Investigation of the Lowest Electronic States of Osmium(II) Tetratolylporphyrins: Photophysics of Metalloporphyrin (d,π*) Charge Transfer States

Steve Gentemann, Jennifer Albaneze, Ramon Garcia-Ferrer, Spencer Knapp, Joseph A. Potenza, Harvey J. Schugar, Dewey Holten

Research output: Contribution to journalArticle

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Abstract

The nature of the lowest excited states of a series of osmium(II) porphyrins has been investigated using static and time-resolved emission spectroscopy and ultrafast transient absorption measurements. It is found that a metalto- ring3(d,π*) charge transfer excited state is the lowest excited state of the OsIIP(CO)(L) and OsIIP(L)2 complexes, where the porphyrin macrocycle (P) is either tetratolyl- or octaethylporphyrin and the axial ligand L is a σ-donor such as pyridine. Previous studies on OsTTP(CO)(py) had led to the assignment of the lowest excited state as the 3(π,π*) state of the porphyrin ring. The results on the OsII porphyrins can be contrasted with those found previously for the analogous RuII porphyrins, in which the lowest excited state was found to switch from 3(π,π*) in the RuP(CO)(L) complexes to 3(d,π*) in the RuP(L)2 compounds. The studies further establish the electronic origin of the red-region features in the absorption spectra of metalloporphyrin 3(π,π*) and 3(d,π*) excited states. The combined results demonstrate the critical role played by π-accepting and σ-donating axial ligands in controlling the nature of the lowest excited states, the electronic properties, and excited state dynamics of the biologically-relevant d6 metalloporphyrins.

Original languageEnglish (US)
Pages (from-to)281-289
Number of pages9
JournalJournal of the American Chemical Society
Volume116
Issue number1
DOIs
StatePublished - Jan 1 1994

Fingerprint

Metalloporphyrins
Osmium
Porphyrins
Electronic states
Excited states
Charge transfer
Carbon Monoxide
Ligands
Spectrum Analysis
Emission spectroscopy
Electronic properties
Pyridine
Absorption spectra
Switches

All Science Journal Classification (ASJC) codes

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

Cite this

Gentemann, Steve ; Albaneze, Jennifer ; Garcia-Ferrer, Ramon ; Knapp, Spencer ; Potenza, Joseph A. ; Schugar, Harvey J. ; Holten, Dewey. / Investigation of the Lowest Electronic States of Osmium(II) Tetratolylporphyrins : Photophysics of Metalloporphyrin (d,π*) Charge Transfer States. In: Journal of the American Chemical Society. 1994 ; Vol. 116, No. 1. pp. 281-289.
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abstract = "The nature of the lowest excited states of a series of osmium(II) porphyrins has been investigated using static and time-resolved emission spectroscopy and ultrafast transient absorption measurements. It is found that a metalto- ring3(d,π*) charge transfer excited state is the lowest excited state of the OsIIP(CO)(L) and OsIIP(L)2 complexes, where the porphyrin macrocycle (P) is either tetratolyl- or octaethylporphyrin and the axial ligand L is a σ-donor such as pyridine. Previous studies on OsTTP(CO)(py) had led to the assignment of the lowest excited state as the 3(π,π*) state of the porphyrin ring. The results on the OsII porphyrins can be contrasted with those found previously for the analogous RuII porphyrins, in which the lowest excited state was found to switch from 3(π,π*) in the RuP(CO)(L) complexes to 3(d,π*) in the RuP(L)2 compounds. The studies further establish the electronic origin of the red-region features in the absorption spectra of metalloporphyrin 3(π,π*) and 3(d,π*) excited states. The combined results demonstrate the critical role played by π-accepting and σ-donating axial ligands in controlling the nature of the lowest excited states, the electronic properties, and excited state dynamics of the biologically-relevant d6 metalloporphyrins.",
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Investigation of the Lowest Electronic States of Osmium(II) Tetratolylporphyrins : Photophysics of Metalloporphyrin (d,π*) Charge Transfer States. / Gentemann, Steve; Albaneze, Jennifer; Garcia-Ferrer, Ramon; Knapp, Spencer; Potenza, Joseph A.; Schugar, Harvey J.; Holten, Dewey.

In: Journal of the American Chemical Society, Vol. 116, No. 1, 01.01.1994, p. 281-289.

Research output: Contribution to journalArticle

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T1 - Investigation of the Lowest Electronic States of Osmium(II) Tetratolylporphyrins

T2 - Photophysics of Metalloporphyrin (d,π*) Charge Transfer States

AU - Gentemann, Steve

AU - Albaneze, Jennifer

AU - Garcia-Ferrer, Ramon

AU - Knapp, Spencer

AU - Potenza, Joseph A.

AU - Schugar, Harvey J.

AU - Holten, Dewey

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Y1 - 1994/1/1

N2 - The nature of the lowest excited states of a series of osmium(II) porphyrins has been investigated using static and time-resolved emission spectroscopy and ultrafast transient absorption measurements. It is found that a metalto- ring3(d,π*) charge transfer excited state is the lowest excited state of the OsIIP(CO)(L) and OsIIP(L)2 complexes, where the porphyrin macrocycle (P) is either tetratolyl- or octaethylporphyrin and the axial ligand L is a σ-donor such as pyridine. Previous studies on OsTTP(CO)(py) had led to the assignment of the lowest excited state as the 3(π,π*) state of the porphyrin ring. The results on the OsII porphyrins can be contrasted with those found previously for the analogous RuII porphyrins, in which the lowest excited state was found to switch from 3(π,π*) in the RuP(CO)(L) complexes to 3(d,π*) in the RuP(L)2 compounds. The studies further establish the electronic origin of the red-region features in the absorption spectra of metalloporphyrin 3(π,π*) and 3(d,π*) excited states. The combined results demonstrate the critical role played by π-accepting and σ-donating axial ligands in controlling the nature of the lowest excited states, the electronic properties, and excited state dynamics of the biologically-relevant d6 metalloporphyrins.

AB - The nature of the lowest excited states of a series of osmium(II) porphyrins has been investigated using static and time-resolved emission spectroscopy and ultrafast transient absorption measurements. It is found that a metalto- ring3(d,π*) charge transfer excited state is the lowest excited state of the OsIIP(CO)(L) and OsIIP(L)2 complexes, where the porphyrin macrocycle (P) is either tetratolyl- or octaethylporphyrin and the axial ligand L is a σ-donor such as pyridine. Previous studies on OsTTP(CO)(py) had led to the assignment of the lowest excited state as the 3(π,π*) state of the porphyrin ring. The results on the OsII porphyrins can be contrasted with those found previously for the analogous RuII porphyrins, in which the lowest excited state was found to switch from 3(π,π*) in the RuP(CO)(L) complexes to 3(d,π*) in the RuP(L)2 compounds. The studies further establish the electronic origin of the red-region features in the absorption spectra of metalloporphyrin 3(π,π*) and 3(d,π*) excited states. The combined results demonstrate the critical role played by π-accepting and σ-donating axial ligands in controlling the nature of the lowest excited states, the electronic properties, and excited state dynamics of the biologically-relevant d6 metalloporphyrins.

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