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BETA
Ahlquist, Mårten S. G.ORCID iD iconorcid.org/0000-0002-1553-4027
Alternative names
Publications (10 of 51) Show all publications
Zhan, S., Mårtensson, D., Purg, M., Kamerlin, S. C. L. & Ahlquist, M. S. G. (2017). Capturing the Role of Explicit Solvent in the Dimerization of Ru-V(bda) Water Oxidation Catalysts. Angewandte Chemie International Edition, 56(24), 6962-6965.
Open this publication in new window or tab >>Capturing the Role of Explicit Solvent in the Dimerization of Ru-V(bda) Water Oxidation Catalysts
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2017 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, no 24, 6962-6965 p.Article in journal (Refereed) Published
Abstract [en]

A ground-breaking empirical valence bond study for a soluble transition-metal complex is presented. The full reaction of catalyst monomers approaching and reacting in the Ru-V oxidation state were studied. Analysis of the solvation shell in the reactant and along the reaction coordinate revealed that the oxo itself is hydrophobic, which adds a significant driving force to form the dimer. The effect of the solvent on the reaction between the prereactive dimer and the product was small. The solvent seems to lower the barrier for the isoquinoline (isoq) complex while it is increased for pyridines. By comparing the reaction in the gas phase and solution, the proposed p-stacking interaction of the isoq ligands is found to be entirely driven by the water medium.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keyword
diradical coupling reaction, empirical valence bond, hydrophobic oxo, solvation effect, water oxidation
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-209064 (URN)10.1002/anie.201701488 (DOI)000402523900049 ()28493633 (PubMedID)2-s2.0-85019990678 (Scopus ID)
Note

QC 20170620

Available from: 2017-06-20 Created: 2017-06-20 Last updated: 2017-06-20Bibliographically approved
Ahlstrand, D. A., Polukeev, A. V., Marcos, R., Ahlquist, M. S. G. & Wendt, O. F. (2017). Csp(3)-H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products. Chemistry - A European Journal, 23(8), 1748-1751.
Open this publication in new window or tab >>Csp(3)-H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products
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2017 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 8, 1748-1751 p.Article in journal (Refereed) Published
Abstract [en]

Cyclometallation of 8-methylquinoline and 2-(dimethylamino)-pyridine in an iridium-based pincer complex is described. The C-H activation of 2-(dimethylamino) pyridine is not chelation assisted, which has not been described before for Csp(3)-H bonds in cyclometallation reactions. The mechanism of the cyclometallation of 2-(dimethylamino) pyridine was studied by DFT calculations and kinetic measurements.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keyword
cyclometallation, density functional calculations, iridium, pincer complexes, undirected C-H activation
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-205092 (URN)10.1002/chem.201604469 (DOI)000395754800003 ()27982473 (PubMedID)
Note

QC 20170626

Available from: 2017-06-26 Created: 2017-06-26 Last updated: 2017-06-26Bibliographically approved
Kagalwala, H. N., Tong, L., Zong, R., Kohler, L., Ahlquist, M. S. G., Fan, T., . . . Thummel, R. P. (2017). Evidence for Oxidative Decay of a Ru-Bound Ligand during Catalyzed Water Oxidation. ACS Catalysis, 7(4), 2607-2615.
Open this publication in new window or tab >>Evidence for Oxidative Decay of a Ru-Bound Ligand during Catalyzed Water Oxidation
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2017 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 4, 2607-2615 p.Article in journal (Refereed) Published
Abstract [en]

In the evaluation of systems designed for 800 catalytic water oxidation, ceric ammonium nitrate (CAN) is often used as a sacrificial electron acceptor. One of the sources of failure for such systems is oxidative decay of the catalyst in the presence of the strong oxidant CAN (E-ox = +1.71 V). Little progress has been made in understanding the circumstances behind this decay. In this study we show that a 2-(2'-hydroxphenyl) derivative (LH) of 1,10-phenanthroline (phen) in the complex [Ru(L)(tpy)](+) (tpy = 2,2';6',2 ''-terpyridine) can be oxidized by CAN to a 2-carboxy-phen while still bound to the metal. This complex is, in fact, a very active water oxidation catalyst. The incorporation of a methyl substituent on the phenol ring of LH slows down the oxidative decay and consequently slows down the catalytic oxidation. An analogous system based on bpy (2,2'-bipyridine) instead of phen shows much lower activity under the same conditions. Water molecule association to the Ru center of [Ru(L)(tpy)](+) and carboxylate donor dissociation were proposed to occur at the trivalent state. The resulting [Ru-III-OH2] was further oxidized to [Ru-IV=O] via a PCET process.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
Keyword
mononuclear Ru catalysts, water oxidation, anionic ligands, 2-carboxyphenanthroline, ligand decay
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-206687 (URN)10.1021/acscatal.6b03278 (DOI)000398986700045 ()
Note

QC 20170509

Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2017-05-09Bibliographically 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, 206-215 p.Article in journal (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, wereported an efficient ruthenium-based molecular catalyst, Ru-bda, for water oxidation. Despite theimpressive 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 RuIII oxidation state, which is the initial state inthe catalytic cycle for the O–O bond formation. Our investigation suggests that at this III-state, there isalready 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 RuIII species

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-207807 (URN)10.1016/j.ccr.2017.02.019 (DOI)000402873900014 ()2-s2.0-85014846790 (Scopus ID)
Funder
Swedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20170608

Available from: 2017-05-24 Created: 2017-05-24 Last updated: 2017-11-10Bibliographically approved
Fan, T., Duan, L., Huang, P., Chen, H., Daniel, Q., Ahlquist, M. S. G. & Sun, L. (2017). The Ru-tpc Water Oxidation Catalyst and Beyond: Water Nucleophilic Attack Pathway versus Radical Coupling Pathway.. ACS Catalysis, 7(4), 2956-2966.
Open this publication in new window or tab >>The Ru-tpc Water Oxidation Catalyst and Beyond: Water Nucleophilic Attack Pathway versus Radical Coupling Pathway.
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2017 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 4, 2956-2966 p.Article in journal (Refereed) Published
Abstract [en]

Many Ru water oxidation catalysts have been documented in the literature. However, only a few can catalyze the O-O bond formation via the radical coupling pathway, while most go through the water nucleophilic attack pathway. Understanding the electronic effect on the reaction pathway is of importance in design of active water oxidation catalysts. The Ru-bda (bda = 2,2'-bipyridine-6,6'-dicarboxylate) catalyst is one example that catalyzes the 0-0 bond formation via the radical coupling pathway. Herein, we manipulate the equatorial backbone ligand, change the doubly charged bda(2-) ligand to a singly charged tpc- (2,2':6',2 ''-terpyridine-6-carboxylate) ligand, and study the structure activity relationship. Surprisingly, kinetics measurements revealed that the resulting Ru-tpc catalyst catalyzes water oxidation via the water nucleophilic attack pathway, which is different from the Ru-bda catalyst. The O-O bond formation Gibbs free energy of activation (AGO) at T = 298.15 K was 20.2 +/- 1.7 kcal mol(-1). The electronic structures of a series of Ru-v=O species were studied by density function theory calculations, revealing that the spin density of O-Ru=O of Ru-v=O is largely dependent on the surrounding ligands. Seven coordination configuration significantly enhances the radical character of Ru-v=O.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
Keyword
water oxidation, ruthenium complex, artificial photosynthesis, DFT calculation, water splitting
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-206688 (URN)10.1021/acscatal.6b03393 (DOI)000398986700082 ()
Note

QC 20170509

Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2017-05-09Bibliographically approved
Wang, Y., Montoya, J. H., Tsai, C., Ahlquist, M. S. G., Norskov, J. K. & Studt, F. (2016). Scaling Relationships for Binding Energies of Transition Metal Complexes. Catalysis Letters, 146(2), 304-308.
Open this publication in new window or tab >>Scaling Relationships for Binding Energies of Transition Metal Complexes
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2016 (English)In: Catalysis Letters, ISSN 1011-372X, E-ISSN 1572-879X, Vol. 146, no 2, 304-308 p.Article in journal (Refereed) Published
Abstract [en]

In this work, we investigate the trends in binding energies of different reaction intermediates on transition metal complexes for homogeneous catalysis. We find that linear scaling relationships exist between the binding energies of N and NHx (x = 1, 2), analogous to the bond-order formulation well-known in heterogeneous catalysis. This approach provides a new perspective of reactivity trends in transition metal complexes and opens up the possibility of using a descriptor-based approach for investigating homogeneous catalysis. We show the first steps towards this analysis by analyzing a wide range of modified "Schrock-type" catalysts.

Place, publisher, year, edition, pages
Springer, 2016
Keyword
Homogeneous catalysis, Density functional theory, Scaling relations, N-2 reduction, Molybdenum
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-183325 (URN)10.1007/s10562-015-1667-4 (DOI)000370076200003 ()2-s2.0-84958113668 (Scopus ID)
Note

QC 20160309

Available from: 2016-03-09 Created: 2016-03-07 Last updated: 2017-11-30Bibliographically approved
Polukeev, A. V., Marcos, R., Ahlquist, M. S. G. & Wendt, O. F. (2016). Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium. Chemistry - A European Journal, 22(12), 4078-4086.
Open this publication in new window or tab >>Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium
2016 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 12, 4078-4086 p.Article in journal (Refereed) Published
Abstract [en]

The hydride iridium pincer complex [(PCyP)IrH2] (PCyP=cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane, 1) reveals remarkably solvent-dependent hydride chemical shifts, isotope chemical shifts, J(HD) and T-1(min), with r(HH) increasing upon moving to more polar medium. The only known example of such behaviour (complex [(POCOP)IrH2], POCOP=2,6-(tBu(2)PO)(2)C6H3) was explained by the coordination of a polar solvent molecule to the iridium (J. Am. Chem. Soc. 2006, 128, 17114). Based on the existence of an agostic bond between -C-H and iridium in 1 in all solvents, we argue that the coordination of solvent can be rejected. DFT calculations revealed that the structures of 1 and [(POCOP)IrH2] depend on the dielectric permittivity of the medium and these compounds adopt trigonal-bipyramidal geometries in non-polar media and square-pyramidal geometries in polar media.

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2016
Keyword
density functional calculations, hydrides, iridium, pincer complexes, solvent effects
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-185640 (URN)10.1002/chem.201505133 (DOI)000372526500025 ()26880293 (PubMedID)2-s2.0-84959866485 (Scopus ID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20160427

Available from: 2016-04-27 Created: 2016-04-25 Last updated: 2017-11-30Bibliographically approved
Fan, T., Zhan, S. & Ahlquist, M. S. G. (2016). Why Is There a Barrier in the Coupling of Two Radicals in the Water Oxidation Reaction?. ACS Catalysis, 6(12), 8308-8312.
Open this publication in new window or tab >>Why Is There a Barrier in the Coupling of Two Radicals in the Water Oxidation Reaction?
2016 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, no 12, 8308-8312 p.Article in journal (Refereed) Published
Abstract [en]

Two radicals can form a bond without an energetic barrier. However, the radical coupling mechanism in ruthenium catalyzed water oxidation has been found to be associated with substantial activation energies. Here we have investigated the coupling reaction of [Ru=O(bda)L-2](+) catalysts with different axial L ligands. The interaction between the two oxo radical moieties at the Ru(V) state was found to have a favorable interaction in the transition state in comparison to the prereactive complex. To further understand the existence of the activation energy, the activation energy has been decomposed into distortion energy and interaction energy. No correlation between the experimental rates and the calculated coupling barriers of different axial L was found, showing that more aspects such as solvation, supramolecular properties, and solvent dynamics likely play important roles in the equilibrium between the free Ru-v=0 monomer and the [Ru-v=O center dot center dot center dot O=Ru-v] dimer. On the basis of our findings, we give general guidelines for the design of catalysts that operate by the radical coupling mechanism.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keyword
water oxidation, radical coupling, I2M, DFT, bda, catalysis, ruthenium
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-199489 (URN)10.1021/acscatal.6b02697 (DOI)000389399400034 ()
Note

QC 20170119

Available from: 2017-01-19 Created: 2017-01-09 Last updated: 2017-11-29Bibliographically approved
Wang, Y., Duan, L., Wang, L., Chen, H., Sun, J., Sun, L. & Ahlquist, M. S. G. (2015). Alkene Epoxidation Catalysts [Ru(pdc)(tpy)] and [Ru(pdc)(pybox)] Revisited: Revealing a Unique Ru-IV=O Structure from a Dimethyl Sulfoxide Coordinating Complex. ACS Catalysis, 5(7), 3966-3972.
Open this publication in new window or tab >>Alkene Epoxidation Catalysts [Ru(pdc)(tpy)] and [Ru(pdc)(pybox)] Revisited: Revealing a Unique Ru-IV=O Structure from a Dimethyl Sulfoxide Coordinating Complex
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2015 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 7, 3966-3972 p.Article in journal (Refereed) Published
Abstract [en]

The X-ray crystal structure of a dimethyl sulfoxide (DMSO) coordinating complex [Ru-II(kappa(2)-pdc)(tpy)(DMSO)] (H(2)pdc = 2,6-pyridyl dicarboxylic acid and tpy = 2,2':6',2 ''-terpyridine) led to the discovery of a unique Ru-IV=O configuration for the Ru-pybox (pybox = pyridine-bis(oxazoline) ligands) epoxidation catalyst by theoretical calculations. On the basis of this structure, a detailed theoretical study was conducted on the alkene epoxidation reaction using ruthenium-based epoxidation catalysts. It was found that the process of H2O2 coordination proceeded via an associative path in which one carboxylate detached. The following H2O-elimination step was found to be facilitated by the detached carboxylate group. The resulting Ru-IV=O rearranges to the species trans-2a-oxo, in which one carboxylate group is situated over the tpy ring; the trans-2a-oxo was found to have the lowest activation free energies toward alkene epoxidation. These results demonstrated the importance of the hemilabile properties of the pdc(2-) ligand for the Ru-pdc alkene epoxidation catalysts.

Keyword
epoxidation, ruthenium, DFT, hemilabile, oxidation, mechanism
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-171896 (URN)10.1021/acscatal.5b00496 (DOI)000357626800008 ()2-s2.0-84946130418 (Scopus ID)
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation
Note

QC 20150812

Available from: 2015-08-12 Created: 2015-08-10 Last updated: 2017-12-04Bibliographically approved
Polukeev, A. V., Marcos, R., Ahlquist, M. S. G. & Wendt, O. F. (2015). Formation of a C-C double bond from two aliphatic carbons. Multiple C-H activations in an iridium pincer complex. Chemical Science, 6(3), 2060-2067.
Open this publication in new window or tab >>Formation of a C-C double bond from two aliphatic carbons. Multiple C-H activations in an iridium pincer complex
2015 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 6, no 3, 2060-2067 p.Article in journal (Refereed) Published
Abstract [en]

The search for novel, atom-economic methods for the formation of C-C bonds is of crucial importance in synthetic chemistry. Especially attractive are reactions where C-C bonds are formed through C-H activation, but the coupling of unactivated, alkane-type C-sp3-H bonds remains an unsolved challenge. Here, we report iridium-mediated intramolecular coupling reactions involving up to four unactivated C-sp3-H bonds to give carbon-carbon double bonds under the extrusion of dihydrogen. The reaction described herein is completely reversible and the direction can be controlled by altering the reaction conditions. With a hydrogen acceptor present a C-C double bond is formed, while reacting under dihydrogen pressure leads to the reverse process, with some of the steps representing net C-sp3-C-sp3 bond cleavage. Mechanistic investigations revealed a conceptually-novel overall reactivity pattern where insertion or deinsertion of an Ir carbene moiety, formed via double C-H activation, into an Ir-C bond is responsible for the key C-C bond formation and cleavage steps.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-161629 (URN)10.1039/c4sc03839h (DOI)000349832600060 ()2-s2.0-84923167393 (Scopus ID)
Note

QC 20150324

Available from: 2015-03-24 Created: 2015-03-13 Last updated: 2017-12-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-1553-4027

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