Tetraphenylporphyrin molecules containing heteroatoms other than nitrogen. 7. Emission and electronic structure of rings containing sulfur and selenium

Rodney L. Hill, Martin Gouterman, Abraham Ulman

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Abstract

We report on S and Se substituted tetraphenylporphyrins, where S and/or Se replace the central NH groups. S 2TPP shows fluorescence with λ max = 705 nm, lifetime 1.3 ns, and quantum yield φ f = 0.01. No phosphorescence is observed at 77 K in a solvent with 20% ethyl iodide. The acid dication of S 2TPP also fluoresces with λ max = 766 nm, lifetime 0.49 ns, and quantum yield φ f = 0.11. However, SSeTPP and Se 2TPP show no emission nor do their acid dications. Iterative extended Hückel (IEH) calculations predict an allowed charge-transfer (CT) transition Se(σ*) → π* at much lower energy than the analogous S(σ*) → π*. The lack of fluorescence is attributed to this transition occurring at lower energy than the π → π*. Curve fitting of the lowest energy optical absorption bands in H 2TPP, S 2TPP, SSeTPP, and Se 2TPP reveals that the Se-containing compounds have an extra band in the long-wavelength tail with λ max = 715 nm (Se 2TPP) and 705 nm (SSeTPP) that we attribute to the charge-transfer transition. Analysis of the IEH bond orders shows that contracted outer-valence d orbitals must be included to explain the cross-ring bonding, which increases in the order S-S < S-Se < Se-Se. The calculations raise the possibility that, while S 2TPP + is a π radical, Se 2TPP + may be either a π or a Se(σ*) radical.

Original languageEnglish (US)
Pages (from-to)1450-1455
Number of pages6
JournalInorganic Chemistry
Volume21
Issue number4
StatePublished - 1982

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Quantum yield
Selenium
selenium
Sulfur
Electronic structure
Charge transfer
Nitrogen
sulfur
Fluorescence
electronic structure
nitrogen
Phosphorescence
Molecules
Acids
rings
Curve fitting
Iodides
charge transfer
Light absorption
molecules

ASJC Scopus subject areas

  • Inorganic Chemistry

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Tetraphenylporphyrin molecules containing heteroatoms other than nitrogen. 7. Emission and electronic structure of rings containing sulfur and selenium. / Hill, Rodney L.; Gouterman, Martin; Ulman, Abraham.

In: Inorganic Chemistry, Vol. 21, No. 4, 1982, p. 1450-1455.

Research output: Contribution to journalArticle

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abstract = "We report on S and Se substituted tetraphenylporphyrins, where S and/or Se replace the central NH groups. S 2TPP shows fluorescence with λ max = 705 nm, lifetime 1.3 ns, and quantum yield φ f = 0.01. No phosphorescence is observed at 77 K in a solvent with 20{\%} ethyl iodide. The acid dication of S 2TPP also fluoresces with λ max = 766 nm, lifetime 0.49 ns, and quantum yield φ f = 0.11. However, SSeTPP and Se 2TPP show no emission nor do their acid dications. Iterative extended H{\"u}ckel (IEH) calculations predict an allowed charge-transfer (CT) transition Se(σ*) → π* at much lower energy than the analogous S(σ*) → π*. The lack of fluorescence is attributed to this transition occurring at lower energy than the π → π*. Curve fitting of the lowest energy optical absorption bands in H 2TPP, S 2TPP, SSeTPP, and Se 2TPP reveals that the Se-containing compounds have an extra band in the long-wavelength tail with λ max = 715 nm (Se 2TPP) and 705 nm (SSeTPP) that we attribute to the charge-transfer transition. Analysis of the IEH bond orders shows that contracted outer-valence d orbitals must be included to explain the cross-ring bonding, which increases in the order S-S < S-Se < Se-Se. The calculations raise the possibility that, while S 2TPP + is a π radical, Se 2TPP + may be either a π or a Se(σ*) radical.",
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N2 - We report on S and Se substituted tetraphenylporphyrins, where S and/or Se replace the central NH groups. S 2TPP shows fluorescence with λ max = 705 nm, lifetime 1.3 ns, and quantum yield φ f = 0.01. No phosphorescence is observed at 77 K in a solvent with 20% ethyl iodide. The acid dication of S 2TPP also fluoresces with λ max = 766 nm, lifetime 0.49 ns, and quantum yield φ f = 0.11. However, SSeTPP and Se 2TPP show no emission nor do their acid dications. Iterative extended Hückel (IEH) calculations predict an allowed charge-transfer (CT) transition Se(σ*) → π* at much lower energy than the analogous S(σ*) → π*. The lack of fluorescence is attributed to this transition occurring at lower energy than the π → π*. Curve fitting of the lowest energy optical absorption bands in H 2TPP, S 2TPP, SSeTPP, and Se 2TPP reveals that the Se-containing compounds have an extra band in the long-wavelength tail with λ max = 715 nm (Se 2TPP) and 705 nm (SSeTPP) that we attribute to the charge-transfer transition. Analysis of the IEH bond orders shows that contracted outer-valence d orbitals must be included to explain the cross-ring bonding, which increases in the order S-S < S-Se < Se-Se. The calculations raise the possibility that, while S 2TPP + is a π radical, Se 2TPP + may be either a π or a Se(σ*) radical.

AB - We report on S and Se substituted tetraphenylporphyrins, where S and/or Se replace the central NH groups. S 2TPP shows fluorescence with λ max = 705 nm, lifetime 1.3 ns, and quantum yield φ f = 0.01. No phosphorescence is observed at 77 K in a solvent with 20% ethyl iodide. The acid dication of S 2TPP also fluoresces with λ max = 766 nm, lifetime 0.49 ns, and quantum yield φ f = 0.11. However, SSeTPP and Se 2TPP show no emission nor do their acid dications. Iterative extended Hückel (IEH) calculations predict an allowed charge-transfer (CT) transition Se(σ*) → π* at much lower energy than the analogous S(σ*) → π*. The lack of fluorescence is attributed to this transition occurring at lower energy than the π → π*. Curve fitting of the lowest energy optical absorption bands in H 2TPP, S 2TPP, SSeTPP, and Se 2TPP reveals that the Se-containing compounds have an extra band in the long-wavelength tail with λ max = 715 nm (Se 2TPP) and 705 nm (SSeTPP) that we attribute to the charge-transfer transition. Analysis of the IEH bond orders shows that contracted outer-valence d orbitals must be included to explain the cross-ring bonding, which increases in the order S-S < S-Se < Se-Se. The calculations raise the possibility that, while S 2TPP + is a π radical, Se 2TPP + may be either a π or a Se(σ*) radical.

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