Kinetics for interaction of the thione unit in 4-thio-2'-deoxyuridine and 4-thiouridine 5'-monophosphate with rapidly reacting gold(III) complexes
(1998) In Journal of the Chemical Society. Dalton Transactions 1998. p.1687-1692- Abstract
- Reactions of 4-thio-2′-deoxyuridine d(s4U) and 4-thiouridine 5′-monophosphate s4UMP with trans-[AuY2Cl2]+/– (Y = CN– or NH3) have been investigated by conventional and high-pressure stopped-flow spectrophotometry in aqueous solution with 2.9 ⩽ pH ⩽ 7.0. For a given combination of metal complex and sulfur donor the observed second-order rate constants decreased with increasing pH. In the pH range 2.9 to 5.5 this decrease is mainly due to displacement of the pH-dependent equilibrium trans-[AuY2Cl2]+/– + H2O ⇌ trans-[AuY2Cl(OH)]+/– + Cl– + H+ and formation of an increasing fraction of the less reactive gold(III) hydroxo complex. The activation parameters ΔH ‡, ΔS ‡ and ΔV ‡ at pH 4.0 for substitution of chloride for thione at... (More)
- Reactions of 4-thio-2′-deoxyuridine d(s4U) and 4-thiouridine 5′-monophosphate s4UMP with trans-[AuY2Cl2]+/– (Y = CN– or NH3) have been investigated by conventional and high-pressure stopped-flow spectrophotometry in aqueous solution with 2.9 ⩽ pH ⩽ 7.0. For a given combination of metal complex and sulfur donor the observed second-order rate constants decreased with increasing pH. In the pH range 2.9 to 5.5 this decrease is mainly due to displacement of the pH-dependent equilibrium trans-[AuY2Cl2]+/– + H2O ⇌ trans-[AuY2Cl(OH)]+/– + Cl– + H+ and formation of an increasing fraction of the less reactive gold(III) hydroxo complex. The activation parameters ΔH ‡, ΔS ‡ and ΔV ‡ at pH 4.0 for substitution of chloride for thione at trans-[AuY2Cl2]+/– indicate an associative interchange process. When the thione-containing nucleotide reacts with the cation, steric and electrostatic interactions between the metal complex and the phosphate group oppose each other and the rate of the reaction of trans-[Au(NH3)2Cl2]+ with s4UMP is approximately the same as with d(s4U). Thus, the electrostatic outer-sphere interaction with a single phosphate group adjacent to the kinetically preferred binding site is not sufficient to induce a reactivity that significantly exceeds that of direct interaction between the thione and the rapidly reacting gold(III) centre. In contrast, reaction of trans-[Au(CN)2Cl2]– with s4UMP is significantly slower than with d(s4U), most likely due to the combined effect of electrostatic repulsion and steric blocking. (Less)
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- author
- Ericson, Anna LU ; Arthur, John C. ; Coleman, Robert S. ; Elding, Lars Ivar LU and Elmroth, Sofi LU
- organization
- publishing date
- 1998
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Inorganic chemistry, Gold(III) complexes, Thiones, Stopped-flow kinetics, Activation parameters, Reaction mechanism
- in
- Journal of the Chemical Society. Dalton Transactions
- volume
- 1998
- article number
- 7/08564H
- pages
- 6 pages
- publisher
- Royal Society of Chemistry
- external identifiers
-
- scopus:33748988510
- ISSN
- 1472-7773
- DOI
- 10.1039/A708564H
- language
- English
- LU publication?
- yes
- id
- 4cccb125-1157-42c6-887b-e93a586989ca
- date added to LUP
- 2016-12-18 19:01:20
- date last changed
- 2022-01-30 08:32:47
@article{4cccb125-1157-42c6-887b-e93a586989ca, abstract = {{Reactions of 4-thio-2′-deoxyuridine d(s4U) and 4-thiouridine 5′-monophosphate s4UMP with trans-[AuY2Cl2]+/– (Y = CN– or NH3) have been investigated by conventional and high-pressure stopped-flow spectrophotometry in aqueous solution with 2.9 ⩽ pH ⩽ 7.0. For a given combination of metal complex and sulfur donor the observed second-order rate constants decreased with increasing pH. In the pH range 2.9 to 5.5 this decrease is mainly due to displacement of the pH-dependent equilibrium trans-[AuY2Cl2]+/– + H2O ⇌ trans-[AuY2Cl(OH)]+/– + Cl– + H+ and formation of an increasing fraction of the less reactive gold(III) hydroxo complex. The activation parameters ΔH ‡, ΔS ‡ and ΔV ‡ at pH 4.0 for substitution of chloride for thione at trans-[AuY2Cl2]+/– indicate an associative interchange process. When the thione-containing nucleotide reacts with the cation, steric and electrostatic interactions between the metal complex and the phosphate group oppose each other and the rate of the reaction of trans-[Au(NH3)2Cl2]+ with s4UMP is approximately the same as with d(s4U). Thus, the electrostatic outer-sphere interaction with a single phosphate group adjacent to the kinetically preferred binding site is not sufficient to induce a reactivity that significantly exceeds that of direct interaction between the thione and the rapidly reacting gold(III) centre. In contrast, reaction of trans-[Au(CN)2Cl2]– with s4UMP is significantly slower than with d(s4U), most likely due to the combined effect of electrostatic repulsion and steric blocking.}}, author = {{Ericson, Anna and Arthur, John C. and Coleman, Robert S. and Elding, Lars Ivar and Elmroth, Sofi}}, issn = {{1472-7773}}, keywords = {{Inorganic chemistry; Gold(III) complexes; Thiones; Stopped-flow kinetics; Activation parameters; Reaction mechanism}}, language = {{eng}}, pages = {{1687--1692}}, publisher = {{Royal Society of Chemistry}}, series = {{Journal of the Chemical Society. Dalton Transactions}}, title = {{Kinetics for interaction of the thione unit in 4-thio-2'-deoxyuridine and 4-thiouridine 5'-monophosphate with rapidly reacting gold(III) complexes}}, url = {{http://dx.doi.org/10.1039/A708564H}}, doi = {{10.1039/A708564H}}, volume = {{1998}}, year = {{1998}}, }