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 language | English |
|---|---|
| Pages (from-to) | 3958-3968 |
| Number of pages | 11 |
| Journal | Inorganic Chemistry |
| Volume | 47 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - May 19 2008 |
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- Inorganic Chemistry
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Mechanism of hydride donor generation using a Ru(II) complex containing an NAD+ model ligand : Pulse and steady-state radiolysis studies. / Polyansky, Dmitry; Cabelli, Diane; Muckerman, James; Fukushima, Takashi; Tanaka, Koji; Fujita, Etsuko.
In: Inorganic Chemistry, Vol. 47, No. 10, 19.05.2008, p. 3958-3968.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Mechanism of hydride donor generation using a Ru(II) complex containing an NAD+ model ligand
T2 - Pulse and steady-state radiolysis studies
AU - Polyansky, Dmitry
AU - Cabelli, Diane
AU - Muckerman, James
AU - Fukushima, Takashi
AU - Tanaka, Koji
AU - Fujita, Etsuko
PY - 2008/5/19
Y1 - 2008/5/19
N2 - 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.
AB - 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.
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U2 - 10.1021/ic702139n
DO - 10.1021/ic702139n
M3 - Article
VL - 47
SP - 3958
EP - 3968
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 10
ER -