| Автор | Hamada, Taisuke |
| Автор | Ohtsuka, Hiroshi |
| Автор | Sakaki, Shigeyoshi |
| Дата выпуска | 2001 |
| dc.description | Deracemization of a racemic mixture of Î - and Î -[Co(acac)3] (acacâ =â acetylacetonate) took place with a chiral ruthenium(II) complex, Î -[Ru(menbpy)3]<sup>2+</sup> (menbpyâ =â 4,4â ²-bis{(1R,2S,5R)-(â )-menthoxycarbonyl}-2,2â ²-bipyridine), under visible light (420â <â λâ <â 470 nm) irradiation in the presence of either triethylamine or NaOH. The enantiomeric excess (e.e.) of Î -[Co(acac)3] was 28% in acetonitrileâ water (7â â ¶â 3 v/v; ionic strength (Iâ )â =â 0.1 mol dm<sup>â 3</sup> (KCl)) without acetylacetone and 38% with acetylacetone (50 mmol dm<sup>â 3</sup>) added to the solution. Quenching experiments on Î -*[Ru(menbpy)3]<sup>2+</sup> led to the conclusion that this deracemization occurs through combination of the preferential photo-reduction of Î -[Co(acac)3] by Î -*[Ru(menbpy)3]<sup>2+</sup> to afford [Co(acac)2] and the thermal oxidation of [Co(acac)2] by Î -[Ru(menbpy)3]<sup>3+</sup> to afford preferentially Î -[Co(acac)3]. The selectivity of deracemization remarkably depends on the solvent; the e.e. value is 51% in acetoneâ water (7â â ¶â 3 v/v), 38% in ethanolâ water (7â â ¶â 3 v/v), and 37% in DMFâ water (7â â ¶â 3 v/v). The e.e. value significantly decreases to 33% from 51% in acetoneâ water (7â â ¶â 3 v/v) when the KCl concentration is increased to 0.3 mol dm<sup>â 3</sup> from 0.1 mol dm<sup>â 3</sup>. When either KF or CH3CO2K is added to acetoneâ water (7â â ¶â 3 v/v) instead of KCl the deracemization proceeds much more rapidly without decrease of the e.e. value (â 50%). These counter anion effects are interpreted in terms that the reduction potential of [Co(acac)3] becomes more negative by addition of either F<sup>â </sup> or CH3CO2<sup>â </sup>. |
| Формат | application.pdf |
| Издатель | Royal Society of Chemistry |
| Название | Novel photo-induced deracemization of [Co(acac)3] (acacâ =â acetylacetonate) with a chiral ruthenium(II) complex, Î -[Ru(menbpy)3]<sup>2+</sup> (menbpyâ =â 4,4â ²-bis{(1R,2S,5R)-(â )-menthoxycarbonyl}-2,2â ²-bipyridine). Reaction mechanism and significant effects of solvent and anionâ Electronic supplementary information (ESI) available: absorption and CD spectral changes of the reaction solution. See http://www.rsc.org/suppdata/dt/b0/b009124n/ |
| Тип | ART |
| Журнал | Dalton Transactions |
| Первая страница | 928 |
| Последняя страница | 934 |
| Аффилиация | Hamada Taisuke; Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University |
| Аффилиация | Ohtsuka Hiroshi; Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University |
| Аффилиация | Sakaki Shigeyoshi; Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University |
| Выпуск | 6 |
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