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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, 7720-7730 p.Article 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, 3257-3260 p.Article 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, 1382-1388 p.Article 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, 12544-12557 p.Article 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, 4907-4911 p.Article 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, 5227-5230 p.Article 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
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, 2090-2101 p.Article 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
Fluch, U., Paneta, V., Primetzhofer, D. & Ott, S. (2017). Uniform distribution of post-synthetic linker exchange in metal-organic frameworks revealed by Rutherford backscattering spectrometry. Chemical Communications, 53(48), 6516-6519.
Open this publication in new window or tab >>Uniform distribution of post-synthetic linker exchange in metal-organic frameworks revealed by Rutherford backscattering spectrometry
2017 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 48, 6516-6519 p.Article in journal (Refereed) Published
Abstract [en]

Rutherford backscattering spectrometry (RBS) has been used for the first time to study post-synthetic linker exchange (PSE) in metal-organic frameworks. RBS is a non-invasive method to quantify the amount of introduced linker, as well as providing a means for depth profiling in order to identify the preferred localization of the introduced linker. The exchange of benzenedicarboxylate (bdc) by similarly sized 2-iodobenzenedicarboxylate (I-bdc) proceeds considerably slower than migration of I-dbc through the UiO-66 crystal. Consequently, the I-bdc is found evenly distributed throughout the UiO-66 samples, even at very short PSE exposure times.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-329662 (URN)10.1039/c7cc02631e (DOI)000403211300032 ()28573305 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyEU, European Research Council, ERC-CoG2015-681895_MOFcatSwedish Foundation for Strategic Research , RIF-140053
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2017-12-28Bibliographically approved
Esfandiarfard, K., Mai, J. & Ott, S. (2017). Unsymmetrical E-Alkenes from the Stereoselective Reductive Coupling of Two Aldehydes. Journal of the American Chemical Society, 139(8), 2940-2943.
Open this publication in new window or tab >>Unsymmetrical E-Alkenes from the Stereoselective Reductive Coupling of Two Aldehydes
2017 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 8, 2940-2943 p.Article in journal (Refereed) Published
Abstract [en]

The unprecedented formation of unsymmetrical alkenes from the intermolecular reductive coupling of two different aldehydes is described. In contrast to the McMurry reaction which affords statistical product mixtures, selectivity in the reported procedure is achieved by a sequential ionic mechanism in which a first aldehyde is reacted with a phosphanylphosphonate to afford a phosphaalkene intermediate which, upon activation by hydroxide, reacts with a second aldehyde to the unsymmetrical E-alkenes. The described reaction is free of transition metals and proceeds under ambient temperature within minutes in good to excellent overall yields. It is a new methodology to use feedstock aldehydes for the direct production of C=C double bond-containing products and may impact how chemists think of multistep synthetic sequences in the future.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-320411 (URN)10.1021/jacs.7b00428 (DOI)000395493400021 ()28186736 (PubMedID)
Funder
Swedish Research Council
Available from: 2017-04-19 Created: 2017-04-19 Last updated: 2017-08-21Bibliographically approved
Johnson, B. A., Maji, S., Agarwala, H., White, T. A., Mijangos, E. & Ott, S. (2016). Activating a Low Overpotential CO2 Reduction Mechanism by a Strategic Ligand Modification on a Ruthenium Polypyridyl Catalyst. Angewandte Chemie International Edition, 55(5).
Open this publication in new window or tab >>Activating a Low Overpotential CO2 Reduction Mechanism by a Strategic Ligand Modification on a Ruthenium Polypyridyl Catalyst
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2016 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 5Article in journal (Refereed) Published
Abstract [en]

The introduction of a simple methyl substituent on the bipyridine ligand of [Ru(tBu(3)tpy)(bpy)(NCCH3)](2+) (tBu(3)tpy = 4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine; bpy = 2,2'-bipyridine) gives rise to a highly active electrocatalyst for the reduction of CO2 to CO. The methyl group enables CO2 binding already at the one-electron reduced state of the complex to enter a previously not accessible catalytic cycle that operates at the potential of the first reduction. The complex turns over with a Faradaic efficiency close to unity and at an overpotential that is amongst the lowest ever reported for homogenous CO2 reduction catalysts.

Keyword
carbon dioxide reduction, electrocatalysis, overpotential, reaction mechanisms, ruthenium
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-280898 (URN)10.1002/anie.201508490 (DOI)000369854000042 ()26671836 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationWenner-Gren Foundations
Available from: 2016-03-16 Created: 2016-03-16 Last updated: 2017-11-30Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-1691-729X

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