Light-driven wateroxidation with a molecular tetra-cobalt(iii) cubanecluster

Ganga, Giuseppina La; Puntoriero, Fausto; Campagna, Sebastiano; Bazzan, Irene; Berardi, Serena; Bonchio, Marcella; Sartorel, Andrea; Natali, Mirco; Scandola, Franco

doi:10.1039/c1fd00093d

Cited by 113 publications

(151 citation statements)

References 74 publications

(46 reference statements)

Supporting

Mentioning

138

Contrasting

Order By: Relevance

“…1b). A similar bell-shaped profile was already observed with a tetracobalt cubane catalyst, 12 and abatement of the rate of O 2 production at >100 mM cobalt concentration was indeed noted also with other molecular precatalysts. 6c This behavior is related to competitive unproductive routes amplified at high catalyst concentration, and likely identifiable with quenching of the Ru(bpy) 3 2+ excited state by CoSlp and by its intermediates involved in the catalytic cycle.…”

supporting

confidence: 78%

Light driven water oxidation by a single site cobalt salophen catalyst

et al. 2013

Self Cite

View full text Add to dashboard Cite

A salophen cobalt(II) complex enables water oxidation at neutral pH in photoactivated sacrificial cycles under visible light, thus confirming the high appeal of earth abundant single site catalysis for artificial photosynthesis.Inspired by the natural Mn 4 CaO x oxygen evolving centre in photosystem II, 1 remarkable efforts have been dedicated towards the development of multinuclear transition metal complexes enabling water oxidation for artificial photosynthesis. 2,3 Multimetallic catalysts could in principle distribute the oxidation equivalents necessary for water oxidation over several metal centres, thus lowering the energy barrier of the overall catalytic process. 3 However, the design of multi-metallic cores with oxygen evolving activity poses synthetic and stability hurdles. Noteworthily, single site metal complexes have been recently discovered, whose oxygen evolving activity offers a major opportunity to broaden the catalyst space within fundamental coordination chemistry. 4 Of particular interest are the earth-abundant cobalt complexes featuring polydentate organic ligands, such as corroles, polypyridines, porphyrins, and polyamines, which have been used under dark electrocatalysis conditions, 5 and in few cases also within photoactivated cycles. 6 Ligand diversity is expected to play a crucial role in tuning photocatalytic water oxidation, with the urgent quest to both optimize sequential photoinduced electron transfer and facilitate the dark-phase of the catalytic mechanism under a turnover regime.In this communication we present a cobalt(II) complex with a salophen ligand (N,N 0 -bis(salicylaldehyde)-1,2-phenylenediamine), ) as the sacrificial electron acceptor (Scheme 1). Combined UV-vis, dynamic light scattering (DLS) and Electron Paramagnetic Resonance (EPR) evidence identifies CoSlp as a competent oxygen evolving catalyst (OEC), enabling a two-fold photoinduced electron transfer in the ms time-frame. Our results confirm the ''privileged'' nature of the salophen ligand environment, readily available from simple condensation reactions, with wide applicability in different fields of catalysis, including bioinspired oxidations. CoSlp is obtained by direct reaction of cobalt acetate with the salophen ligand in methanol, followed by precipitation with diethyl ether and recrystallization.8 † Its solid state and solution identity was initially verified using FT-IR and UV-vis spectroscopy through comparison with literature data (Fig. S2 and S3, ESI †), 8 then confirmed using ESI-MS, where a base peak at m/z = 374 was observed, ascribed to the [CoSlpÁH] + ion (Fig. S4, ESI †). In the solid state, the cobalt ion in CoSlp displays a square planar geometry, 8c while in aqueous solution it extends the coordination sphere to square pyramidal, by ligation of a water molecule in the apical position. 8d Spectrophotometric titration yields a pK a = 6.40 for the aquo ligand (Fig. S5, ESI †), 9 which is therefore expected to be deprotonated at neutral pH, turning into a hydroxo moiety. Characterisation of CoSlp by...

show abstract

supporting

confidence: 78%

Light driven water oxidation by a single site cobalt salophen catalyst

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…40 2 water-oxidation catalysts have also been tested under photocatalytic conditions, usually using the sacrificial electron acceptor S2O8 2-and a molecular photosensitizer (PS) such as [Ru(bpy)3] 2+ or a derivative thereof. 6,7,23,28, Under such conditions, the TOF is generally much lower (< 1 s -1 ) than that obtained by CAN-driven chemical oxidation (> 300 s -1 ). 7,28, More importantly, the stability of photocatalytic systems is also lower (generally TON < 300, compared to >> 1000 for CAN-based systems), 7,28, which, independently of the nature of the catalyst, can be attributed to the decomposition of the photosensitizer.…”

Section: Introductionmentioning

confidence: 87%

Rate and Stability of Photocatalytic Water Oxidation using [Ru(bpy)₃]²⁺ as Photosensitizer

2016

View full text Add to dashboard Cite

The kinetics of homogeneous photocatalytic water oxidation is reported using [Ru(bpy)3]Cl2 as photosensitizer, Na2S2O8 as sacrificial electron acceptor, and three different water-oxidation catalysts: the ruthenium catalyst [Ru(bda)(isoq)2] ([1], H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid, isoq = isoquinoline), Co(NO3)2 ([2]), or [Ir(Cp*)(dmiz)(OH)2] ([3], Cp* = pentamethylcyclopentadienyl, dmiz = 1,3-dimethylimidazol-2-ylidene). At pH=7.0, in a phosphate buffer, and under blue light irradiation, the production of O2 at the catalyst is rate determining when [2] or [3] are used as water-oxidation catalysts. However, when [1] is used as catalyst in identical conditions the turn over at the wateroxidation catalyst is not the rate-limiting step of the photocatalysis. Instead, the step limiting dioxygen production is the transfer of electrons from the catalyst to the photooxidized photosensitizer [Ru(bpy)3] 3+ . Due to the instability of [Ru(bpy)3] 3+ in neutral aqueous solutions, slow electron transfer results in significant photosensitizer decomposition, which limits the overall stability of the photocatalytic system. When the catalyst [1] is used decomposition of both the photosensitizer and the catalyst [1] occurs in parallel. However, the photosensitizer and the catalyst also stabilize each other, i.e., the TON increases when more photosensitizer is added, while the photocatalytic turnover number PTON increases when more catalyst [1] is added. These data demonstrate that not only new and more stable water oxidation catalysts should be developed in the future, but that new and more stable photosensitizers are needed as well.

show abstract

“…[7] The Ca ion in the PSII-WOC has been excluded for clarity (M ¼ Mn or Co). (2) Frei and earlier workers' Co 3 O 4 spinel catalysts (B-site), [9] (3) Spiccia and Hocking's MnO 2 birnessite, [10] (4) Hill's recently discovered Co-polyoxotungstate catalyst, [11]y (5) Dismuke's l-MnO 2 spinel (B-site), [12] as well as (6) [1,2,13] Fig. 1 illustrates these similarities.…”

Section: Introductionmentioning

confidence: 75%

Towards Hydrogen Energy: Progress on Catalysts for Water Splitting

et al. 2012

View full text Add to dashboard Cite

This article reviews some of the recent work by fellows and associates of the Australian Research Council Centre of Excellence for Electromaterials Science (ACES) at Monash University and the University of Wollongong, as well as their collaborators, in the field of water oxidation and reduction catalysts. This work is focussed on the production of hydrogen for a hydrogen-based energy technology. Topics include: (1) the role and apparent relevance of the cubane-like structure of the Photosystem II Water Oxidation Complex (PSII-WOC) in non-biological homogeneous and heterogeneous water oxidation catalysts, (2) light-activated conducting polymer catalysts for both water oxidation and reduction, and (3) porphyrin-based light harvesters and catalysts.

show abstract

Light-driven wateroxidation with a molecular tetra-cobalt(iii) cubanecluster

Cited by 113 publications

References 74 publications

Light driven water oxidation by a single site cobalt salophen catalyst

Light driven water oxidation by a single site cobalt salophen catalyst

Rate and Stability of Photocatalytic Water Oxidation using [Ru(bpy)₃]²⁺ as Photosensitizer

Towards Hydrogen Energy: Progress on Catalysts for Water Splitting

Contact Info

Product

Resources

About

Light-driven wateroxidation with a molecular tetra-cobalt(iii) cubanecluster

Cited by 113 publications

References 74 publications

Light driven water oxidation by a single site cobalt salophen catalyst

Light driven water oxidation by a single site cobalt salophen catalyst

Rate and Stability of Photocatalytic Water Oxidation using [Ru(bpy)3]2+ as Photosensitizer

Towards Hydrogen Energy: Progress on Catalysts for Water Splitting

Contact Info

Product

Resources

About

Rate and Stability of Photocatalytic Water Oxidation using [Ru(bpy)₃]²⁺ as Photosensitizer