Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)

Jeyaraman Sankar, Shigeki Mori, Shohei Saito, Harapriya Rath, Masaaki Suzuki, Yasuhide Inokuma, Hiroshi Shinokubo, Suk Kim Kil, Seok Yoon Zin, Jae Yoon Shin, Min Lim Jong, Yoichi Matsuzaki, Osamu Matsushita, Atsuya Muranaka, Nagao Kobayashi, Dongho Kim, Atsuhiro Osuka

Research output: Contribution to journalArticle

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Abstract

meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by 1H, 13C, and 19F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25°C exist largely as an equilibrium among several rapidly interconverting twisted Möbius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or Möbius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100°C in THF, these rapid interconversions among Möbius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a Möbius conformation. Detailed analyses of the solid-state Möbius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic π-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable Möbius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.

Original languageEnglish
Pages (from-to)13568-13579
Number of pages12
JournalJournal of the American Chemical Society
Volume130
Issue number41
DOIs
Publication statusPublished - 2008 Oct 15

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Conformations
Spectrum Analysis
Porphyrins
Circular Dichroism
Crystallization
X-Ray Diffraction
Magnetic Resonance Spectroscopy
Metals
Temperature
Circular dichroism spectroscopy
Ultraviolet spectroscopy
Absorption spectroscopy
X ray diffraction analysis
Nuclear magnetic resonance spectroscopy
Demonstrations
Single crystals
Carbon-13 Magnetic Resonance Spectroscopy

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Sankar, Jeyaraman ; Mori, Shigeki ; Saito, Shohei ; Rath, Harapriya ; Suzuki, Masaaki ; Inokuma, Yasuhide ; Shinokubo, Hiroshi ; Kil, Suk Kim ; Zin, Seok Yoon ; Shin, Jae Yoon ; Jong, Min Lim ; Matsuzaki, Yoichi ; Matsushita, Osamu ; Muranaka, Atsuya ; Kobayashi, Nagao ; Kim, Dongho ; Osuka, Atsuhiro. / Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1). In: Journal of the American Chemical Society. 2008 ; Vol. 130, No. 41. pp. 13568-13579.
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title = "Unambiguous identification of M{\"o}bius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)",
abstract = "meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by 1H, 13C, and 19F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25°C exist largely as an equilibrium among several rapidly interconverting twisted M{\"o}bius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or M{\"o}bius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100°C in THF, these rapid interconversions among M{\"o}bius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a M{\"o}bius conformation. Detailed analyses of the solid-state M{\"o}bius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic π-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable M{\"o}bius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.",
author = "Jeyaraman Sankar and Shigeki Mori and Shohei Saito and Harapriya Rath and Masaaki Suzuki and Yasuhide Inokuma and Hiroshi Shinokubo and Kil, {Suk Kim} and Zin, {Seok Yoon} and Shin, {Jae Yoon} and Jong, {Min Lim} and Yoichi Matsuzaki and Osamu Matsushita and Atsuya Muranaka and Nagao Kobayashi and Dongho Kim and Atsuhiro Osuka",
year = "2008",
month = "10",
day = "15",
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pages = "13568--13579",
journal = "Journal of the American Chemical Society",
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Sankar, J, Mori, S, Saito, S, Rath, H, Suzuki, M, Inokuma, Y, Shinokubo, H, Kil, SK, Zin, SY, Shin, JY, Jong, ML, Matsuzaki, Y, Matsushita, O, Muranaka, A, Kobayashi, N, Kim, D & Osuka, A 2008, 'Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)', Journal of the American Chemical Society, vol. 130, no. 41, pp. 13568-13579. https://doi.org/10.1021/ja801983d

Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1). / Sankar, Jeyaraman; Mori, Shigeki; Saito, Shohei; Rath, Harapriya; Suzuki, Masaaki; Inokuma, Yasuhide; Shinokubo, Hiroshi; Kil, Suk Kim; Zin, Seok Yoon; Shin, Jae Yoon; Jong, Min Lim; Matsuzaki, Yoichi; Matsushita, Osamu; Muranaka, Atsuya; Kobayashi, Nagao; Kim, Dongho; Osuka, Atsuhiro.

In: Journal of the American Chemical Society, Vol. 130, No. 41, 15.10.2008, p. 13568-13579.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)

AU - Sankar, Jeyaraman

AU - Mori, Shigeki

AU - Saito, Shohei

AU - Rath, Harapriya

AU - Suzuki, Masaaki

AU - Inokuma, Yasuhide

AU - Shinokubo, Hiroshi

AU - Kil, Suk Kim

AU - Zin, Seok Yoon

AU - Shin, Jae Yoon

AU - Jong, Min Lim

AU - Matsuzaki, Yoichi

AU - Matsushita, Osamu

AU - Muranaka, Atsuya

AU - Kobayashi, Nagao

AU - Kim, Dongho

AU - Osuka, Atsuhiro

PY - 2008/10/15

Y1 - 2008/10/15

N2 - meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by 1H, 13C, and 19F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25°C exist largely as an equilibrium among several rapidly interconverting twisted Möbius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or Möbius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100°C in THF, these rapid interconversions among Möbius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a Möbius conformation. Detailed analyses of the solid-state Möbius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic π-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable Möbius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.

AB - meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by 1H, 13C, and 19F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25°C exist largely as an equilibrium among several rapidly interconverting twisted Möbius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or Möbius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100°C in THF, these rapid interconversions among Möbius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a Möbius conformation. Detailed analyses of the solid-state Möbius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic π-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable Möbius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.

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