Photochemical and Radiolytic Production of an Organic Hydride Donor with a Ru<sup>II</sup> Complex Containing an NAD<sup>+</sup> Model Ligand

Polyansky, Dmitry E.; Cabelli, Diane E.; Muckerman, James T.; Fujita, Etsuko; Koizumi, Tadayoshi; Fukushima, Takashi; Wada, Tohru; Tanaka, Koji

doi:10.1002/anie.200700304

Cited by 91 publications

(88 citation statements)

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“…The homobimetallic complexes [(phen) 2 Ru(BL)Ru(phen) 2 ](PF 6 ) 4 collect up to two or four electrons on the BL (π*) orbitals (phen = 1,10-phenanthroline; BL = 9,11,20,22-tetraazatetrapyrido[3,2-a:2′3′-c:3′′,2′′-1:2′′′,3′′′-n]pentacene (tatpp) or 9,11,20,22-tetraazatetrapyrido[3,2-a:2′3′-c:3′′,2′′-1:2′′′,3′′′-n]pentacene-10,21-quinone (tatpq)) [7,8]. The Ru monometallic [(bpy) 2 Ru(pbn)](PF 6 ) 2 undergoes proton-coupled two-electron reduction of the NAD/NADH + model ligand to produce [(bpy) 2 Ru(pbnHH)] 2+ (pbn = 2-(2-pyridyl)benzo[ b ]-1,5-naphthyridine, NAD = nicotinamide adenine dinucleotide) [9,10]. These early systems display ligand-centered photoinitiated electron collection, but do not perform photocatalytic reduction of H 2 O to H 2 .…”

Section: Introductionmentioning

confidence: 99%

A Series of Supramolecular Complexes for Solar Energy Conversion via Water Reduction to Produce Hydrogen: An Excited State Kinetic Analysis of Ru(II),Rh(III),Ru(II) Photoinitiated Electron Collectors

et al. 2011

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Mixed-metal supramolecular complexes have been designed that photochemically absorb solar light, undergo photoinitiated electron collection and reduce water to produce hydrogen fuel using low energy visible light. This manuscript describes these systems with an analysis of the photophysics of a series of six supramolecular complexes, [{(TL)2Ru(dpp)}2RhX2](PF6)5 with TL = bpy, phen or Ph2phen with X = Cl or Br. The process of light conversion to a fuel requires a system to perform a number of complicated steps including the absorption of light, the generation of charge separation on a molecular level, the reduction by one and then two electrons and the interaction with the water substrate to produce hydrogen. The manuscript explores the rate of intramolecular electron transfer, rate of quenching of the supramolecules by the DMA electron donor, rate of reduction of the complex by DMA from the 3MLCT excited state, as well as overall rate of reduction of the complex via visible light excitation. Probing a series of complexes in detail exploring the variation of rates of important reactions as a function of sub-unit modification provides insight into the role of each process in the overall efficiency of water reduction to produce hydrogen. The kinetic analysis shows that the complexes display different rates of excited state reactions that vary with TL and halide. The role of the MLCT excited state is elucidated by this kinetic study which shows that the 3MLCT state and not the 3MMCT is likely that key contributor to the photoreduction of these complexes. The kinetic analysis of the excited state dynamics and reactions of the complexes are important as this class of supramolecules behaves as photoinitiated electron collectors and photocatalysts for the reduction of water to hydrogen.

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Section: Introductionmentioning

confidence: 99%

A Series of Supramolecular Complexes for Solar Energy Conversion via Water Reduction to Produce Hydrogen: An Excited State Kinetic Analysis of Ru(II),Rh(III),Ru(II) Photoinitiated Electron Collectors

et al. 2011

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“…[26] The reduced species is a pbn radical anion. When using continuous excitation (λ > 300 nm), the [Ru(bpy) 2 3 CN/ H 2 O, thereby making unambiguous assignment of the spectral features observed in the course of the photochemical conversion possible.…”

Section: A Few Specific Case Studies Of Photoinduced Charge Accumulationmentioning

confidence: 99%

Photoinduced Charge Accumulation in Molecular Systems

Bonn

Wenger²

2015

Chimia

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Fuel-forming reactions such as CO 2 reduction or water splitting require multiple redox equivalents. When aiming at light-driven production of energy-rich chemicals, nowadays often referred to as solar fuels, it therefore becomes important to master the photoinduced accumulation of electrons or holes on individual molecular components. Featured in this short review are some of the key molecular systems explored in this emerging field of research. This includes for example a trinuclear Ru(ii)-Rh(iii)-Ru(iii) complex or an Ir(iii)-sensitized polyoxotungstate hybrid, but also several systems in which electron or hole collection occurs at organic moieties such as perylenebis(dicarboximide), quinone-containing or oligotriarylamine-based units. In many cases the photodriven accumulation of charge requires the use of sacrificial electron donors, but there exist also a handful of studies in which redox equivalents can be accumulated without the use of such additives.

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“…63 The largest hfc value (3.95 G) is significantly smaller than the value without Mg 2 þ ion (4.60 G) due to the spin delocalization to the Mg nucleus. 13,40,64,68 Such onestep versus multistep pathways have been discussed extensively in hydride transfer reactions of dihydronicotinamide coenzyme (NADH) and analogues, particularly including the effect of metal cations and acids, [69][70][71][72][73][74][75][76][77][78][79] because of the essential role of acid catalysis in the enzymatic reduction of carbonyl compounds by NADH. À bound to both Mg 2 þ and the amide proton without detection of an intermediate without hydrogen bonding.…”

Section: Scheme 29mentioning

confidence: 99%

Proton‐Coupled Electron Transfer in Hydrogen and Hydride Transfer Reactions

Fukuzumi

2010

Physical Inorganic Chemistry

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ET. [7][8][9]12,13 The inner-sphere character in organic ET reactions is established by their high sensitivity to steric effects. 14 As the H DA value increases further, the ET process is coupled with the subsequent PT process. This is generally referred to as proton-coupled electron transfer (PCET). [15][16][17][18][19][20][21][22][23][24] What distinguishes PCET from classic HAT is that the proton and electron are transferred between two different (noninteracting) orbitals. In particular, PCET plays an important role in enzymatic reactions such as those of lipoxygenases, which are mononuclear nonheme iron enzymes. [25][26][27] The key step of the lipoxygenase reactions is PCET from a substrate to ferric hydroxide cofactor (Fe(III)-OH) to produce Fe(II)-OH 2 and a radical intermediate substrate, when an electron goes to the metal center and a proton is transferred to the OH ligand. 28,29 When PCET is a concerted process whereby a proton and an electron are transferred simultaneously, such a PCET process may be merged into the one-step HAT process. 30 Thus, there has been long-standing ambiguity as to the mechanistic borderline where a sequential PCET pathway is changed to a one-step HAT pathway or vice versa. Understanding HAT reactions certainly requires knowledge of the thermodynamics and kinetics of the overall HAT, ET, and PT steps.Considering only the two-electron reduction of A, the reduction and protonation give nine species at different oxidation and protonation states as shown in Scheme 2.3. Each species can have an interaction with a variety of metal ions (M n þ ), and such an interaction can control each ET and protonation step, as well as their combined step (hydrogen transfer) in Scheme 2.3. [31][32][33][34][35] The binding of M n þ to radical anions of electron acceptors results in a substantial increase in the ET rate. 31-35 This is defined herein as metal ion-coupled electron transfer (MCET) in analogy to PCET. 36 The binding of M n þ with A . À can also be combined with other noncovalent interactions such as hydrogen bonding and p-p interaction. 36 The initial PCET and MCET processes are followed by the second PCET and MCET processes to afford AH 2 as the two-electron reduced species of A with two protons. 36 SCHEME 2.3 MECHANISTIC BORDERLINE BETWEEN ONE-STEP HAT AND SEQUENTIAL PCETAmong a variety of hydrogen donors, dihydronicotinamide adenine dinucleotide (NADH) and analogues have attracted particular interest, because NADH is the most important source of hydrogen and hydride ion in biological redox reactions. 37-40 If HAT from NADH and analogues to hydrogen atom acceptors (A) occurs in a one-step manner, NAD . and AH . would be the only detectable radical products. In the case of sequential electron and proton transfer, however, NADH . þ and A . À would also be detected as the intermediates for the hydrogen transfer reaction. The radical intermediates such as NADH . þ , NAD . , and the corresponding analogues are involved in a variety of thermal and photoinduced ET reactions of NADH and analo...

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Photochemical and Radiolytic Production of an Organic Hydride Donor with a Ru^II Complex Containing an NAD⁺ Model Ligand

Cited by 91 publications

References 30 publications

A Series of Supramolecular Complexes for Solar Energy Conversion via Water Reduction to Produce Hydrogen: An Excited State Kinetic Analysis of Ru(II),Rh(III),Ru(II) Photoinitiated Electron Collectors

A Series of Supramolecular Complexes for Solar Energy Conversion via Water Reduction to Produce Hydrogen: An Excited State Kinetic Analysis of Ru(II),Rh(III),Ru(II) Photoinitiated Electron Collectors

Photoinduced Charge Accumulation in Molecular Systems

Proton‐Coupled Electron Transfer in Hydrogen and Hydride Transfer Reactions

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Photochemical and Radiolytic Production of an Organic Hydride Donor with a RuII Complex Containing an NAD+ Model Ligand

Cited by 91 publications

References 30 publications

A Series of Supramolecular Complexes for Solar Energy Conversion via Water Reduction to Produce Hydrogen: An Excited State Kinetic Analysis of Ru(II),Rh(III),Ru(II) Photoinitiated Electron Collectors

A Series of Supramolecular Complexes for Solar Energy Conversion via Water Reduction to Produce Hydrogen: An Excited State Kinetic Analysis of Ru(II),Rh(III),Ru(II) Photoinitiated Electron Collectors

Photoinduced Charge Accumulation in Molecular Systems

Proton‐Coupled Electron Transfer in Hydrogen and Hydride Transfer Reactions

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Photochemical and Radiolytic Production of an Organic Hydride Donor with a Ru^II Complex Containing an NAD⁺ Model Ligand