Ru Complexes That Can Catalytically Oxidize Water to Molecular Dioxygen

Romero, Isabel; Rodríguez, Montserrat; Sens, Cristina; Mola, Joaquim; Kollipara, Mohan Rao; Francàs, Laia; Mas‐Marzá, Elena; Escriche, Lluís; Llobet, Antoni

doi:10.1021/ic700911y

Cited by 142 publications

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“…Formation. Accumulated experimental and theoretical studies (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29) on artificial photosynthesis systems have elucidated dual possible mechanisms of the water splitting reaction: (i) the radical coupling (RC) mechanism and (ii) the acid-base mechanism. Tanaka and coworkers have proposed the former mechanism for the water splitting reaction by their Ru-quinone complexes as illustrated in Fig.…”

Section: Possible Electronic and Spin States Of Mononuclear And Binucmentioning

confidence: 99%

“…In the past decades, a number of experimental and theoretical studies (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29) have been performed to design artificial photosynthetic systems that mimic native PSII systems. Many binuclear transition-metal catalysts such as LðH 2 OÞM-O-MðOH 2 ÞL or LðH 2 OÞM-BL-MðOH 2 Þ (where L and BL are nonbridging and bridging organic ligands, respectively) were prepared and characterized for their catalytic properties toward water oxidation (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21).…”

mentioning

confidence: 99%

“…Many binuclear transition-metal catalysts such as LðH 2 OÞM-O-MðOH 2 ÞL or LðH 2 OÞM-BL-MðOH 2 Þ (where L and BL are nonbridging and bridging organic ligands, respectively) were prepared and characterized for their catalytic properties toward water oxidation (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). By combining structural and kinetic studies, impressive progress has been achieved in unraveling the molecular mechanism of the catalytic action of the so-called blue dimmer (12), ½cis; cis-ðbpyÞ 2 ðH 2 OÞRu-O-RuðOH 2 ÞðbpyÞ 2 ðbpy ¼ 2; 2 0 -bipyridineÞ; however, the detailed mechanism of the final stage of the O─O bond formation and O 2 evolution remains unsettled despite several theoretical investigations (22-24, 26, 28).…”

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confidence: 99%

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Similarities of artificial photosystems by ruthenium oxo complexes and native water splitting systems

Tanaka

Isobe

Yamanaka

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The nature of chemical bonds of ruthenium(Ru)-quinine(Q) complexes, mononuclear ½RuðtrpyÞð3,5-t-Bu 2 QÞðOH 2 Þ ðClO 4 Þ 2 (trpy ¼ 2,2 0 : 6 0 ,2 0 0 -terpyridine, 3,5-di-tert-butyl-1,2-benzoquinone) (1), and binuclear ½Ru 2 ðbtpyanÞð3,6-di-Bu 2 QÞ 2 ðOH 2 Þ 2þ ðbtpyan ¼ 1,8-bisð2,2 0 : 6 0 ,2 0 0 -terpyrid-4 0 -ylÞanthracene, 3,6-t-Bu 2 Q ¼ 3,6-di-tertbutyl-1,2-benzoquinone) (2), has been investigated by broken-symmetry (BS) hybrid density functional (DFT) methods. BS DFT computations for the Ru complexes have elucidated that the closed-shell structure (2b) Ru(II)-Q complex is less stable than the open-shell structure (2bb) consisting of Ru(III) and semiquinone (SQ) radical fragments. These computations have also elucidated eight different electronic and spin structures of tetraradical intermediates that may be generated in the course of water splitting reaction. The Heisenberg spin Hamiltonian model for these species has been derived to elucidate six different effective exchange interactions (J) for four spin systems. Six J values have been determined using total energies of the eight (or seven) BS solutions for different spin configurations. The natural orbital analyses of these BS DFTsolutions have also been performed in order to obtain natural orbitals and their occupation numbers, which are useful for the lucid understanding of the nature of chemical bonds of the Ru complexes. Implications of the computational results are discussed in relation to the proposed reaction mechanisms of water splitting reaction in artificial photosynthesis systems and the similarity between artificial and native water splitting systems.four redox center | manganese clusters | water oxidation | oxyl radical | O-O bond formation P hotosynthesis is one of the most important chemical processes on our planet. Extensive experimental studies (1-6) on the process have revealed that oxygenic photosynthesis involves several protein-cofactor complexes embedded in the photosynthetic thylakoid membranes of plants, green algae, and cyanobacteria. Among these complexes, photosystem II (PSII) has a prominent role because it catalyzes the oxidation of water (, which is the prerequisite for all aerobic life. The main cyclic process to catalyze the water-oxidation consists of successive four steps, which is referred to as the Kok cycle (6). During this process, the oxygen-evolving complex (OEC), the catalyst of the water oxidation reaction, takes five oxidation states (S 0 -S 4 ). The OEC in PSII contains an inorganic cluster consisting of four manganese ions and one calcium ion that are bridged by at least five oxygens; the active site is therefore expressed with the CaMn 4 O 5 cluster (3) (5). Very recently, the electronic structure and reactivity of 3 (7-10) have been elucidated based on the new high-resolution X-ray structure (5).In the past decades, a number of experimental and theoretical studies (11-29) have been performed to design artificial photosynthetic systems that mimic native PSII systems. Many binuclear transition-metal catalysts s...

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Section: Possible Electronic and Spin States Of Mononuclear And Binucmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Similarities of artificial photosystems by ruthenium oxo complexes and native water splitting systems

Tanaka

Isobe

Yamanaka

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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“…Complementing the work on Mn has been the earlier discovery that ruthenium-based catalysts, such as the "blue dimer," that can photooxidize water to dioxygen (Gersten et al 1982;Liu et al 2008;Romero et al 2008), and the recent spectacular work of Duan et al (2012), which has reported a rationally designed Rubased catalyst with an unprecedented turnover rate of 300 per sec, comparable to that of PSII. But perhaps the most practical catalysts for water splitting are based on Co, a relatively abundant element.…”

Section: Artificial Photosynthesismentioning

confidence: 99%

Photosystem II: The Water-Splitting Enzyme of Photosynthesis

Barber

2012

Cold Spring Harbor Symposia on Quantitative Biology

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The oxygen in our atmosphere is derived and maintained by the water-splitting process of photosynthesis. The enzyme that facilitates this reaction and therefore underpins virtually all life on our planet is known as photosystem II (PSII), a multisubunit enzyme embedded in the lipid environment of the thylakoid membranes of plants, algae, and cyanobacteria. During the past 10 years, crystal structures of a 700-kDa cyanobacterial dimeric PSII complex have been reported with ever-increasing improvement in resolution-the latest at 1.9 Å . Thus, the organizational and structural details of its many subunits and cofactors are now well understood. The water-splitting site was revealed as a cluster of four Mn ions and one Ca ion surrounded by aminoacid side chains, of which seven provide ligands to the metals. The metal cluster is organized as a cubane-like structure composed of three Mn ions and the one Ca 2þ ion linked by oxo bonds. The fourth Mn is attached to the cubane via one of its bridging oxygens together with another oxo bridge to an Mn ion of the cubane. The overall structure of the catalytic site provides a framework to propose a mechanistic scheme for the water-splitting process and gives a blueprint for the development of catalysts that mimick the reaction in an artificial chemical system as a means to generate solar fuels.

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“…Among several metal cations, ruthenium ion is widely used in many applications including catalyst 1,2 , dyesensitized solar cell [3][4][5] , and in medicine as an anticancer agent [6][7][8] . However, extensive use of ruthenium ion could lead to accumulation of wastes harmful to the environment, as ruthenium ion exhibits various forms of toxicity 9 .…”

Section: Introductionmentioning

confidence: 99%