Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates
Complexes of the [RuIII(edta)SR]n series, with SR- = deprotonated cysteine, N-acetylcysteine, 2-mercaptoethanol, glutathione and penicilamine, were prepared from [Ru(edta)H2O]- and the corresponding RSH thiols, at pH = 5.5. The complexes exhibit intense visible absorption bands at ca. 520 nm (ε ≅ 35...
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todo:paper_03404285_v23_n6_p657_Povse2023-10-03T15:25:35Z Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates Povse, V.G. Olabe, J.A. Complexes of the [RuIII(edta)SR]n series, with SR- = deprotonated cysteine, N-acetylcysteine, 2-mercaptoethanol, glutathione and penicilamine, were prepared from [Ru(edta)H2O]- and the corresponding RSH thiols, at pH = 5.5. The complexes exhibit intense visible absorption bands at ca. 520 nm (ε ≅ 3500 M-1 cm-1), associated with LMCT from the sulfur ligands bound to RuIII. The kinetics of the formation reactions were first order in [RuIII(edta)H2O]- and thiol reactants, with k1 values ca. 1-5 × 102 M-1 s-1 (25°C) for all the sulfur ligands except penicilamine, which reacted slower by a factor of 10. Activation parameters suggest an associative mechanism, as for the coordination of other S-and N-bound ligands to [RuIII(edta)H2O]-. A reactivity decrease is apparent at low and high pH's (ranges 1-3 and 8-10, respectively), associated with acid-base equilibria involving the less reactive [RuIII(Hedta)H2O] and [RuIII(edta)OH]2- species. A significant rate increase was found for cysteine and penicilamine at ca. pH = 8.0, because the thiol reactants deprotonate. The equilibrium constants for all the ligands showed that robust complexes were formed, with K = ca. 1 × 105 M-1 (25°C). The dissociation rate constants, k-1, were in the 10-3-10-4 s-1 range. The influence of nucleophilic and steric effects increasing and decreasing the formation rates, respectively, is discussed for the thiolate ligands, with adequate comparisons with other L species bound to [RuIII(edta)H2O]-. Fil:Povse, V.G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Olabe, J.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_03404285_v23_n6_p657_Povse |
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Universidad de Buenos Aires |
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I-28 |
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R-134 |
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| description |
Complexes of the [RuIII(edta)SR]n series, with SR- = deprotonated cysteine, N-acetylcysteine, 2-mercaptoethanol, glutathione and penicilamine, were prepared from [Ru(edta)H2O]- and the corresponding RSH thiols, at pH = 5.5. The complexes exhibit intense visible absorption bands at ca. 520 nm (ε ≅ 3500 M-1 cm-1), associated with LMCT from the sulfur ligands bound to RuIII. The kinetics of the formation reactions were first order in [RuIII(edta)H2O]- and thiol reactants, with k1 values ca. 1-5 × 102 M-1 s-1 (25°C) for all the sulfur ligands except penicilamine, which reacted slower by a factor of 10. Activation parameters suggest an associative mechanism, as for the coordination of other S-and N-bound ligands to [RuIII(edta)H2O]-. A reactivity decrease is apparent at low and high pH's (ranges 1-3 and 8-10, respectively), associated with acid-base equilibria involving the less reactive [RuIII(Hedta)H2O] and [RuIII(edta)OH]2- species. A significant rate increase was found for cysteine and penicilamine at ca. pH = 8.0, because the thiol reactants deprotonate. The equilibrium constants for all the ligands showed that robust complexes were formed, with K = ca. 1 × 105 M-1 (25°C). The dissociation rate constants, k-1, were in the 10-3-10-4 s-1 range. The influence of nucleophilic and steric effects increasing and decreasing the formation rates, respectively, is discussed for the thiolate ligands, with adequate comparisons with other L species bound to [RuIII(edta)H2O]-. |
| format |
JOUR |
| author |
Povse, V.G. Olabe, J.A. |
| spellingShingle |
Povse, V.G. Olabe, J.A. Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates |
| author_facet |
Povse, V.G. Olabe, J.A. |
| author_sort |
Povse, V.G. |
| title |
Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates |
| title_short |
Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates |
| title_full |
Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates |
| title_fullStr |
Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates |
| title_full_unstemmed |
Kinetics and mechanism of ligand interchange in the [RuIII(edta)L] complexes; L = Cysteine and related thiolates |
| title_sort |
kinetics and mechanism of ligand interchange in the [ruiii(edta)l] complexes; l = cysteine and related thiolates |
| url |
http://hdl.handle.net/20.500.12110/paper_03404285_v23_n6_p657_Povse |
| work_keys_str_mv |
AT povsevg kineticsandmechanismofligandinterchangeintheruiiiedtalcomplexeslcysteineandrelatedthiolates AT olabeja kineticsandmechanismofligandinterchangeintheruiiiedtalcomplexeslcysteineandrelatedthiolates |
| _version_ |
1807314958098104320 |