On the Effect of Electron Relay Redox Potential on Electron Transfer Reactions in a Water Photoreduction Model System

Amouyal, Edmond; Zidler, Bertrand

doi:10.1002/ijch.198200023

Cited by 63 publications

(16 citation statements)

References 32 publications

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“…The emission spectral data in Figure shows that, at both low and high loading levels, the quenching follows the order MV 2+ > 2DQ 2+ > 3DQ 2+ > 4DQ 2+ . The electron transfer quenching of Ru(bpy) 3 2+ * by several bipyridinium ions in solution has been examined, and the quenching rate constants are found to increase as the bipyridinium reduction potentials become less negative. , For the diquat ( n DQ 2+ ) series reported here, the order of quenching is as is expected from the reduction potentials, indicating that as the driving force for the forward electron transfer decreases, the propensity to quench the intrazeolitic Ru(bpy) 3 2+ * by electron transfer also decreases. The reduction potential of methyl viologen is between that of 2DQ 2+ and 3DQ 2+ , yet it quenches Ru(bpy) 3 2+ * most efficiently.…”

Section: Discussionmentioning

confidence: 54%

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Intrazeolitic Photochemical Charge Separation for Ru(bpy)₃²⁺−Bipyridinium System: Role of the Zeolite Structure

et al. 1999

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The pore structure of zeolite Y consists of 13 Å supercages connected through 7 Å windows. This study deals with the intrazeolitic photoelectron transfer from trisbipyridyl ruthenium (II) (Ru(bpy) 3 2+ ) synthesized within zeolite Y supercages to ion-exchanged bipyridinium molecules in neighboring supercages. Three N,N′-dialkyl-2,2′-bipyridinium ions and a 4,4′-bipyridinium ion with reduction potentials varying from -0.37 to -0.65 V have been studied. For the 2,2′-bipyridinium salts (members of the diquat family), two, three, and four CH 2 bridging units abbreviated as 2DQ 2+ , 3DQ 2+ , and 4DQ 2+ , respectively, have been examined. The fourth viologen is 1,1′-dimethyl-4,4′-bipyridinium, commonly known as methyl viologen and abbreviated here as MV 2+ . Because of the limitations of the time-resolved diffuse reflectance instrument, only a lower limit of the forward electron transfer rate constant from Ru(bpy) 3 2+ * to the bipyridinium ion was obtained and is >10 7 s -1 . The back electron transfer from the photogenerated bipyridinium radical ions to Ru(bpy) 3 3+ was monitored at different intrazeolitic bipyridinium concentrations. At low loadings of bipyridinium ions (1 per 10-15 supercages), the transient signal between 360 and 390 nm has contributions from both Ru(bpy) 3 2+ * and the bipyridinium radical ions, since the bipyridinium ion concentration was not high enough to quench all of the Ru(bpy) 3 2+ *. The decay of this signal (360-390 nm) could be fitted to the sum of two exponentials, representing the disappearance of unquenched Ru(bpy) 3 2+ * and the back electron transfer from the bipyridinium radical ions to Ru(bpy) 3 3+ . The rate constants for the back electron transfer for 2DQ 2+ , MV 2+ , 3DQ 2+ , and 4DQ 2+ were found to be 4.0 × 10 4 , 1.7 × 10 4 , 1.1 × 10 4 , and 7.3 × 10 3 s -1 . The decrease in the electron transfer rates with increasing driving force for the reaction indicates that the electron transfer is occurring in the Marcus inverted region. At high loadings of the bipyridinium ions (1.2-1.7 molecules/supercage), the bipyridinium radical ions were considerably longer lived, and a simple exponential decay no longer described the loss of the bipyridinium radical signal. A model that allows for electron exchange processes between bipyridinium ions to compete with the back electron transfer was necessary. This kinetic model allowed us to extract the back electron transfer rate at high loadings along with the rate constants for electron hopping and a second-order electron (bipyridinium radical)/hole (Ru(bpy) 3 3+ ) recombination process. For the series 2DQ 2+ , MV 2+ , 3DQ 2+ , and 4DQ 2+ with high loading, the back electron transfer rate constants were 2.5 × 10 5 , 9 × 10 4 , 1.8 × 10 5 , and 1.2 × 10 5 s -1 , higher than the low loading samples. In the high loading case, longer lived charge separation was observed because of the presence of a route for charge propagation by electron hopping via the densely packed viologen molecules.Practical solar energy conversion processes, such as the p...

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Section: Discussionmentioning

confidence: 54%

“… a Volts vs NHE (ref ). b The value E ° (Ru 3+ /Ru 2+ ) = 1.26 V (vs NHE) was used in this calculation. …”

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confidence: 99%

Intrazeolitic Photochemical Charge Separation for Ru(bpy)₃²⁺−Bipyridinium System: Role of the Zeolite Structure

et al. 1999

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“…The choice of an electron relay is generally crucial to the success of a system; a good relay oxidatively quenches the excited photosensitizer, thereby creating charge separation at the cost of reducing the systems free energy. Numerous relays have been used in place of methyl viologen, including a variety of quaternary bipyridines [24,25] as well as several cobalt [26][27][28] and rhodium [8,[29][30][31] complexes. Other alternatives include bridged systems where a photosensitizer is covalently linked to a hydrogen evolving metal complex.…”

Section: -A C H T U N G T R E N N U N G (N^n)]mentioning

confidence: 99%

Visible Light Induced Catalytic Water Reduction without an Electron Relay

Tinker

McDaniel

Curtin

et al. 2007

Chemistry A European J

211

238

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Protons from water are reduced by a catalytic system composed of a heteroleptic iridium(III) photosensitizer [Ir(ppy)2(bpy)]+, platinum catalyst, and sacrificial reductant. The hydrogen quantum yield reaches 0.26 in this study, which proceeds via reductive quenching of the excited photosensitizer by triethanolamine. This simplified approach allows the characterization of degradation products that are otherwise obscured in more complex systems. A novel 16-well setup for parallel kinetic analysis of H2 evolution enables high-throughput screening of reaction conditions and quantization of the decaying reaction rate. DFT calculations rationalize the differences between this and previous studies on tris-diimine ruthenium(II) photosensitizers.

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“…between similarly charged species, was also reported. [28][29][30] The hopping mechanism of this transfer may not be excluded since the length of the diffusion step is not negligible even for heavy particles, especially in overcooled water. 31 For proton transfer the hopping mechanism is particularly favorable at any since the tunneling parameter L is a hundred times smaller.…”

Section: ͑12͒mentioning

confidence: 99%

Hopping reactions of charged particles

Burshteǐn

Fedorenko

1997

The Journal of Chemical Physics

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Articles you may be interested inEffect of an external electric field on the diffusion-influenced geminate reversible reaction of a neutral particle and a charged particle in three dimensions. IV. Excited-state ABCD reaction J. Chem. Phys. 140, 064502 (2014); 10.1063/1.4864202Effect of an external electric field on the diffusion-influenced geminate reversible reaction of a neutral particle and a charged particle in three dimensions. III. Ground-state ABCD reaction Direct ab initio dynamics calculations for rates and the kinetic isotope effects of multiproton transfer in ClONO 2 + HCl → HNO 3 + Cl 2 reactions with water clusters: Breakdown of the rule of the geometric mean Diffusion-influenced reactions of particles with several active sites J. Chem. Phys. 128, 155105 (2008); 10.1063/1.2898091 Long-time behavior of the diffusion-controlled A+B→0 reaction with hopping energy relaxationThe hopping theory of transfer reactions is essentially generalized to account for the electrostatic interaction between reactants. An application is made for a solvated electron that may be trapped by ions in the course of a random walk in liquid solutions. The hopping reaction constant differs essentially from the diffusional constant but exhibits a similar dependence on the Onsager radius: reactions with anions are strongly suppressed while reactions with cations are significantly accelerated.

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On the Effect of Electron Relay Redox Potential on Electron Transfer Reactions in a Water Photoreduction Model System

Cited by 63 publications

References 32 publications

Intrazeolitic Photochemical Charge Separation for Ru(bpy)₃²⁺−Bipyridinium System: Role of the Zeolite Structure

Intrazeolitic Photochemical Charge Separation for Ru(bpy)₃²⁺−Bipyridinium System: Role of the Zeolite Structure

Visible Light Induced Catalytic Water Reduction without an Electron Relay

Hopping reactions of charged particles

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On the Effect of Electron Relay Redox Potential on Electron Transfer Reactions in a Water Photoreduction Model System

Cited by 63 publications

References 32 publications

Intrazeolitic Photochemical Charge Separation for Ru(bpy)32+−Bipyridinium System: Role of the Zeolite Structure

Intrazeolitic Photochemical Charge Separation for Ru(bpy)32+−Bipyridinium System: Role of the Zeolite Structure

Visible Light Induced Catalytic Water Reduction without an Electron Relay

Hopping reactions of charged particles

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Product

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Intrazeolitic Photochemical Charge Separation for Ru(bpy)₃²⁺−Bipyridinium System: Role of the Zeolite Structure

Intrazeolitic Photochemical Charge Separation for Ru(bpy)₃²⁺−Bipyridinium System: Role of the Zeolite Structure