Repozytorium Uniwersytetu Jagiellońskiego
Kinetic and mechanistic studies on the reaction of nitric oxide with a water-soluble octa-anionic iron(III) porphyrin complex
Kinetic and mechanistic studies on the reaction of ...
Opis pozycji
| tytuł: | Kinetic and mechanistic studies on the reaction of nitric oxide with a water-soluble octa-anionic iron(III) porphyrin complex |
| autor: | Jee Joo-Eun, Eigler Siegfried, Hampel Frank, Jux Norbert, Wolak Maria, Zahl Achim, Stochel Grażyna  , Eldik Rudi van |
| tytuł czasopisma: | Inorganic Chemistry |
| tom: | 44 |
| numer: | 22 |
| data wydania: | 2005 |
| strony: | 7717-7731 |
| ISSN: |
0020-1669 |
| eISSN: |
1520-510X |
| DOI: | |
| język: | angielski |
| język czasopisma: | angielski |
| abstrakt w j. angielskim: | The polyanionic water-soluble and non-μ-oxo-dimer-forming iron porphyrin iron(III) 54,104,154,204-tetra-tert-butyl-52,56,152,156-tetrakis[2,2-bis(carboxylato)ethyl]-5,10,15,20-tetraphenylporphyrin, (P8-)FeIII (1), was synthesized as an octasodium salt by applying well-established porphyrin and organic chemistry procedures to bromomethylated precursor porphyrins and characterized by standard techniques such as UV−vis and 1H NMR spectroscopy. A single pKa1 value of 9.26 was determined for the deprotonation of coordinated water in (P8-)FeIII(H2O)2 (1-H2O) present in aqueous solution at pH <9. The porphyrin complex reversibly binds NO in aqueous solution to give the mononitrosyl adduct, (P8-)FeII(NO+)(L), where L = H2O or OH-. The kinetics of the binding and release of NO was studied as a function of pH, temperature, and pressure by stopped-flow and laser flash photolysis techniques. The diaqua-ligated form of the porphyrin complex binds and releases NO according to a dissociative interchange mechanism based on the positive values of the activation parameters ΔS⧧ and ΔV⧧ for the “on” and “off” reactions. The rate constant kon = 6.2 × 104 M-1 s-1 (24 °C), determined for NO binding to the monohydroxo-ligated (P8-)FeIII(OH) (1-OH) present in solution at pH >9, is markedly lower than the corresponding value measured for 1-H2O at lower pH (kon = 8.2 × 105 M-1 s-1, 24 °C, pH 7). The observed decrease in the reactivity is contradictory to that expected for the diaqua- and monohydroxo-ligated forms of the iron(III) complex and is accounted for in terms of a mechanistic changeover observed for 1-H2O and 1-OH in their reactions with NO. The mechanistic interpretation offered is further substantiated by the results of water-exchange studies performed on the polyanionic porphyrin complex as a function of pH, temperature, and pressure. |
| wydział:instytut/zakład/katedra: | Wydział Chemii : Zakład Chemii Nieorganicznej |
| typ: | artykuł w czasopiśmie |
| podtyp: | artykuł |
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