Photophysics and photochemistry of water-soluble, sitting-atop bis-thallium(1) 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin

Zsolt Valicsek, O. Horváth, Kenneth L. Stevenson

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

In aqueous solutions, thallium(I) ions and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin form a kinetically labile metalloporphyrin of 2 : 1 composition (Tl2P4-). The formation constant of this sitting-atop (SAT) complex is relatively low (β2/[H+]2 = 3.55 × 103 M-2 at pH = 7), due to the large size and rather small charge of Tl+. As a consequence of the considerably weak metal-ligand interaction in this system, the 1 : 1 species does not appear in detectable concentration. Both the absorption and the emission properties of the Tl2P4- complex are characteristic for the typical SAT metalloporphyrins. Compared to the corresponding values of the free-base porphyrin, the diminished fluorescence quantum efficiency (Qfl = 0.0131 vs. 0.056) of Tl2P4- can be accounted for by the heavy-atom effect, while the larger Stokes shift (442 vs. 282 cm-1) indicates a stronger distortion of the ligand plane. Both Soret- and Q-band irradiations of the Tl2,P4- complex lead to the degradation of the porphyrin with quantum yields of magnitude 3 × 10-4. The primary photochemical step in this process is ligand-to-metal charge transfer reaction, which is unusual for normal (coplanar) metalloporphyrins. In the case of SAT complexes, the kinetic lability facilitates the separation of the primary redox products, followed by an irreversible ring-opening of the oxidized porphyrin. Photoinduced electron ejection as a considerable step in the degradation mechanism could be ruled out.

Original languageEnglish
Pages (from-to)669-673
Number of pages5
JournalPhotochemical and Photobiological Sciences
Volume3
Issue number7
DOIs
Publication statusPublished - Jul 2004

Fingerprint

Metalloporphyrins
Photochemistry
Thallium
Photochemical reactions
Porphyrins
thallium
porphyrins
photochemical reactions
Ligands
Water
Metals
water
ligands
Degradation
Quantum yield
degradation
Quantum efficiency
Oxidation-Reduction
Charge transfer
Fluorescence

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Cell Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Biophysics

Cite this

Photophysics and photochemistry of water-soluble, sitting-atop bis-thallium(1) 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin. / Valicsek, Zsolt; Horváth, O.; Stevenson, Kenneth L.

In: Photochemical and Photobiological Sciences, Vol. 3, No. 7, 07.2004, p. 669-673.

Research output: Contribution to journalArticle

@article{dc1f041094ad44b1afa3b82e9f832109,
title = "Photophysics and photochemistry of water-soluble, sitting-atop bis-thallium(1) 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin",
abstract = "In aqueous solutions, thallium(I) ions and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin form a kinetically labile metalloporphyrin of 2 : 1 composition (Tl2P4-). The formation constant of this sitting-atop (SAT) complex is relatively low (β2/[H+]2 = 3.55 × 103 M-2 at pH = 7), due to the large size and rather small charge of Tl+. As a consequence of the considerably weak metal-ligand interaction in this system, the 1 : 1 species does not appear in detectable concentration. Both the absorption and the emission properties of the Tl2P4- complex are characteristic for the typical SAT metalloporphyrins. Compared to the corresponding values of the free-base porphyrin, the diminished fluorescence quantum efficiency (Qfl = 0.0131 vs. 0.056) of Tl2P4- can be accounted for by the heavy-atom effect, while the larger Stokes shift (442 vs. 282 cm-1) indicates a stronger distortion of the ligand plane. Both Soret- and Q-band irradiations of the Tl2,P4- complex lead to the degradation of the porphyrin with quantum yields of magnitude 3 × 10-4. The primary photochemical step in this process is ligand-to-metal charge transfer reaction, which is unusual for normal (coplanar) metalloporphyrins. In the case of SAT complexes, the kinetic lability facilitates the separation of the primary redox products, followed by an irreversible ring-opening of the oxidized porphyrin. Photoinduced electron ejection as a considerable step in the degradation mechanism could be ruled out.",
author = "Zsolt Valicsek and O. Horv{\'a}th and Stevenson, {Kenneth L.}",
year = "2004",
month = "7",
doi = "10.1039/b405105j",
language = "English",
volume = "3",
pages = "669--673",
journal = "Photochemical and Photobiological Sciences",
issn = "1474-905X",
publisher = "Royal Society of Chemistry",
number = "7",

}

TY - JOUR

T1 - Photophysics and photochemistry of water-soluble, sitting-atop bis-thallium(1) 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin

AU - Valicsek, Zsolt

AU - Horváth, O.

AU - Stevenson, Kenneth L.

PY - 2004/7

Y1 - 2004/7

N2 - In aqueous solutions, thallium(I) ions and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin form a kinetically labile metalloporphyrin of 2 : 1 composition (Tl2P4-). The formation constant of this sitting-atop (SAT) complex is relatively low (β2/[H+]2 = 3.55 × 103 M-2 at pH = 7), due to the large size and rather small charge of Tl+. As a consequence of the considerably weak metal-ligand interaction in this system, the 1 : 1 species does not appear in detectable concentration. Both the absorption and the emission properties of the Tl2P4- complex are characteristic for the typical SAT metalloporphyrins. Compared to the corresponding values of the free-base porphyrin, the diminished fluorescence quantum efficiency (Qfl = 0.0131 vs. 0.056) of Tl2P4- can be accounted for by the heavy-atom effect, while the larger Stokes shift (442 vs. 282 cm-1) indicates a stronger distortion of the ligand plane. Both Soret- and Q-band irradiations of the Tl2,P4- complex lead to the degradation of the porphyrin with quantum yields of magnitude 3 × 10-4. The primary photochemical step in this process is ligand-to-metal charge transfer reaction, which is unusual for normal (coplanar) metalloporphyrins. In the case of SAT complexes, the kinetic lability facilitates the separation of the primary redox products, followed by an irreversible ring-opening of the oxidized porphyrin. Photoinduced electron ejection as a considerable step in the degradation mechanism could be ruled out.

AB - In aqueous solutions, thallium(I) ions and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin form a kinetically labile metalloporphyrin of 2 : 1 composition (Tl2P4-). The formation constant of this sitting-atop (SAT) complex is relatively low (β2/[H+]2 = 3.55 × 103 M-2 at pH = 7), due to the large size and rather small charge of Tl+. As a consequence of the considerably weak metal-ligand interaction in this system, the 1 : 1 species does not appear in detectable concentration. Both the absorption and the emission properties of the Tl2P4- complex are characteristic for the typical SAT metalloporphyrins. Compared to the corresponding values of the free-base porphyrin, the diminished fluorescence quantum efficiency (Qfl = 0.0131 vs. 0.056) of Tl2P4- can be accounted for by the heavy-atom effect, while the larger Stokes shift (442 vs. 282 cm-1) indicates a stronger distortion of the ligand plane. Both Soret- and Q-band irradiations of the Tl2,P4- complex lead to the degradation of the porphyrin with quantum yields of magnitude 3 × 10-4. The primary photochemical step in this process is ligand-to-metal charge transfer reaction, which is unusual for normal (coplanar) metalloporphyrins. In the case of SAT complexes, the kinetic lability facilitates the separation of the primary redox products, followed by an irreversible ring-opening of the oxidized porphyrin. Photoinduced electron ejection as a considerable step in the degradation mechanism could be ruled out.

UR - http://www.scopus.com/inward/record.url?scp=4344646384&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=4344646384&partnerID=8YFLogxK

U2 - 10.1039/b405105j

DO - 10.1039/b405105j

M3 - Article

VL - 3

SP - 669

EP - 673

JO - Photochemical and Photobiological Sciences

JF - Photochemical and Photobiological Sciences

SN - 1474-905X

IS - 7

ER -