Rh ion afforded a unique binding mode and retained the Möbius aromaticity. Overall, these compounds are the smallest Möbius aromatic molecules, as confirmed by spectral and crystal-structure analysis and supported by theoretical studies.

Homocarbaporphyrinoids: The m‐o‐m and p‐o‐p Terphenyl Embedded Expanded Porphyrin Analogues and Their RhI Complexes

“…Recently, Ravikanth and co‐workers reported a stable non‐aromatic 20π‐core‐modified homoporphyrins, such as [20]dithiahomoporphyrin(2.1.1.1) and [20]dioxahomoporphyrin (2.1.1.1) ( I ), by incorporating dithia‐ and dioxaethene into the macrocylic core . Very recently, we have demonstrated the synthesis of aza‐homoporphyrin II , which exhibits the smallest Möbius topology in three different forms, that is, neutral, protonated, and Rh I complex . However, the respective carba‐analogue of the homoporphyrin is hitherto unknown in the literature, although carbaporphyrinoids have attracted significant attention due to their unique macrocyclic environment .…”

Covalently Linked meso‐BODIPYnyl Dithiahomoporphyrins: Synthesis and Properties

“…The frequencies for 13 4 ] was used as an internal standard for 1 H and 13 C NMR, tetrafluorotoluene and boric acid as external standards for 19 F NMR and 11 B NMR, respectively. All other chemicals used for the synthesis were reagent grade unless otherwise specified.…”

“…[8][9][10][11][12] As shown in Scheme 1a, the appropriate formyl-BODIPY such as meso-(4formyl phenyl) BODIPY (8), -formyl meso-anisyl BODIPY (9), meso-(2-formyl pyrrolyl) BODIPY (10) and α-(2-formyl-pyrrolyl) BODIPY (11) was treated with equimolar tetrapyrrane 7 in CH 2 Cl 2 in the presence of catalytic amount of BF 3 .OEt 2 at room temperature under inert atmosphere for 15-20 min followed by oxidation with 2 equiv. We made an attempt to synthesize the meso-aza BODIPYnyl homoporphyrin 5 by following the similar procedure used for the synthesis of compounds (1)(2)(3)(4). The progress of the reaction was followed by TLC analysis and absorption spectroscopy.…”

“…[5,6] We also showed that the [20 π]dithiaporphyrin (2.1.1.1) (II) can be used as an exclusive sensor for Hg II ion. [4] They also showed that [20π]homoporphyrins complexes readily with Rh I ion (IV-Rh) and demonstrated that these [20π]homoporphyrins are smallest Möbius aromatic macrocycles. [4] They also showed that [20π]homoporphyrins complexes readily with Rh I ion (IV-Rh) and demonstrated that these [20π]homoporphyrins are smallest Möbius aromatic macrocycles.…”

“…[1][2][3] The homoporphyrin macrocycles are simplest higher homologues of [18π]porphyrin (1.1.1.1) and unlike porphyrins, the homoporphyrins are non-aromatic. [3,4] Recently, we reported the synthesis of first stable non-aromatic core-modified homoporphyrins called [20 π]dithiaporphyrin (2.1.1.1) (II) and [20π]dioxaporphyrin (2.1.1.1) (III) by condensing readily available dithienylethene diol and difuranylethene diol, respectively with meso-aryl dipyrromethane under acid catalyzed macrocyclization reaction conditions. [3,4] Recently, we reported the synthesis of first stable non-aromatic core-modified homoporphyrins called [20 π]dithiaporphyrin (2.1.1.1) (II) and [20π]dioxaporphyrin (2.1.1.1) (III) by condensing readily available dithienylethene diol and difuranylethene diol, respectively with meso-aryl dipyrromethane under acid catalyzed macrocyclization reaction conditions.…”