Mechanism of hydride donor generation using a Ru(II) complex containing an NAD+ model ligand: Pulse and steady-state radiolysis studies

Dmitry E. Polyansky, Diane Cabelli, James T. Muckerman, Takashi Fukushima, Koji Tanaka, Etsuko Fujita

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60 Citations (Scopus)

Abstract

The mechanistic pathways of formation of the NADH-like [Ru(bpy) 2(pbnHH)]2+ species from [Ru(bpy)2(pbn)] 2+ were studied in an aqueous medium. Formation of the one-electron-reduced species as a result of reduction by a solvated electron (k = 3.0 × 1010 M-1 s-1) or CO 2•- (k = 4.6 × 109 M-1 s-1) or reductive quenching of an MLCT excited state by 1,4-diazabicyclo[2.2.2]octane (k = 1.1 × 109 M-1 s-1) is followed by protonation of the reduced species (pK a = 11). Dimerization (k7a = 2.2 × 108 M-1 s-1) of the singly reduced protonated species, [Ru(bpy)2(pbnH)]2+, followed by disproportionation of the dimer as well as the cross reaction between the singly reduced protonated and nonprotonated species (k8 = 1.2 × 108 M-1 s-1) results in the formation of the final [Ru(bpy)2(pbnHH)]2+ product together with an equal amount of the starting complex, [Ru(bpy)2(pbn)]2+. At 0.2°C, a dimeric intermediate, most likely a π-stacking dimer, was observed that decomposes thermally to form an equimolar mixture of [Ru(bpy) 2(pbnHH)]2+ and [Ru(bpy)2(pbn)]2+ (pH < 9). The absence of a significant kinetic isotope effect in the disproportionation reaction of [Ru(bpy)2(pbnH)] 2+ and its conjugate base (pH > 9) indicates that disproportionation occurs by a stepwise pathway of electron transfer followed by proton transfer.

Original languageEnglish
Pages (from-to)3958-3968
Number of pages11
JournalInorganic Chemistry
Volume47
Issue number10
DOIs
Publication statusPublished - May 19 2008

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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