Redox-active ligands in artificial photosynthesis: a review

Benkó, Tímea; Lukács, Dávid; Li, Mingtao; Pap, József S.

doi:10.1007/s10311-022-01448-3

Cited by 8 publications

(14 citation statements)

References 188 publications

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“…[7] Also, bidentate NILs based on hetero-1,3diene systems like catecholates, [8] thiolenes, [9] or diimines [10] were investigated thoroughly, which has led to a good number of applications in small molecule activation, [11] catalysis, [12] or metal-organic frameworks, [13] as well as to fundamental progress in artificial photosynthesis. [14] Tridentate redox-active ligands belong to the class of pincer ligands and show strong binding affinities to metal ions due to the chelate effect. This often leads to highly stable molecular complexes with finely tunable redox properties making them superior in modern ligand design to low coordinating NILs.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Bis(pyridylimino)isoindolide Alkali Metal Complexes in Three Redox States

2023

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Non‐innocent ligands (NILs) like bis(pyridylimino)isoindolide (BPI) play crucial roles in coordination chemistry, biosciences, catalysis and material sciences. Investigating the isolated redox states of NILs is inevitable for understanding their redox‐activity and fine‐tuning the properties of corresponding metal complexes. The limited number of fundamental studies on the coordination behavior and redox chemistry of reduced BPI species is suggested to hamper further applications of the title compounds. This work describes for the first time the isolation of alkali metal complexes of BPI and Me2BPI in three different oxidation states and their characterization by means of NMR or EPR spectroscopy, DFT calculations, and SC‐XRD studies. The latter revealed the connection between bond orders in the ligand scaffold and its oxidation state. The paramagnetic compound Me2BPI‐K2 was isolated as a coordination copolymer with 18‐crown‐6, which enabled the characterization of the dianionic BPI radical. Furthermore, the so‐far unknown trianionic state of BPI was reported by the isolation of BPI‐K3. This divulges an unprecedented bis(amidinato)isoindolide coordination mode.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Bis(pyridylimino)isoindolide Alkali Metal Complexes in Three Redox States

2023

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“…Examples of redox-active ligands used in WO catalysis have been reported for Ru-, − Co-, , Ni-, , and Cu-based ,,− , catalysts. The utilization of redox-active ligands in combination with Cu sites has led to the formulation of a variety of alternative mechanistic pathways via which WO is expected to occur . In all of these pathways, single-electron transfer (SET) from an incoming hydroxide ion to the oxidized catalytic intermediate takes a central role.…”

Section: Introductionmentioning

confidence: 99%

“…The utilization of redox-active ligands in combination with Cu sites has led to the formulation of a variety of alternative mechanistic pathways via which WO is expected to occur. 92 In all of these pathways, single-electron transfer (SET) from an incoming hydroxide ion to the oxidized catalytic intermediate takes a central role. In the literature, this reaction step is often indicated as SET-WNA but thus far has predominantly been shown to occur upon attack of a hydroxide ion; hence, we prefer a SET-HA (hydroxide attack) terminology.…”

Section: Introductionmentioning

confidence: 99%

Unusual Water Oxidation Mechanism via a Redox-Active Copper Polypyridyl Complex

et al. 2023

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To improve Cu-based water oxidation (WO) catalysts, a proper mechanistic understanding of these systems is required. In contrast to other metals, high-oxidation-state metal–oxo species are unlikely intermediates in Cu-catalyzed WO because π donation from the oxo ligand to the Cu center is difficult due to the high number of d electrons of CuII and CuIII. As a consequence, an alternative WO mechanism must take place instead of the typical water nucleophilic attack and the inter- or intramolecular radical–oxo coupling pathways, which were previously proposed for Ru-based catalysts. [CuII(HL)(OTf)2] [HL = Hbbpya = N,N-bis(2,2′-bipyrid-6-yl)amine)] was investigated as a WO catalyst bearing the redox-active HL ligand. The Cu catalyst was found to be active as a WO catalyst at pH 11.5, at which the deprotonated complex [CuII(L –)(H2O)]+ is the predominant species in solution. The overall WO mechanism was found to be initiated by two proton-coupled electron-transfer steps. Kinetically, a first-order dependence in the catalyst, a zeroth-order dependence in the phosphate buffer, a kinetic isotope effect of 1.0, a ΔH ⧧ value of 4.49 kcal·mol–1, a ΔS ⧧ value of −42.6 cal·mol–1·K–1, and a ΔG ⧧ value of 17.2 kcal·mol–1 were found. A computational study supported the formation of a Cu–oxyl intermediate, [CuII(L •)(O•)(H2O)]+. From this intermediate onward, formation of the O–O bond proceeds via a single-electron transfer from an approaching hydroxide ion to the ligand. Throughout the mechanism, the CuII center is proposed to be redox-inactive.

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“…TyrÀ Z is heavily involved in the cycle and acts as an electron transfer mediator in each oxidation reaction path. [16,19] The catalytic water oxidation core of OEC in photosystem II consists of a manganese-oxo cluster, [Mn 4 O 5 Ca]. The crystal structure of OEC was investigated at a resolution of 1.9 Å.…”

Section: Introduction Of Photosystem IImentioning

confidence: 99%

“…The OEC undergoes five redox states (Kok cycle) to continuously accumulate the required oxidizing equivalents and eventually releases O 2 , as shown in Figure 2. Tyr−Z is heavily involved in the cycle and acts as an electron transfer mediator in each oxidation reaction path [16,19] …”

Section: Introductionmentioning

confidence: 99%

Rational Design of Electrocatalysts for Water Oxidation Reaction: Inspiration from Photosystem II

Li,

Lang,

Liu

et al. 2023

ChemCatChem

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To address the ever‐increasing societal demand for clean energy, electrocatalytic water splitting has attracted considerable interest for the efficient production of H2 and O2. However, the oxygen evolution reaction (OER) is inherently sluggish and poses significant challenge to the overall water splitting process. As a result, extensive research efforts have been dedicated to pursuing various approaches in developing efficient electrocatalysts for water oxidation. The oxygen‐evolving center (OEC) of Photosystem II (PS II) is a natural model giving the prominent reference. Hence, this review discusses the recent advances in the design of artificial electrocatalyst inspired by PS II. The discussion begins with a brief introduction to the fundamentals of electrocatalytic water oxidation and PS II. Subsequently, the progress of the novel electrocatalysts inspired by PS II is presented in the following two aspects: engineering various transition metal clusters to mimic the inorganic metal cluster of OEC (Mn4O5Ca), and utilizing different ligands to simulate the protein and amino acid environment around [Mn4O5Ca]. In addition to outlying the structures, catalytic activity, and corresponding mechanisms of these prepared catalysts, this present review concludes by proposing several effective development perspectives to this emerging field that warrant further investigation.

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Redox-active ligands in artificial photosynthesis: a review

Cited by 8 publications

References 188 publications

Synthesis and Characterization of Bis(pyridylimino)isoindolide Alkali Metal Complexes in Three Redox States

Synthesis and Characterization of Bis(pyridylimino)isoindolide Alkali Metal Complexes in Three Redox States

Unusual Water Oxidation Mechanism via a Redox-Active Copper Polypyridyl Complex

Rational Design of Electrocatalysts for Water Oxidation Reaction: Inspiration from Photosystem II

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