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Johnson, B. A., Bhunia, A., Fei, H., Cohen, S. M. & Ott, S. (2018). Development of a UiO-Type Thin Film Electrocatalysis Platform with Redox-Active Linkers. Journal of the American Chemical Society, 140(8), 2985-2994
Open this publication in new window or tab >>Development of a UiO-Type Thin Film Electrocatalysis Platform with Redox-Active Linkers
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2018 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 140, no 8, p. 2985-2994Article in journal (Refereed) Published
Abstract [en]

Metal–organic frameworks (MOFs) as electrocatalysis scaffolds are appealing due to the large concentration of catalytic units that can be assembled in three dimensions. To harness the full potential of these materials, charge transport to the redox catalysts within the MOF has to be ensured. Herein, we report the first electroactive MOF with the UiO/PIZOF topology (Zr(dcphOH-NDI)), i.e., one of the most widely used MOFs for catalyst incorporation, by using redox-active naphthalene diimide-based linkers (dcphOH-NDI). Hydroxyl groups were included on the dcphOH-NDI linker to facilitate proton transport through the material. Potentiometric titrations of Zr(dcphOH-NDI) show the proton-responsive behavior via the −OH groups on the linkers and the bridging Zr-μ3-OH of the secondary building units with pKa values of 6.10 and 3.45, respectively. When grown directly onto transparent conductive fluorine-doped tin oxide (FTO), 1 μm thin films of Zr(dcphOH-NDI)@FTO could be achieved. Zr(dcphOH-NDI)@FTO displays reversible electrochromic behavior as a result of the sequential one-electron reductions of the redox-active NDI linkers. Importantly, 97% of the NDI sites are electrochemically active at applied potentials. Charge propagation through the thin film proceeds through a linker-to-linker hopping mechanism that is charge-balanced by electrolyte transport, giving rise to cyclic voltammograms of the thin films that show characteristics of a diffusion-controlled process. The equivalent diffusion coefficient, De, that contains contributions from both phenomena was measured directly by UV/vis spectroelectrochemistry. Using KPF6 as electrolyte, De was determined to be De(KPF6) = (5.4 ± 1.1) × 10–11 cm2 s–1, while an increase in countercation size to n-Bu4N+ led to a significant decrease of De by about 1 order of magnitude (De(n-Bu4NPF6) = (4.0 ± 2.5) × 10–12 cm2 s–1).

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-351270 (URN)10.1021/jacs.7b13077 (DOI)000426617700044 ()29421875 (PubMedID)
Funder
Swedish Research Council
Available from: 2018-06-04 Created: 2018-06-04 Last updated: 2018-06-04Bibliographically approved
Schlotthauer, T., Parada, G. A., Goerls, H., Ott, S., Jaeger, M. & Schubert, U. S. (2017). Asymmetric Cyclometalated RuII Polypyridyl-Type Complexes with Π-Extended Carbanionic Donor Sets. Inorganic Chemistry, 56(14), 7720-7730
Open this publication in new window or tab >>Asymmetric Cyclometalated RuII Polypyridyl-Type Complexes with Π-Extended Carbanionic Donor Sets
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2017 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 14, p. 7720-7730Article in journal (Refereed) Published
Abstract [en]

A series of novel cyclometalated Ru-II complexes were investigated featuring the tridentate dqp ligand platform (dqp is 2,6-di(quinolin-8-yl)pyridine), in order to utilize the octahedral coordination mode around the Ru center to modulate the electrochemical and photophysical properties. The heteroleptic complexes feature C-1 symmetry due to symmetry breaking by the peripheral five- or six-membered carbanionic chelate (phenyl, naphthyl, or anthracenyl units). The chelation mode is controlled by the steric effects and C-H activation selectivity of the ligand, which prompted the development of a general synthesis protocol. The optimized conditions to achieve high overall yields (55-75%) involve NaHCO3 as the base and an simplified purification protocol: i.e., facile chromatographic separation using commercially available amino-functionalized silica applying nonaqueous salt-free conditions to omit the necessity of counterion exchange. The structural, photophysical, and electrochemical properties were studied in depth, and the results were corroborated by density functional theory (DFT) calculations. Steady state and time-resolved spectroscopy revealed red-shifted absorption (up to 750 run) and weak IR emission (800-1000 nm) combined with prolonged emission lifetimes (up to 20 ns) in comparison to classical tpy-based (tpy is 2,2':6',2 ''-terpyridine) complexes. An enhanced stability was observed by blocking the reactive positions of the carbanionic ligand framework, while the reactive positions may be exploited for further functionalization.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-332419 (URN)10.1021/acs.inorgchem.7b00392 (DOI)000405972200018 ()
Funder
Swedish Energy AgencyKnut and Alice Wallenberg Foundation
Note

Title in WoS: Asymmetric Cyclometalated Ru-II Polypyridyl-Type Complexes with pi-Extended Carbanionic Donor Sets

Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2017-12-28Bibliographically approved
Roy, S., Pascanu, V., Pullen, S., Gonzalez Miera, G., Martin-Matute, B. & Ott, S. (2017). Catalyst accessibility to chemical reductants in metal–organic frameworks. Chemical Communications, 53(22), 3257-3260
Open this publication in new window or tab >>Catalyst accessibility to chemical reductants in metal–organic frameworks
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2017 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 22, p. 3257-3260Article in journal (Refereed) Published
Abstract [en]

A molecular H2-evolving catalyst, [Fe2(cbdt)(CO)6] ([FeFe], cbdt = 3-carboxybenzene-1,2-dithiolate), has been attached covalently to an amino-functionalized MIL-101(Cr) through an amide bond. Chemical reduction experiments reveal that the MOF channels can be clogged by ion pairs that are formed between the oxidized reductant and the reduced catalyst. This effect is lessened in MIL-101-NH-[FeFe] with lower [FeFe] loadings. On longer timescales, it is shown that large proportions of the [FeFe] catalysts within the MOF engage in photochemical hydrogen production and the amount of produced hydrogen is proportional to the catalyst loading.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-318972 (URN)10.1039/c7cc00022g (DOI)000398998500023 ()28261731 (PubMedID)
Available from: 2017-03-29 Created: 2017-03-29 Last updated: 2017-12-28Bibliographically approved
Johnson, B. A., Bhunia, A. & Ott, S. (2017). Electrocatalytic water oxidation by a molecular catalyst incorporated into a metal-organic framework thin film. Dalton Transactions, 46(5), 1382-1388
Open this publication in new window or tab >>Electrocatalytic water oxidation by a molecular catalyst incorporated into a metal-organic framework thin film
2017 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 5, p. 1382-1388Article in journal (Refereed) Published
Abstract [en]

A molecular water oxidation catalyst, [Ru(tpy)(dcbpy)(OH2)](ClO4)(2) (tpy = 2,2': 6',2''-terpyridine, dcbpy = 2,2'-bipyridine- 5,5'-dicarboxylic acid) [1], has been incorporated into FTO-grown thin films of UiO-67 (UiO = University of Oslo), by post-synthetic ligand exchange. Cyclic voltammograms (0.1 M borate buffer at pH = 8.4) of the resulting UiO67-[RuOH2]@ FTO show a reversible wave associated with the Ru-III/II couple in the anodic scan, followed by a large current response that arises from electrocatalytic water oxidation beyond 1.1 V vs. Ag/AgCl. Water oxidation can be observed at an applied potential of 1.5 V over the timescale of hours with a current density of 11.5 mu A cm(-2). Oxygen evolution was quantified in situ over the course of the experiment, and the Faradaic efficiency was calculated as 82%. Importantly, the molecular integrity of [1] during electrocatalytic water oxidation is maintained even on the timescale of hours under turnover conditions and applied voltage, as evidenced by the persistence of the wave associated with the Ru-III/II couple in the CV. This experiment highlights the capability of metal organic frameworks like UiO-67 to stabilize the molecular structure of catalysts that are prone to form higher clusters in homogenous phase.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-319681 (URN)10.1039/c6dt03718frsc.li/dalton (DOI)000395442700005 ()27845800 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation
Available from: 2017-04-07 Created: 2017-04-07 Last updated: 2017-11-29Bibliographically approved
Kositzki, R., Mebs, S., Schuth, N., Leidel, N., Schwartz, L., Karnahl, M., . . . Haumann, M. (2017). Electronic and molecular structure relations in diiron compounds mimicking the [FeFe]-hydrogenase active site studied by X-ray spectroscopy and quantum chemistry. Dalton Transactions, 46(37), 12544-12557
Open this publication in new window or tab >>Electronic and molecular structure relations in diiron compounds mimicking the [FeFe]-hydrogenase active site studied by X-ray spectroscopy and quantum chemistry
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2017 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 37, p. 12544-12557Article in journal (Refereed) Published
Abstract [en]

Synthetic diiron compounds of the general formula Fe-2(mu-S2R)(CO)(n)(L)(6-n) (R = alkyl or aromatic groups; L = CN- or phosphines) are versatile models for the active-site cofactor of hydrogen turnover in [FeFe]-hydrogenases. A series of 18 diiron compounds, containing mostly a dithiolate bridge and terminal ligands of increasing complexity, was characterized by X-ray absorption and emission spectroscopy in combination with density functional theory. Fe K-edge absorption and K beta main-line emission spectra revealed the varying geometry and the low-spin state of the Fe(I) centers. Good agreement between experimental and calculated core-to-valence-excitation absorption and radiative valence-to-core-decay emission spectra revealed correlations between spectroscopic and structural features and provided access to the electronic configuration. Four main effects on the diiron core were identified, which were preferentially related to variation either of the dithiolate or of the terminal ligands. Alteration of the dithiolate bridge affected mainly the Fe-Fe bond strength, while more potent donor substitution and ligand field asymmetrization changed the metal charge and valence level localization. In contrast, cyanide ligation altered all relevant properties and, in particular, the frontier molecular orbital energies of the diiron core. Mutual benchmarking of experimental and theoretical parameters provides guidelines to verify the electronic properties of related diiron compounds.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-336431 (URN)10.1039/c7dt02720f (DOI)000411702300022 ()28905949 (PubMedID)
Available from: 2017-12-15 Created: 2017-12-15 Last updated: 2017-12-15Bibliographically approved
Mijangos, E., Roy, S., Pullen, S., Lomoth, R. & Ott, S. (2017). Evaluation of two- and three-dimensional electrode platforms for the electrochemical characterization of organometallic catalysts incorporated in non-conducting metal-organic frameworks. Dalton Transactions, 46(15), 4907-4911
Open this publication in new window or tab >>Evaluation of two- and three-dimensional electrode platforms for the electrochemical characterization of organometallic catalysts incorporated in non-conducting metal-organic frameworks
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2017 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 15, p. 4907-4911Article in journal (Refereed) Published
Abstract [en]

The development of a reliable platform for the electrochemical characterization of a redox-active molecular diiron complex, [FeFe], immobilized in a non-conducting metal organic framework (MOF), UiO-66, based on glassy-carbon electrodes is reported. Voltammetric data with appreciable current responses can be obtained by the use of multiwalled carbon nanotubes (MWCNT) or mesoporous carbon (CB) additives that function as conductive scaffolds to interface the MOF crystals in "three-dimensional" electrodes. In the investigated UiO-66-[FeFe] sample, the low abundance of [FeFe] in the MOF and the intrinsic insulating properties of UiO-66 prevent charge transport through the framework, and consequently, only [FeFe] units that are in direct physical contact with the electrode material are electrochemically addressable.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Inorganic Chemistry Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-321800 (URN)10.1039/c7dt00578d (DOI)000398888700006 ()28345708 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationWenner-Gren FoundationsEU, European Research Council, ERC-CoG2015-681895_MOFcat
Available from: 2017-05-11 Created: 2017-05-11 Last updated: 2017-05-11Bibliographically approved
Pullen, S., Roy, S. & Ott, S. (2017). [FeFe] Hydrogenase active site model chemistry in a UiO-66metal-organic framework. Chemical Communications, 53(37), 5227-5230
Open this publication in new window or tab >>[FeFe] Hydrogenase active site model chemistry in a UiO-66metal-organic framework
2017 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 37, p. 5227-5230Article in journal (Refereed) Published
Abstract [en]

The reactivity of [Fe-2(dcbdt)(CO)(6)] (1) confined in a UiO-66(Zr) metal-organic framework towards CO ligand substitutions with phosphines of different sizes was investigated. The reaction with smaller phosphines (PX3, X = Me, Et) is more selective compared to analogous reactions in homogenous solution phase, and two CO ligands at up to 80% of all [FeFe] sites in UiO-66-1 are replaced. The produced [Fe-2(dcbdt)(CO)(4)(PX3)(2)] complexes in the UiO-66 matrix behave like typical [FeFe] hydrogenase active site model complexes, are reduced at more cathodic potentials than their hexacarbonyl analogues, and form bridging hydrides under acidic conditions.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-325338 (URN)10.1039/c7cc01620d (DOI)000400858400038 ()28443863 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyWenner-Gren FoundationsEU, European Research Council, ERC-CoG2015-681895_MOFcat
Available from: 2017-06-29 Created: 2017-06-29 Last updated: 2017-06-29Bibliographically approved
Bedin, M., Agarwala, H., Ott, S. & Thapper, A. (2017). Heterometallic Mn/Fe complexes versus homometallic Mn/Mn and Fe/Fe complexes as models for the dimetal carboxylate cofactors.. Paper presented at 18th International Conference on Biological Inorganic Chemistry (ICBIC), JUL 31-AUG 04, 2017, Florianópolis, Brazil. Journal of Biological Inorganic Chemistry, 22(Supplement: 1), S38-S38
Open this publication in new window or tab >>Heterometallic Mn/Fe complexes versus homometallic Mn/Mn and Fe/Fe complexes as models for the dimetal carboxylate cofactors.
2017 (English)In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 22, no Supplement: 1, p. S38-S38Article in journal, Meeting abstract (Other academic) Published
Keywords
RNR, Iron-Manganese, Heterobimetallic complexes
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-350095 (URN)10.1007/s00775-017-1475-y (DOI)000419606600007 ()
Conference
18th International Conference on Biological Inorganic Chemistry (ICBIC), JUL 31-AUG 04, 2017, Florianópolis, Brazil
Available from: 2018-05-04 Created: 2018-05-04 Last updated: 2018-05-04Bibliographically approved
Pavliuk, M. V., Cieślak,, A. M., Abdellah, M., Budinská, A., Pullen, S., Sokolowski, K., . . . Sá, J. (2017). Hydrogen evolution with nanoengineered ZnO interfaces decorated using a beetroot extract and a hydrogenase mimic. Sustainable Energy & Fuels, 1, 69-73
Open this publication in new window or tab >>Hydrogen evolution with nanoengineered ZnO interfaces decorated using a beetroot extract and a hydrogenase mimic
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2017 (English)In: Sustainable Energy & Fuels, ISSN 2398-4902, Vol. 1, p. 69-73Article in journal (Refereed) Published
Abstract [en]

Herein, we report a nano-hybrid photo-system based on abundant elements for H2 production with visible light. The photo-system's proficiency relates to the novel ZnO nanocrystals employed. The ZnO carboxylate oligoethylene glycol shell enhances charge separation and accumulates reactive electrons for the photocatalytic process. 

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
Keywords
H2 evolution
National Category
Physical Chemistry Engineering and Technology
Research subject
Chemistry with specialization in Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-335979 (URN)10.1039/c6se00066e (DOI)000422769100006 ()
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-04-03Bibliographically approved
Glover, S. D., Parada, G. A., Markle, T. F., Ott, S. & Hammarström, L. (2017). Isolating the Effects of the Proton Tunneling Distance on Proton-Coupled Electron Transfer in a Series of Homologous Tyrosine-Base Model Compounds. Journal of the American Chemical Society, 139(5), 2090-2101
Open this publication in new window or tab >>Isolating the Effects of the Proton Tunneling Distance on Proton-Coupled Electron Transfer in a Series of Homologous Tyrosine-Base Model Compounds
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2017 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 5, p. 2090-2101Article in journal (Refereed) Published
Abstract [en]

The distance dependence of concerted proton-coupled electron transfer (PCET) reactions was probed in a series of three new compounds, where a phenol is covalently bridged by a 5, 6, or 7 membered carbocycle to the quinoline. The carbocycle bridge enforces the change in distance between the phenol oxygen (proton donor) and quinoline nitrogen (proton acceptor), d(O center dot center dot center dot N), giving rise to values ranging from 2.567 to 2.8487 angstrom, and resulting in calculated proton tunneling distances, r(0), that span 0.719 to 1.244 angstrom. Not only does this series significantly extend the range of distances that has been previously accessible for experimental distance dependent PCET studies of synthetic model compounds, but it also greatly improves the isolation of d(O center dot center dot center dot N) as a variable compared to earlier reports. Rates of PCET were determined by time-resolved optical spectroscopy with flash-quench generated [Ru(bpy)(3)](3+) and [Ru(dce)(3)](3+), where bpy = 2,2'-bipyridyl and dce = 4,4'-dicarboxyethylester-2,2'-bipyridyl. The rates increased as d(O center dot center dot center dot N) decreased, as can be expected from a static proton tunneling model. An exponential attenuation of the PCET rate constant was found: k(PCET)(d) = k(PCET)(0)exp[-beta(d-d(0))], with beta similar to 10 angstrom(-1). The observed kinetic isotope effect (KIE = k(H)/k(D)) ranged from 1.2 to 1.4, where the KIE was observed to decrease slightly with increasing d(O center dot center dot center dot N). Both beta and KIE values are significantly smaller than what is predicted by a static proton tunneling model. We conclude that vibrational compression of the tunneling distances, as well as higher vibronic transitions, that contribute to concerted proton coupled electron transfer must also be considered.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-319098 (URN)10.1021/jacs.6b12531 (DOI)000393848400060 ()28052668 (PubMedID)
Funder
Swedish Research Council, 623-2011-7189 2012-4060-97215-39Swedish Energy Agency, 11674-5Knut and Alice Wallenberg Foundation
Available from: 2017-04-03 Created: 2017-04-03 Last updated: 2017-12-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-1691-729X

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