5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1): A Stable Hückel Antiaromatic Hexaphyrin Stabilized by Intramolecular Hydrogen Bonding and Protonation-Induced Conformational Twist to Gain Möbius Aromaticity

Koji Naoda, Hirotaka Mori, Juwon Oh, Kyu Hyung Park, Dongho Kim, Atsuhiro Osuka

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1) 7 was prepared and characterized as a stable Hückel antiaromatic molecule with a dumbbell-like structure stabilized by effective intramolecular hydrogen bonding interactions involving the 2-pyridyl nitrogen atoms. Pd(II) metalation of 7 afforded two bis-Pd(II) complexes, 9-syn and 9-anti, whose structures are rigidly held by Pd(II) coordination, rendering 9-syn to be nonaromatic because of its highly distorted structure and 9-anti to be Hückel antiaromatic because of its enforced planar dumbbell structure. In contrast, protonation of 7 with methanesulfonic acid (MSA) led to the formation of its triprotonated species 7H3, which has been shown to take on twisted conformations with Möbius aromaticity in CH2Cl2, while the structure was held to be a planar rectangular conformation in the crystal. Excited-state dynamics were measured for 7, 7H3, 9-syn, and 9-anti, which indicated their electronic nature to be antiaromatic, aromatic, nonaromatic, and antiaromatic, respectively.

Original languageEnglish
Pages (from-to)11726-11733
Number of pages8
JournalJournal of Organic Chemistry
Volume80
Issue number23
DOIs
Publication statusPublished - 2015 Jul 28

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Protonation
Conformations
Hydrogen bonds
Excited states
Nitrogen
Atoms
Crystals
Molecules
methanesulfonic acid

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

Cite this

@article{82e06f09432f4079807faa0ecdfaca43,
title = "5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1): A Stable H{\"u}ckel Antiaromatic Hexaphyrin Stabilized by Intramolecular Hydrogen Bonding and Protonation-Induced Conformational Twist to Gain M{\"o}bius Aromaticity",
abstract = "5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1) 7 was prepared and characterized as a stable H{\"u}ckel antiaromatic molecule with a dumbbell-like structure stabilized by effective intramolecular hydrogen bonding interactions involving the 2-pyridyl nitrogen atoms. Pd(II) metalation of 7 afforded two bis-Pd(II) complexes, 9-syn and 9-anti, whose structures are rigidly held by Pd(II) coordination, rendering 9-syn to be nonaromatic because of its highly distorted structure and 9-anti to be H{\"u}ckel antiaromatic because of its enforced planar dumbbell structure. In contrast, protonation of 7 with methanesulfonic acid (MSA) led to the formation of its triprotonated species 7H3, which has been shown to take on twisted conformations with M{\"o}bius aromaticity in CH2Cl2, while the structure was held to be a planar rectangular conformation in the crystal. Excited-state dynamics were measured for 7, 7H3, 9-syn, and 9-anti, which indicated their electronic nature to be antiaromatic, aromatic, nonaromatic, and antiaromatic, respectively.",
author = "Koji Naoda and Hirotaka Mori and Juwon Oh and Park, {Kyu Hyung} and Dongho Kim and Atsuhiro Osuka",
year = "2015",
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language = "English",
volume = "80",
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5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1) : A Stable Hückel Antiaromatic Hexaphyrin Stabilized by Intramolecular Hydrogen Bonding and Protonation-Induced Conformational Twist to Gain Möbius Aromaticity. / Naoda, Koji; Mori, Hirotaka; Oh, Juwon; Park, Kyu Hyung; Kim, Dongho; Osuka, Atsuhiro.

In: Journal of Organic Chemistry, Vol. 80, No. 23, 28.07.2015, p. 11726-11733.

Research output: Contribution to journalArticle

TY - JOUR

T1 - 5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1)

T2 - A Stable Hückel Antiaromatic Hexaphyrin Stabilized by Intramolecular Hydrogen Bonding and Protonation-Induced Conformational Twist to Gain Möbius Aromaticity

AU - Naoda, Koji

AU - Mori, Hirotaka

AU - Oh, Juwon

AU - Park, Kyu Hyung

AU - Kim, Dongho

AU - Osuka, Atsuhiro

PY - 2015/7/28

Y1 - 2015/7/28

N2 - 5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1) 7 was prepared and characterized as a stable Hückel antiaromatic molecule with a dumbbell-like structure stabilized by effective intramolecular hydrogen bonding interactions involving the 2-pyridyl nitrogen atoms. Pd(II) metalation of 7 afforded two bis-Pd(II) complexes, 9-syn and 9-anti, whose structures are rigidly held by Pd(II) coordination, rendering 9-syn to be nonaromatic because of its highly distorted structure and 9-anti to be Hückel antiaromatic because of its enforced planar dumbbell structure. In contrast, protonation of 7 with methanesulfonic acid (MSA) led to the formation of its triprotonated species 7H3, which has been shown to take on twisted conformations with Möbius aromaticity in CH2Cl2, while the structure was held to be a planar rectangular conformation in the crystal. Excited-state dynamics were measured for 7, 7H3, 9-syn, and 9-anti, which indicated their electronic nature to be antiaromatic, aromatic, nonaromatic, and antiaromatic, respectively.

AB - 5,20-Di(pyridin-2-yl)-[28]hexaphyrin(1.1.1.1.1.1) 7 was prepared and characterized as a stable Hückel antiaromatic molecule with a dumbbell-like structure stabilized by effective intramolecular hydrogen bonding interactions involving the 2-pyridyl nitrogen atoms. Pd(II) metalation of 7 afforded two bis-Pd(II) complexes, 9-syn and 9-anti, whose structures are rigidly held by Pd(II) coordination, rendering 9-syn to be nonaromatic because of its highly distorted structure and 9-anti to be Hückel antiaromatic because of its enforced planar dumbbell structure. In contrast, protonation of 7 with methanesulfonic acid (MSA) led to the formation of its triprotonated species 7H3, which has been shown to take on twisted conformations with Möbius aromaticity in CH2Cl2, while the structure was held to be a planar rectangular conformation in the crystal. Excited-state dynamics were measured for 7, 7H3, 9-syn, and 9-anti, which indicated their electronic nature to be antiaromatic, aromatic, nonaromatic, and antiaromatic, respectively.

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