Synthesis and Properties of Tetraphenylporphyrin Molecules Containing Heteroatoms Other than Nitrogen. 5. High Resolution Nuclear Magnetic Resonance Studies of Inner and Outer Aromaticity

Abraham Ulman, Manassen Joost, Frolow Felix, Rabinovich Dov

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Abstract

When the two NH groups in tetraphenylporphyrin are replaced by the group 6A heteroatoms S, Se, and Te, bonding interactions within the porphyrin core are found, as is apparent from X-ray analysis results. Because of these interactions, changes in the inner and outer aromatic pathways occur, which are expressed in the chemical shifts of the hydrogen atoms at the periphery of the molecule. The bonding interactions within the core are disrupted by either protonation or complexation, and this finds its expression in the chemical shifts in a consistent way. If two different heteroatoms are introduced, or when the p-phenyl hydrogens are substituted in such a way that two phenyl groups carry substituents of different electronic properties, charge transfer occurs between the heteroatoms. This charge transfer changes the inner aromatic pathway, which influences the chemical shift. These shifts relate linearly to the Hammett constant of the substituents. Starting from these results, the concept is developed that the interaction between the heteroatoms acts as an electron drain on the π electrons and especially on the pyrrolenine-N nonbonding electrons. This causes an increased contribution of the 20-membered, extended outer aromaticity Kekule structures.

Original languageEnglish (US)
Pages (from-to)7055-7059
Number of pages5
JournalJournal of the American Chemical Society
Volume101
Issue number23
DOIs
StatePublished - Sep 1 1979

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Chemical shift
Magnetic Resonance Spectroscopy
Nitrogen
Nuclear magnetic resonance
Electrons
Molecules
Charge transfer
Hydrogen
Protonation
Porphyrins
X ray analysis
Complexation
Electronic properties
X-Rays
Atoms
tetraphenylporphyrin

ASJC Scopus subject areas

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

Cite this

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title = "Synthesis and Properties of Tetraphenylporphyrin Molecules Containing Heteroatoms Other than Nitrogen. 5. High Resolution Nuclear Magnetic Resonance Studies of Inner and Outer Aromaticity",
abstract = "When the two NH groups in tetraphenylporphyrin are replaced by the group 6A heteroatoms S, Se, and Te, bonding interactions within the porphyrin core are found, as is apparent from X-ray analysis results. Because of these interactions, changes in the inner and outer aromatic pathways occur, which are expressed in the chemical shifts of the hydrogen atoms at the periphery of the molecule. The bonding interactions within the core are disrupted by either protonation or complexation, and this finds its expression in the chemical shifts in a consistent way. If two different heteroatoms are introduced, or when the p-phenyl hydrogens are substituted in such a way that two phenyl groups carry substituents of different electronic properties, charge transfer occurs between the heteroatoms. This charge transfer changes the inner aromatic pathway, which influences the chemical shift. These shifts relate linearly to the Hammett constant of the substituents. Starting from these results, the concept is developed that the interaction between the heteroatoms acts as an electron drain on the π electrons and especially on the pyrrolenine-N nonbonding electrons. This causes an increased contribution of the 20-membered, extended outer aromaticity Kekule structures.",
author = "Abraham Ulman and Manassen Joost and Frolow Felix and Rabinovich Dov",
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T1 - Synthesis and Properties of Tetraphenylporphyrin Molecules Containing Heteroatoms Other than Nitrogen. 5. High Resolution Nuclear Magnetic Resonance Studies of Inner and Outer Aromaticity

AU - Ulman, Abraham

AU - Joost, Manassen

AU - Felix, Frolow

AU - Dov, Rabinovich

PY - 1979/9/1

Y1 - 1979/9/1

N2 - When the two NH groups in tetraphenylporphyrin are replaced by the group 6A heteroatoms S, Se, and Te, bonding interactions within the porphyrin core are found, as is apparent from X-ray analysis results. Because of these interactions, changes in the inner and outer aromatic pathways occur, which are expressed in the chemical shifts of the hydrogen atoms at the periphery of the molecule. The bonding interactions within the core are disrupted by either protonation or complexation, and this finds its expression in the chemical shifts in a consistent way. If two different heteroatoms are introduced, or when the p-phenyl hydrogens are substituted in such a way that two phenyl groups carry substituents of different electronic properties, charge transfer occurs between the heteroatoms. This charge transfer changes the inner aromatic pathway, which influences the chemical shift. These shifts relate linearly to the Hammett constant of the substituents. Starting from these results, the concept is developed that the interaction between the heteroatoms acts as an electron drain on the π electrons and especially on the pyrrolenine-N nonbonding electrons. This causes an increased contribution of the 20-membered, extended outer aromaticity Kekule structures.

AB - When the two NH groups in tetraphenylporphyrin are replaced by the group 6A heteroatoms S, Se, and Te, bonding interactions within the porphyrin core are found, as is apparent from X-ray analysis results. Because of these interactions, changes in the inner and outer aromatic pathways occur, which are expressed in the chemical shifts of the hydrogen atoms at the periphery of the molecule. The bonding interactions within the core are disrupted by either protonation or complexation, and this finds its expression in the chemical shifts in a consistent way. If two different heteroatoms are introduced, or when the p-phenyl hydrogens are substituted in such a way that two phenyl groups carry substituents of different electronic properties, charge transfer occurs between the heteroatoms. This charge transfer changes the inner aromatic pathway, which influences the chemical shift. These shifts relate linearly to the Hammett constant of the substituents. Starting from these results, the concept is developed that the interaction between the heteroatoms acts as an electron drain on the π electrons and especially on the pyrrolenine-N nonbonding electrons. This causes an increased contribution of the 20-membered, extended outer aromaticity Kekule structures.

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