One-electron redox kinetics of aqueous transition metal couples Zn2+/+, Co2+/+, and Ni2+/+ using pulse radiolysis
| Autor: | David M. Bartels, Kotchaphan Kanjana, Alexandra Lisovskaya |
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| Rok vydání: | 2020 |
| Předmět: |
Aqueous solution
Order of reaction 010304 chemical physics Chemistry Radical Kinetics General Physics and Astronomy 010402 general chemistry 01 natural sciences Redox 0104 chemical sciences Reaction rate constant Transition metal 0103 physical sciences Radiolysis Physical chemistry Physical and Theoretical Chemistry |
| Zdroj: | Physical Chemistry Chemical Physics. 22:19046-19058 |
| ISSN: | 1463-9084 1463-9076 |
| DOI: | 10.1039/d0cp03214j |
| Popis: | The one-electron redox potentials for aqueous metal couples Co2+/+ and Ni2+/+ have been investigated by using pulse radiolysis using their reactions with a series of reference compounds to establish the most positive upper limits of E0. Experiments with Zn+ were also carried out to confirm the characteristic shape of the expected reduction kinetics. Both formate ions and t-BuOH were employed to scavenge ˙OH radicals and ˙H atoms. Kinetics and fitted first and second order reaction rates have been reported for reactions with methyl viologen, fluorescein, Ru(NH3)63+, Co(en)32+, Co(sepulcrate)3+, Ru(bpy)32+, Cr(bpy)33+, and Ni(Me6[14]4,11-dieneN4)2+. Previous work demonstrated that both Co2+ and Ni2+ can be reduced by CO2˙− radicals, giving a negative E0 limit of −1.9 V vs. SHE. A definite reaction of Ni+ with fluorescein di-anions provides a new upper limit of the Ni2+/+ couple as −0.906 V vs. SHE. The reaction of Co+ with Ru(bpy)32+ has been confirmed, giving E0 = −1.3 V vs. SHE as a rigorous upper limit of the Co2+/+ couple. In the case of Co2+/+, kinetics were complicated by a self-catalyzed metal clustering phenomenon. Initiation rate constants of this process have also been reported. |
| Databáze: | OpenAIRE |
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