Photoinduced energy and electron transfer processes in heteropolynuclear polypyridyl complexes of Ru(<scp>ii</scp>) and Fe(<scp>ii</scp>)

Lafolet, Frédéric; Chauvin, Jérôme; Collomb, Marie‐Noëlle; Deronzier, Alain; Laguitton-Pasquier, Hélène; Leprêtre, Jean‐Claude; Vial, Jean-Claude; Brasme, Bernard

doi:10.1039/b303156j

Cited by 23 publications

(26 citation statements)

References 35 publications

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“…As previously observed for the [Ru(LL n )Fe] 4+ complexes, [14] the E 1/2 values of the Fe II /Fe III and Ru II /Ru III redox systems decrease slightly upon increasing the number of methylenes in the aliphatic bridge (Table 2). This E 1/2 variation is due to a slightly higher electron-donor effect of the LL 6 ligand compared to LL 4 , and of the latter to LL 2 .…”

Section: Electrochemistrysupporting

confidence: 72%

“…[24] This effect is weak for [{Ru(LL 2 )} 3 Fe] 8+ {τ = 1.07 μs compared to 1.11 μs for [Ru(LL 2 )] 2+ } and larger for complexes having a longer aliphatic bridge such as n = 4 and n = 6 (Table 4). Although this phenomenon involves the proximity of cationic species, and therefore electrostatic repulsion, such an EET mechanism has already been suspected for other systems containing a [Ru(bpy) 3 ] 2+ *-like donor with cationic iron [14,15] or manganese [12,25] complexes as acceptor. Nevertheless, the luminescence quantum yield of the [{Ru-(LL n )} 3 can only be due to a higher probability of a dynamic quenching between Fe and Ru by folding up of the molecule in the tetranuclear structures than in the binuclear ones.…”

Section: Energy Transfermentioning

confidence: 92%

“…[14] Moreover, only the first reduction wave is clearly seen. A strong adsorption phenomenon coupled to the second reduction process leads to an important distortion of the third one.…”

Section: Electrochemistrymentioning

confidence: 95%

“…It has been established previously [14,26,27] (5) and (6) 8+ complexes by EET is incomplete and the luminescence lifetime of the Ru II * excited state is sufficiently long-lived (1 μs) to allow a bimolecular reaction using an external electron acceptor. In addition, the lifetime of the excited state of the Fe II moiety is too short (Ͻ1 ns) to undergo an efficient bimolecular electron transfer with ArN 2 + .…”

Section: Photoinduced Electron Transfermentioning

confidence: 98%

“…Thus, a pure electronic energy transfer (EET) can be considered as the main quenching process. [14,19] The quenching rate constant (k q ) was determined from Equation (3) …”

Section: Energy Transfermentioning

confidence: 99%

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Tetranuclear Polypyridyl Complexes of Ru^II and Fe^II: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

et al. 2005

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Three heterotetranuclear complexes [{RuII(bpy)2(LLn)}3FeII]8+ {bpy = 2,2'‐bipyridine, n = 2, 4, 6; denoted [{Ru(LLn)}3Fe]8+}, in which one iron centre is complexed by three RuII‐tris‐bipyridine‐like moieties containing covalently bridging bis‐bipyridine LLn ligands, have been synthesised and characterised. The stability and the electrochemical, photophysical and photochemical properties of these complexes have been investigated in CH3CN. The cyclic voltammograms of all complexes exhibit two successive reversible oxidation processes in the positive region, corresponding to the FeII/FeIII and RuII/RuIII redox couples. These systems are clearly separated (ΔE1/2 about 300 mV), which indicates the absence of an electronic connection between the two subunits. In the negative region, three successive reversible four‐electron systems are observed, corresponding to the ligand‐based reduction processes. The two oxidized forms of the complexes [{RuII(LLn)}3FeIII]9+ and [{RuIII(LLn)}3FeIII]12+, which are obtained by two successive exhaustive electrolyses, are very stable. The [{Ru(LLn)}3Fe]8+ complexes are luminescent, which shows that the covalent linkage between the RuII‐tris‐bipyridine and FeII‐tris‐bipyridine subunits leads to an only partial quenching of the RuII* excited states by energy transfer to the FeII centre. The luminescence lifetime and quantum yield are found to be independent of the complexes’ concentration, thus indicating that the energy‐transfer process is only due to an intramolecular electron‐exchange mechanism. Quantitative photoinduced oxidation of the tetranuclear complexes has been performed by continuous photolysis experiments in the presence of a large excess of a diazonium salt, which plays the role of a sacrificial oxidant. Two successive oxidation processes (FeII → FeIII and RuII → RuIII) are observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Section: Electrochemistrysupporting

confidence: 72%

Section: Energy Transfermentioning

confidence: 92%

“…[14] Moreover, only the first reduction wave is clearly seen. A strong adsorption phenomenon coupled to the second reduction process leads to an important distortion of the third one.…”

Section: Electrochemistrymentioning

confidence: 95%

Section: Photoinduced Electron Transfermentioning

confidence: 98%

“…Thus, a pure electronic energy transfer (EET) can be considered as the main quenching process. [14,19] The quenching rate constant (k q ) was determined from Equation (3) …”

Section: Energy Transfermentioning

confidence: 99%

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Tetranuclear Polypyridyl Complexes of Ru^II and Fe^II: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

et al. 2005

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An Efficient Ru^II–Rh^III–Ru^II Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

et al. 2014

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The development of multicomponent molecular systems for the photocatalytic reduction of water to hydrogen has experienced considerable growth since the end of the 1970s. Recently, with the aim of improving the efficiency of the catalysis, single-component photocatalysts have been developed in which the photosensitizer is chemically coupled to the hydrogen-evolving catalyst in the same molecule through a bridging ligand. Until now, none of these photocatalysts has operated efficiently in pure aqueous solution: a highly desirable medium for energy-conversion applications. Herein, we introduce a new ruthenium-rhodium polypyridyl complex as the first efficient homogeneous photocatalyst for H 2 production in water with turnover numbers of several hundred. This study also demonstrates unambiguously that the catalytic performance of such systems linked through a nonconjugated bridge is significantly improved as compared to that of a mixture of the separate components.Solar-light-induced water splitting into hydrogen and oxygen, also referred as artificial photosynthesis, is a very attractive sustainable approach to produce the fuel H 2 as a clean and renewable energy carrier for the future. [1,2] Since the end of the 1970s, considerable effort has been devoted to the development of multicomponent homogeneous molecular systems for photocatalytic H 2 evolution that consist of a light-harvesting antenna (photosensitizer, PS), a hydrogen-evolving catalyst (HEC), and a sacrificial electron donor coupled or not to an electron mediator. [3][4][5][6][7][8] However, systems operating in pure aqueous solution-a highly desirable medium for their subsequent application in photoelectrochemical watersplitting devices [9][10][11][12][13] -remain only moderately developed. Among them, efficient molecular systems with a turnover number versus catalyst (denoted TON) above 100 have been obtained with catalysts based on rhodium, [14][15][16][17] platinum, [18] and cobalt complexes. [12,[19][20][21][22][23] In some cases, TONs of 1000 or more have been reached, generally by using a low concentration of the catalyst in combination with a high PS/HEC ratio. [17,[19][20][21]23] Besides the development of such multicomponent systems, more recently, various single-component photocatalysts have been designed by coupling the PS and the HEC in the same molecule through a bridging ligand. These molecular photocatalysts, which operate in the presence of an electron donor, combine a Ru, Ir, Re, or Os complex, a porphyrin (Zn, Mg, or Al), or an organic dye as the PS with a Pt, Pd, Rh, Co, or Fe complex as the HEC. [3][4][5][6][7][8][24][25][26][27][28] However, if the objective is to improve the efficiency of the catalysis by facilitating the intramolecular electron transfer from the PS to the catalyst, the real benefit of such linked systems is often difficult to estimate. Indeed, for linked systems connected through a labile ligand, dissociation can occur, and when a conjugated link is used, it can alter the electronic properties of each component, t...

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An Efficient Ru^II–Rh^III–Ru^II Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

et al. 2014

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Photoinduced energy and electron transfer processes in heteropolynuclear polypyridyl complexes of Ru(ii) and Fe(ii)

Cited by 23 publications

References 35 publications

Tetranuclear Polypyridyl Complexes of Ru^II and Fe^II: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

Tetranuclear Polypyridyl Complexes of Ru^II and Fe^II: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

An Efficient Ru^II–Rh^III–Ru^II Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

An Efficient Ru^II–Rh^III–Ru^II Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

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Photoinduced energy and electron transfer processes in heteropolynuclear polypyridyl complexes of Ru(ii) and Fe(ii)

Cited by 23 publications

References 35 publications

Tetranuclear Polypyridyl Complexes of RuII and FeII: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

Tetranuclear Polypyridyl Complexes of RuII and FeII: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

An Efficient RuII–RhIII–RuII Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

An Efficient RuII–RhIII–RuII Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

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Tetranuclear Polypyridyl Complexes of Ru^II and Fe^II: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

Tetranuclear Polypyridyl Complexes of Ru^II and Fe^II: Synthesis, Electrochemical, Photophysical and Photochemical Behaviour

An Efficient Ru^II–Rh^III–Ru^II Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution

An Efficient Ru^II–Rh^III–Ru^II Polypyridyl Photocatalyst for Visible‐Light‐Driven Hydrogen Production in Aqueous Solution