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Ahlquist, Mårten S. G.ORCID iD iconorcid.org/0000-0002-1553-4027
Alternative names
Publications (10 of 56) Show all publications
Ahlquist, M. S. G. & Marcos-Escartin, R. (2018). Bicarbonate hydrogenation by iron: Effects of solvent and ligand on the mechanism. 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, LA. Abstract of Papers of the American Chemical Society, 255
Open this publication in new window or tab >>Bicarbonate hydrogenation by iron: Effects of solvent and ligand on the mechanism
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
AMER CHEMICAL SOC, 2018
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-232278 (URN)000435539900119 ()
Conference
255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, LA
Note

QC 20180718

Available from: 2018-07-18 Created: 2018-07-18 Last updated: 2018-07-18Bibliographically approved
Zhan, S. & Ahlquist, M. S. G. (2018). Dynamics and Reactions of Molecular Ru Catalysts at Carbon Nanotube-Water Interfaces. Journal of the American Chemical Society, 140(24), 7498-7503
Open this publication in new window or tab >>Dynamics and Reactions of Molecular Ru Catalysts at Carbon Nanotube-Water Interfaces
2018 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 140, no 24, p. 7498-7503Article in journal (Refereed) Published
Abstract [en]

Immobilization of molecular catalysts to electrode surfaces can improve the recyclability and electron transfer rates. The drawback is that most experimental techniques and theoretical methods are not applicable. Here we present results from a study of a ruthenium water oxidation catalyst [(RuO)-O-V(bda)L-2] in explicit water at a carbon nanotube water interface, forming the key O-O bond between two 128 atom catalysts, all fully dynamically. Our methodology is based on a recently developed empirical valence bond (EVB) model. We follow the key steps of the reaction including diffusion of the catalysts at the interface, formation of the prereactive dimer, and the bond formation between the two catalysts. On the basis of the calculated parameters, we compute the turnover frequency (TOF) at the experimental loading, in excellent agreement with the experiments. The key O-O bond formation was significantly retarded at the surface, and limiting components were identified that could be improved by catalyst modification.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-232254 (URN)10.1021/jacs.8b00433 (DOI)000436211600026 ()29798669 (PubMedID)2-s2.0-85047638616 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20180720

Available from: 2018-07-20 Created: 2018-07-20 Last updated: 2018-07-20Bibliographically approved
Zhan, S., Zou, R. & Ahlquist, M. S. G. (2018). Dynamics with Explicit Solvation Reveals Formation of the Prereactive Dimer as Sole Determining Factor for the Efficiency of Ru(bda)L-2 Catalysts. ACS Catalysis, 8(9), 8642-8648
Open this publication in new window or tab >>Dynamics with Explicit Solvation Reveals Formation of the Prereactive Dimer as Sole Determining Factor for the Efficiency of Ru(bda)L-2 Catalysts
2018 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 8, no 9, p. 8642-8648Article in journal (Refereed) Published
Abstract [en]

This report describes all key steps in the O-O bond formation from two separated [Ru-V=O(bda)L-2](+) cations to form the dinuclear [(bda)L2RuIV-O-Ru-IV(bda)L-2](2+) in explicit solvent. The three steps involve the diffusion of the catalysts in the water phase, formation of the prereactive dimer, and the bond formation between the two catalysts. On the basis of the calculated parameters, we compute the rate constant of two catalysts with different L-ligands, isoquinoline and picoline, and the computed values are in excellent agreement with the experimental ones. The interaction of the axial ligands is key to the improved rates of the larger ligand, mainly by facilitating the formation of the prereactive dimer from the solvated monomer. By comparing the binding free energy of hydrophilic Ru-IV-OH and hydrophobic Ru-V=O, the hydrophobic driving force of Ru-V=O in this system has been estimated to 1 kcal mol(-1).

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
water oxidation, binding free energy, diffusion rate, O-O bond formation, rate constant, molecular dynamics, empirical valence bond
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-235594 (URN)10.1021/acscatal.8b02519 (DOI)000444364800095 ()2-s2.0-85052393349 (Scopus ID)
Note

QC 20181001

Available from: 2018-10-01 Created: 2018-10-01 Last updated: 2018-10-01Bibliographically approved
Marcos, R., Bertini, F., Rinkevicius, Z., Peruzzini, M., Gonsalvi, L. & Ahlquist, M. S. G. (2018). Mechanistic Studies on NaHCO3 Hydrogenation and HCOOH Dehydrogenation Reactions Catalysed by a Fe-II Linear Tetraphosphine Complex. Chemistry - A European Journal, 24(20), 5366-5372
Open this publication in new window or tab >>Mechanistic Studies on NaHCO3 Hydrogenation and HCOOH Dehydrogenation Reactions Catalysed by a Fe-II Linear Tetraphosphine Complex
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2018 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 20, p. 5366-5372Article in journal (Refereed) Published
Abstract [en]

We present a theoretical extension of the previously published bicarbonate hydrogenation to formate and formic acid dehydrogenation catalysed by Fe-II complexes bearing the linear tetraphosphine ligand tetraphos-1. The hydrogenation reaction was found to proceed at the singlet surface with two competing pathways: A)H-2 association to the Fe-H species followed by deprotonation to give a Fe(H)(2) intermediate, which then reacts with CO2 to give formate. B)CO2 insertion into the Fe-H bond, followed by H-2 association and subsequent deprotonation. B was found to be slightly preferred with an activation energy of 22.8kcalmol(-1), compared to 25.3 for A. Further we have reassigned the Fe-H complex, as a Fe(H)(H-2), which undergoes extremely rapid hydrogen exchange.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
catalysis, CO2 hydrogenation, density functional theory, iron, reaction mechanisms
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-227226 (URN)10.1002/chem.201704927 (DOI)000429703700044 ()29243870 (PubMedID)2-s2.0-85040864758 (Scopus ID)
Note

QC 20180521

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2018-05-21Bibliographically approved
Daniel, Q., Duan, L., Timmer, B. J. J., Chen, H., Luo, X., Ambre, R., . . . Sun, L. (2018). Water Oxidation Initiated by In Situ Dimerization of the Molecular Ru(pdc) Catalyst. ACS Catalysis, 8(5), 4375-4382
Open this publication in new window or tab >>Water Oxidation Initiated by In Situ Dimerization of the Molecular Ru(pdc) Catalyst
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2018 (English)In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 8, no 5, p. 4375-4382Article in journal (Refereed) Published
Abstract [en]

The mononuclear ruthenium complex [Ru(pdc)L-3] (H(2)pdc = 2,6-pyridinedicarboxylic acid, L = N-heterocycles such as 4-picoline) has previously shown promising catalytic efficiency toward water oxidation, both in homogeneous solutions and anchored on electrode surfaces. However, the detailed water oxidation mechanism catalyzed by this type of complex has remained unclear. In order to deepen understanding of this type of catalyst, in the present study, [Ru(pdc)(py)(3)] (py = pyridine) has been synthesized, and the detailed catalytic mechanism has been studied by electrochemistry, UV-vis, NMR, MS, and X-ray crystallography. Interestingly, it was found that once having reached the Ru-IV state, this complex promptly formed a stable ruthenium dimer [Ru-III(pdc)(py)(2)-O-Ru-IV(pdc)(py)(2)](+). Further investigations suggested that the present dimer, after one pyridine ligand exchange with water to form [Ru-III(pdc)(py)(2)-O-Ru-IV(pdc)(py)(H2O)](+), was the true active species to catalyze water oxidation in homogeneous solutions.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
solar fuels, water oxidation, electrochemistry, ruthenium dimer, mechanism of O-O bond formation
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-231630 (URN)10.1021/acscatal.7b03768 (DOI)000431727300070 ()2-s2.0-85046695744 (Scopus ID)
Note

QC 20180702

Available from: 2018-07-02 Created: 2018-07-02 Last updated: 2018-07-02Bibliographically approved
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, p. 6962-6965Article 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-VCH Verlagsgesellschaft, 2017
Keywords
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)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20170620

Available from: 2017-06-20 Created: 2017-06-20 Last updated: 2018-02-27Bibliographically 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, p. 1748-1751Article 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
Keywords
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, p. 2607-2615Article 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
Keywords
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 ()2-s2.0-85019738559 (Scopus ID)
Note

QC 20170509

Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2018-09-19Bibliographically 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 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, 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, 2017
Keywords
Water oxidation, EPR, Ruthenium, Coordination, DFT
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: 2018-02-27Bibliographically 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, p. 2956-2966Article 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
Keywords
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
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ORCID iD: ORCID iD iconorcid.org/0000-0002-1553-4027

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