Eigler S, Hampel F, Jux N, Wolak M, Zahl A, van Eldik R (2005)
Publication Type: Journal article, Original article
Publication year: 2005
Original Authors: Jee J., Eigler S., Hampel F., Jux N., Wolak M., Zahl A., Stochel G., Van Eldik R.
Publisher: American Chemical Society
Book Volume: 44
Pages Range: 7717-7731
Journal Issue: 22
DOI: 10.1021/ic050924t
The polyanionic water-soluble and non-μ-oxo-dimer-forming iron porphyrin iron(III) 5,10,15,20-tetra- tert-butyl-5,5,15,15-tetrakis[2, 2-bis(carboxylato)ethyl]-5,10,15,20-tetraphenylporphyrin, (P) Fe (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 H NMR spectroscopy. A single pK value of 9.26 was determined for the deprotonation of coordinated water in (P)Fe (HO) (1-H2O) present in aqueous solution at pH <9. The porphyrin complex reversibly binds NO in aqueous solution to give the mononitrosyl adduct, (P)Fe(NO )(L), where L = HO 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 k = 6.2 × 10 M s (24°C), determined for NO binding to the monohydroxo-ligated (P)Fe(OH) (1-OH) present in solution at pH >9, is markedly lower than the corresponding value measured for 1-HO at lower pH (k = 8.2 × 10 M s , 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-HO 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. © 2005 American Chemical Society.
APA:
Eigler, S., Hampel, F., Jux, N., Wolak, M., Zahl, A., & van Eldik, R. (2005). Kinetic and mechanistic studies on the reaction of nitric oxide with a water-soluble octa-anionic iron(III) porphyrin complex. Inorganic Chemistry, 44(22), 7717-7731. https://dx.doi.org/10.1021/ic050924t
MLA:
Eigler, Siegfried, et al. "Kinetic and mechanistic studies on the reaction of nitric oxide with a water-soluble octa-anionic iron(III) porphyrin complex." Inorganic Chemistry 44.22 (2005): 7717-7731.
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