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

Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology
Zsolt ValicsekKenneth L Stevenson

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 (Tl(2)P(4-)). The formation constant of this sitting-atop (SAT) complex is relatively low (beta2/[H+]2= 3.55 x 10(3) 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 Tl(2)P(4-) 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 Tl(2)P(4-) 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 Tl(2)P(4-) complex lead to the degradation of the porphyrin with quantum yields of magnitude 3 x 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 complex...Continue Reading

References

Feb 6, 2002·Chembiochem : a European Journal of Chemical Biology·G Knör
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Oct 10, 2002·Chemical Reviews·Andrea MaldottiRossano Amadelli
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Citations

Mar 3, 2007·Journal of Biological Inorganic Chemistry : JBIC : a Publication of the Society of Biological Inorganic Chemistry·Róbert HuszánkOttó Horváth
Feb 23, 2005·Chemical Communications : Chem Comm·Róbert Huszánk, Ottó Horváth
Sep 25, 2012·Dalton Transactions : an International Journal of Inorganic Chemistry·Zsolt ValicsekOttó Horváth
Mar 9, 2011·Dalton Transactions : an International Journal of Inorganic Chemistry·Christopher M LemonBernard Boitrel
Apr 24, 2007·Journal of the American Chemical Society·John D HarrisDavid R Tyler

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