pH-Driven Mechanistic Switching from Electron Transfer to Energy Transfer between [Ru(bpy) 3 ] 2+ and Ferrocene Derivatives.

Autor: Drolen C; Department of Chemistry , Amherst College , Merrill Science Building , Amherst , Massachusetts 01002 , United States., Conklin E; Department of Chemistry , Amherst College , Merrill Science Building , Amherst , Massachusetts 01002 , United States., Hetterich SJ; Department of Chemistry , Amherst College , Merrill Science Building , Amherst , Massachusetts 01002 , United States., Krishnamurthy A; Department of Chemistry , Amherst College , Merrill Science Building , Amherst , Massachusetts 01002 , United States., Andrade GA; Department of Chemistry and Biochemistry, Brown Laboratory , University of Delaware , Newark , Delaware 19716 , United States., Dimeglio JL; Department of Chemistry and Biochemistry, Brown Laboratory , University of Delaware , Newark , Delaware 19716 , United States., Martin MI; Department of Chemistry and Biochemistry, Brown Laboratory , University of Delaware , Newark , Delaware 19716 , United States., Tran LK; Department of Chemistry and Biochemistry, Brown Laboratory , University of Delaware , Newark , Delaware 19716 , United States., Yap GPA; Department of Chemistry and Biochemistry, Brown Laboratory , University of Delaware , Newark , Delaware 19716 , United States., Rosenthal J; Department of Chemistry and Biochemistry, Brown Laboratory , University of Delaware , Newark , Delaware 19716 , United States., Young ER; Department of Chemistry , Amherst College , Merrill Science Building , Amherst , Massachusetts 01002 , United States.; Department of Chemistry , Lehigh University , Seeley G. Mudd Building, Bethlehem , Pennsylvania , 18015 , United States.
Jazyk: angličtina
Zdroj: Journal of the American Chemical Society [J Am Chem Soc] 2018 Aug 15; Vol. 140 (32), pp. 10169-10178. Date of Electronic Publication: 2018 Aug 02.
DOI: 10.1021/jacs.8b03933
Abstrakt: The metal-to-ligand charge transfer excited states of [Ru(bpy) 3 ] 2+ (bpy = 2,2'-bipyridine) may be deactivated via energy transfer or electron transfer with ferrocene derivatives in aqueous conditions. Stern-Volmer quenching analysis revealed that the rate constant for [Ru(bpy) 3 ] 2+ excited-state quenching depends on solution pH when a ferrocenyl-amidinium derivative (Fc-am) containing a proton-responsive functionality tethered to the ferrocene center was present. By contrast, the rate constant with which the [Ru(bpy) 3 ] 2+ excited state is quenched by an analogous ferrocene derivative (ferrocenyl-trimethylammonium, Fc-mam) that lacks a protonic group does not depend on pH. These results show that the presence (or absence) of a readily transferrable proton modulates quenching rate constants in bimolecular events involving [Ru(bpy) 3 ] 2+ and ferrocene. More surprisingly, transient absorption spectroscopy reveals that the mechanism by which the [Ru(bpy) 3 ] 2+ excited state is quenched by Fc-am appears to be modulated by solution proton availability, switching from energy transfer at low pH when Fc-am is protonated, to electron transfer at high pH when Fc-am is deprotonated. The mechanistic switching that is observed for this system cannot be aptly explained using a simple driving force dependence argument, suggesting that more subtle factors dictate the pathway by which the [Ru(bpy) 3 ] 2+ excited state is deactivated by ferrocene in aqueous solutions.
Databáze: MEDLINE
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