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Styring, Stenbjörn
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Publications (10 of 109) Show all publications
Kjmer, K. S., Kaul, N., Prakash, O., Chabera, P., Rosemann, N. W., Honarfar, A., . . . Wärnmark, K. (2019). Luminescence and reactivity of a charge-transfer excited iron complex with nanosecond lifetime. Science, 363(6424), 249-253
Open this publication in new window or tab >>Luminescence and reactivity of a charge-transfer excited iron complex with nanosecond lifetime
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2019 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 363, no 6424, p. 249-253Article in journal (Refereed) Published
Abstract [en]

Iron's abundance and rich coordination chemistry are potentially appealing features for photochemical applications. However, the photoexcitable charge-transfer states of most iron complexes are limited by picosecond or subpicosecond deactivation through low-lying metal-centered states, resulting in inefficient electron-transfer reactivity and complete lack of photoluminescence. In this study, we show that octahedral coordination of iron(Ill) by two mono-anionic facial tris-carbene ligands can markedly suppress such deactivation. The resulting complex [Fe(phtmeimb)(2)](+), where phtmeimb is {phenyl[tris(3-methylimidazol-1-ylidene)]borate}(-), exhibits strong, visible, room temperature photoluminescence with a 2.0-nanosecond lifetime and 2% quantum yield via spin-allowed transition from a doublet ligand-to-metal charge-transfer ((LMCT)-L-2) state to the doublet ground state. Reductive and oxidative electron-transfer reactions were observed for the (2)LMCTstate of [Fe(phtmeimb)(2)](+) in bimolecular quenching studies with methylviologen and diphenylamine.

Place, publisher, year, edition, pages
AMER ASSOC ADVANCEMENT SCIENCE, 2019
National Category
Theoretical Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-376883 (URN)10.1126/science.aau7160 (DOI)000456140700029 ()30498167 (PubMedID)
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationSwedish National Infrastructure for Computing (SNIC)Stiftelsen Olle Engkvist ByggmästareCarl Tryggers foundation Wenner-Gren FoundationsThe Crafoord Foundation
Available from: 2019-02-12 Created: 2019-02-12 Last updated: 2019-02-12Bibliographically approved
Schuth, N., Zaharieva, I., Chernev, P., Berggren, G., Anderlund, M., Styring, S., . . . Haumann, M. (2018). K alpha X-ray Emission Spectroscopy on the Photosynthetic Oxygen-Evolving Complex Supports Manganese Oxidation and Water Binding in the S-3 State. Inorganic Chemistry, 57(16), 10424-10430
Open this publication in new window or tab >>K alpha X-ray Emission Spectroscopy on the Photosynthetic Oxygen-Evolving Complex Supports Manganese Oxidation and Water Binding in the S-3 State
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2018 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 16, p. 10424-10430Article in journal (Refereed) Published
Abstract [en]

The unique manganese calcium-catalyst in photosystem II (PSII) is the natural paragon for efficient light driven water oxidation to yield O-2. The oxygen-evolving complex (OEC) in the dark-stable state (S-1) comprises a Mn4CaO4 core with five metal-bound water species. Binding and modification of the water molecules that are substrates of the water-oxidation reaction is mechanistically crucial but controversially debated. Two recent crystal structures of the OEC in its highest oxidation state (S-3) show either a vacant Mn coordination site or a bound peroxide species. For purified PSII at room temperature, we collected Mn K alpha X-ray emission spectra of the S-0, S-1, S-2, and S-3 intermediates in the OEC cycle, which were analyzed by comparison to synthetic Mn compounds, spectral simulations, and OEC models from density functional theory. Our results contrast both crystallographic structures. They indicate Mn oxidation in three S-transitions and suggest additional water binding at a previously open Mn coordination site. These findings exclude Mn reduction and render peroxide formation in S-3 unlikely.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-364392 (URN)10.1021/acs.inorgchem.8b01674 (DOI)000442489100090 ()30067343 (PubMedID)
Funder
Swedish Energy AgencyKnut and Alice Wallenberg Foundation
Available from: 2018-11-02 Created: 2018-11-02 Last updated: 2018-11-02Bibliographically approved
Magnuson, A., Raleiras, P., Meszaros, L. S., Khanna, N., Miranda, H., Ho, F. M., . . . Styring, S. (2018). Sustainable photobiological hydrogen production via protein engineering of cyanobacterial hydrogenases. Paper presented at 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, USA.. Abstract of Papers of the American Chemical Society, 255
Open this publication in new window or tab >>Sustainable photobiological hydrogen production via protein engineering of cyanobacterial hydrogenases
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2018 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Washington, D.C.: American Chemical Society (ACS), 2018
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-368928 (URN)000435539900440 ()
Conference
255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, USA.
Note

Meeting Abstract: 443

Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-11Bibliographically approved
Pavlou, A., Jacques, J., Ahmadova, N., Mamedov, F. & Styring, S. (2018). The wavelength of the incident light determines the primary charge separation pathway in Photosystem II. Scientific Reports, 8, Article ID 2837.
Open this publication in new window or tab >>The wavelength of the incident light determines the primary charge separation pathway in Photosystem II
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 2837Article in journal (Refereed) Published
Abstract [en]

Charge separation is a key component of the reactions cascade of photosynthesis, by which solar energy is converted to chemical energy. From this photochemical reaction, two radicals of opposite charge are formed, a highly reducing anion and a highly oxidising cation. We have previously proposed that the cation after far-red light excitation is located on a component different from P-D1, which is the location of the primary electron hole after visible light excitation. Here, we attempt to provide further insight into the location of the primary charge separation upon far-red light excitation of PS II, using the EPR signal of the spin polarized P-3(680) as a probe. We demonstrate that, under far-red light illumination, the spin polarized P-3(680) is not formed, despite the primary charge separation still occurring at these conditions. We propose that this is because under far-red light excitation, the primary electron hole is localized on Chl(D1), rather than on P-D1. The fact that identical samples have demonstrated charge separation upon both far-red and visible light excitation supports our hypothesis that two pathways for primary charge separation exist in parallel in PS II reaction centres. These pathways are excited and activated dependent of the wavelength applied.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-348115 (URN)10.1038/s41598-018-21101-w (DOI)000424743500053 ()29434283 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-04-11Bibliographically approved
Chabera, P., Liu, Y., Prakash, O., Thyrhaug, E., El Nahhas, A., Honarfar, A., . . . Warnmark, K. (2017). A low-spin Fe(III) complex with 100-ps ligand-to-metal charge transfer photoluminescence. Nature, 543(7647), 695-+
Open this publication in new window or tab >>A low-spin Fe(III) complex with 100-ps ligand-to-metal charge transfer photoluminescence
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2017 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 543, no 7647, p. 695-+Article in journal (Refereed) Published
Abstract [en]

Transition-metal complexes are used as photosensitizers(1), in light-emitting diodes, for biosensing and in photocatalysis(2). A key feature in these applications is excitation from the ground state to a charge-transfer state(3,4); the long charge-transfer-state lifetimes typical for complexes of ruthenium(5) and other precious metals are often essential to ensure high performance. There is much interest in replacing these scarce elements with Earth-abundant metals, with iron(6) and copper(7) being particularly attractive owing to their low cost and non-toxicity. But despite the exploration of innovative molecular designs(6,8-10), it remains a formidable scientific challenge(11) to access Earth-abundant transition-metal complexes with long-lived charge-transfer excited states. No known iron complexes are considered(12) photoluminescent at room temperature, and their rapid excited-state deactivation precludes their use as photosensitizers(13-15). Here we present the iron complex [Fe(btz)(3)](3+) (where btz is 3,3'-dimethyl-1,1'-bis(p-tolyl)-4,4'-bis(1,2,3-triazol-5-ylidene)), and show that the superior sigma-donor and pi-acceptor electron properties of the ligand stabilize the excited state sufficiently to realize a long charge-transfer lifetime of 100 picoseconds (ps) and room-temperature photoluminescence. This species is a low-spin Fe(III) d(5) complex, and emission occurs from a long-lived doublet ligand-to-metal charge-transfer ((LMCT)-L-2) state that is rarely seen for transition-metal complexes(4,16,17). The absence of intersystem crossing, which often gives rise to large excited-state energy losses in transition-metal complexes, enables the observation of spin-allowed emission directly to the ground state and could be exploited as an increased driving force in photochemical reactions on surfaces. These findings suggest that appropriate design strategies can deliver new iron-based materials for use as light emitters and photosensitizers.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2017
National Category
Chemical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-320033 (URN)10.1038/nature21430 (DOI)000397619700051 ()28358064 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationSwedish Energy AgencyThe Crafoord FoundationSwedish National Infrastructure for Computing (SNIC)Stiftelsen Olle Engkvist Byggmästare
Available from: 2017-04-13 Created: 2017-04-13 Last updated: 2017-04-18Bibliographically approved
Liu, S., Lei, Y.-J., Xin, Z.-J., Xiang, R.-J., Styring, S., Thapper, A. & Wang, H.-Y. (2017). Ligand modification to stabilize the cobalt complexes for water oxidation. International journal of hydrogen energy, 42(50), 29716-29724
Open this publication in new window or tab >>Ligand modification to stabilize the cobalt complexes for water oxidation
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2017 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 42, no 50, p. 29716-29724Article in journal (Refereed) Published
Abstract [en]

Ligand modifications with electron-withdrawing and electron-donating groups were applied to afford three novel mononuclear cobalt-based catalysts [Co(TPA-R)]2+ (TPA = tris(2-pyridylmethyl) amine; R = tri-α F, 1; R = tri-αOMe, 2; R = mono-αF, 3) for water oxidation. Characterization of the catalysts shows that steric and electronic factors play important roles in inhibiting spontaneous intermolecular dimerization of two cobalt centers, and influence the catalytic behavior. Complex 1 exhibits the best catalytic ability and stability, showing a good efficiency with TOF of 6.03 ± 0.02 mol (O2)/(mol (cat)*s) in photo-induced water oxidation experiments using Ru (bpy)3 2+ as photosensitizer and Na2S2O8 as electron acceptor. The bulky electron donating groups in 2 led to degradation of the complex and formation of CoOx particles acting as the real catalyst. Electron-withdrawing substituents on the TPA ligand can stabilize the catalyst under both electrochemical and photo-induced conditions, with the enhancement increasing with the number of the electron-withdrawing groups. © 2017 Hydrogen Energy Publications LLC.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Water oxidation, Photo-induced, Cobalt catalyst, Ligand modification, Catalytic behavior
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-335940 (URN)10.1016/j.ijhydene.2017.10.066 (DOI)000419417600009 ()2-s2.0-85034447058 (Scopus ID)
Funder
Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067
Note

Funding details: Shaanxi Normal University; Funding details: Energimyndigheten; Funding details: National Natural Science Foundation of China; Funding details: Knut och Alice Wallenbergs StiftelseN1 - Funding text: This work is supported by the National Natural Science Foundation of China ( 21402113 ), the Fundamental Research Funds for the Central Universities ( GK201703025 ). AT and SS gratefully acknowledge the Swedish Energy Agency ( 11674-5 ) and the Knut and Alice Wallenberg Foundation ( 2011.0067 ) for funding. We are grateful for Prof. Jing Liu at Shaanxi Normal University to provide DLS instrument. Appendix A

Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-02-16Bibliographically approved
Daniel, Q., Huang, P., Fan, T., Wang, Y., Duan, L., Wang, L., . . . Sun, L. (2017). Rearranging from 6-to 7-coordination initiates the catalytic activity: An EPR study on a Ru-bda water oxidation catalyst. Coordination chemistry reviews, 346, 206-215
Open this publication in new window or tab >>Rearranging from 6-to 7-coordination initiates the catalytic activity: An EPR study on a Ru-bda water oxidation catalyst
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2017 (English)In: Coordination chemistry reviews, ISSN 0010-8545, E-ISSN 1873-3840, Vol. 346, p. 206-215Article, review/survey (Refereed) Published
Abstract [en]

The coordination of a substrate water molecule on a metal centered catalyst for water oxidation is a crucial step involving the reorganization of the ligand sphere. This process can occur by substituting a coordinated ligand with a water molecule or via a direct coordination of water onto an open site. In 2009, we reported an efficient ruthenium-based molecular catalyst, Ru-bda, for water oxidation. Despite the impressive improvement in catalytic activity of this type of catalyst over the past years, a lack of understanding of the water coordination still remains. Herein, we report our EPR and DFT studies on Ru-bda (triethylammonium 3-pyridine sulfonate)(2) (1) at its Ru-III oxidation state, which is the initial state in the catalytic cycle for the O-O bond formation. Our investigation suggests that at this III-state, there is already a rearrangement in the ligand sphere where the coordination of a water molecule at the 7th position (open site) takes place under acidic conditions (pH = 1.0) to form a rare 7-coordinated Ru-III species.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
Water oxidation, EPR, Ruthenium, Coordination, DFT
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-332735 (URN)10.1016/j.ccr.2017.02.019 (DOI)000402873900014 ()
Funder
Swedish Energy AgencyKnut and Alice Wallenberg FoundationSwedish Research Council
Available from: 2017-11-15 Created: 2017-11-15 Last updated: 2017-12-07Bibliographically approved
Sjöholm, J., Ho*, F., Ahmadova, N., Brinkert, K., Hammarström, L., Mamedov*, F. & Styring, S. (2017). The protonation state around Tyr(D)/Tyr((D)) over dot in photosystem II is reflected in its biphasic oxidation kinetics. Biochimica et Biophysica Acta - Bioenergetics, 1858(2), 147-155
Open this publication in new window or tab >>The protonation state around Tyr(D)/Tyr((D)) over dot in photosystem II is reflected in its biphasic oxidation kinetics
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2017 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 2, p. 147-155Article in journal (Refereed) Published
Abstract [en]

The tyrosine residue D2-Tyr160 (Tyr(D)) in photosystem II (PSII) can be oxidized through charge equilibrium with the oxygen evolving complex in PSII. The kinetics of the electron transfer from Tyr(D) has been followed using time resolved EPR spectroscopy after triggering the oxidation of pre-reduced Tyr(D) by a short laser flash. After its oxidation Tyro is observed as a neutral radical (Tyr((D)) over dot) indicating that the oxidation is coupled to a deprotonation event. The redox state of Tyro was reported to be determined by the two water positions identified in the crystal structure of PSII [Saito et al. (2013) Proc. Natl. Acad. Sci. USA 110, 7690]. To assess the mechanism of the proton coupled electron transfer of Tyr(D) the oxidation kinetics has been followed in the presence of deuterated buffers, thereby resolving the kinetic isotope effect (KIE) of Tyro oxidation at different H/D concentrations. Two kinetic phases of Tyro oxidation - the fast phase (msec-sec time range) and the slow phase (tens of seconds time range) were resolved as was previously reported [Vass and Styring (1991) Biochemistry 30, 830]. In the presence of deuterated buffers the kinetics was significantly slower compared to normal buffers. Furthermore, although the kinetics were faster at both high pH and pD values the observed KIE was found to be similar (similar to 2.4) over the whole pL range investigated. We assign the fast and slow oxidation phases to two populations of PSII centers with different water positions, proximal and distal respectively, and discuss possible deprotonation events in the vicinity of Tyro.

Keywords
Photosystem II, Tyrosine D, Electron transfer, Proton transfer, Deuterium isotope effect
National Category
Biochemistry and Molecular Biology Biophysics
Identifiers
urn:nbn:se:uu:diva-316938 (URN)10.1016/j.bbabio.2016.11.002 (DOI)000392776400007 ()27823941 (PubMedID)
Funder
Swedish Research Council, 621-2013-5937Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, KAW 2011.0067
Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2017-04-30
Ahmadova, N., Ho, F., Styring, S. & Mamedov, F. (2017). Tyrosine D oxidation and redox equilibrium in Photosystem II. Biochimica et Biophysica Acta - Bioenergetics, 1858(6), 407-417
Open this publication in new window or tab >>Tyrosine D oxidation and redox equilibrium in Photosystem II
2017 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 6, p. 407-417Article in journal (Refereed) Published
Abstract [en]

Tyrosine ID (Tyr(D)) is an auxiliary redox active tyrosine residue in photosystem II (PSII). The mechanism of Tyr(D) oxidation was investigated by EPR spectroscopy, flash-induced fluorescence decay and thermoluminescence measurements in PSII enriched membranes from spinach. PSII membranes were chemically treated with 3 mM ascorbate and 1 mM diaminodurene and subsequent washing, leading to the complete reduction of Tyr(D). Tyr(D) oxidation kinetics and competing recombination reactions were measured after a single saturating flash in the absence and presence of DCMU (inhibitor of the Q(B)-site) in the pH range of 4.7-8.5. Two kinetic phases of Tyro oxidation were observed by the time resolved EPR spectroscopy the fast phase (msec-sec time range) and the pH dependent slow phase (tens of seconds time range). In the presence of DCMU, Tyr(D) oxidation kinetics was monophasic in the entire pH range, i.e. only the fast kinetics was observed. The results obtained from the fluorescence and thermoluminescence analysis show that when forward electron transport is blocked in the presence of DCMU, the S(2)Q((S) over bar) recombination outcompetes the slow phase of Tyr(D) oxidation by the S-2 state. Modelling of the whole complex of these electron transfer events associated with Tyr(D) oxidation fitted very well with our experimental data. Based on these data, structural information and theoretical considerations we confirm our assignment of the fast and slow oxidation kinetics to two populations of PSII centers with different water positions (proximal and distal) in the Tyr(D) vicinity.

Keywords
Photosystem II, Electron transfer, Tyrosine D
National Category
Natural Sciences
Research subject
Biochemistry
Identifiers
urn:nbn:se:uu:diva-320913 (URN)10.1016/j.bbabio.2017.02.011 (DOI)000402349000001 ()28235460 (PubMedID)
Funder
Swedish Research Council, 621-2013-5937Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067
Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2017-07-06Bibliographically approved
Pavliuk, M. V., Mijangos, E., Makhankova, V. G., Kokozay, V. N., Pullen, S., Liu, J., . . . Thapper, A. (2016). Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation. ChemSusChem, 9(20), 2957-2966
Open this publication in new window or tab >>Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation
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2016 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 9, no 20, p. 2957-2966Article in journal (Refereed) Published
Abstract [en]

The heterometallic complexes (NH4)2[Co(H2O)6]2[V10O28]·4H2O (1) and (NH4)2[Co(H2O)5(β-HAla)]2[V10O28]·4H2O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (<500 °C) leads to the formation of the solid mixed oxides CoV2O6/V2O5 (3) and Co2V2O7/V2O5 (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO2 film. The electrodes containing Co/V MMOs in TiO2 films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mA cm−2 at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO2 films with MMOs at relatively low temperatures (<500 °C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis.

Keywords
cobalt, heterogeneous catalysis, mixed oxides, synthesis design, water oxidation
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Molecular Biomimetics
Identifiers
urn:nbn:se:uu:diva-306375 (URN)10.1002/cssc.201600769 (DOI)000386953500011 ()
Funder
Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation, 2011.0067Swedish Institute, 00284/2013
Available from: 2016-10-27 Created: 2016-10-27 Last updated: 2017-11-29Bibliographically approved
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