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  • 1.
    Abdel-Magied, Ahmed F.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Arafa, Wael A. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Substituent Effects in Molecular Ruthenium Water Oxidation Catalysts Based on Amide Ligands2017In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 9, no 9, p. 1583-1587Article in journal (Refereed)
    Abstract [en]

    The production of clean and sustainable energy is considered as one of the most urgent issues for our society. Mastering the oxidation of water to dioxygen is essential for the production of solar fuels. A study of the influence of the substituents on the catalytic activity of a series of mononuclear Ru complexes (2a-e) based on a tetradentate ligand framework is presented. At neutral pH, using [Ru(bpy)(3)](PF6)(3) (bpy=2,2'-bipyridine) as the terminal oxidant, a good correlation between the turnover frequency (TOF) and the Hammett sigma(meta) parameters was obtained. Additionally, a general pathway for the deactivation of Ru-based catalysts 2a-e during the catalytic oxidation of water through poisoning by carbon monoxide was demonstrated. These results highlight the importance of ligand design for fine-tuning the catalytic activity of water oxidation catalysts.

  • 2.
    Abdel-Magied, Ahmed F.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Arafa, Wael A. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University Fayoum, Egypt.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Bjorn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chemical and Photochemical Water Oxidation Mediated by an Efficient Single-Site Ruthenium Catalyst2016In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 9, no 24, p. 3448-3456Article in journal (Refereed)
    Abstract [en]

    Water oxidation is a fundamental step in artificial photosynthesis for solar fuels production. In this study, we report a single-site Ru-based water oxidation catalyst, housing a dicarboxylate-benzimidazole ligand, that mediates both chemical and light-driven oxidation of water efficiently under neutral conditions. The importance of the incorporation of the negatively charged ligand framework is manifested in the low redox potentials of the developed complex, which allows water oxidation to be driven by the mild one-electron oxidant [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine). Furthermore, combined experimental and DFT studies provide insight into the mechanistic details of the catalytic cycle.

  • 3.
    Arafa, Wael A. A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Berends, Hans-Martin
    Messinger, Johannes
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dinuclear manganese complexes for water oxidation: evaluation of electronic effects and catalytic activity2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 24, p. 11950-11964Article in journal (Refereed)
    Abstract [en]

    During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O-2 and solar fuels, such as H-2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn-2 (II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.

  • 4.
    Bosque, Irene
    et al.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Magallanes, Gabriel
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Rigoulet, Mathilde
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Kärkäs, Markus D.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Redox Catalysis Facilitates Lignin Depolymerization2017In: ACS Central Science, ISSN 2374-7951, Vol. 3, no 6, p. 621-628Article in journal (Refereed)
    Abstract [en]

    Lignin is a recalcitrant and underexploited natural feedstock for aromatic commodity chemicals, and its degradation generally requires the use of high temperatures and harsh reaction conditions. Herein we present an ambient temperature one-pot process for the controlled oxidation and depolymerization of this potent resource. Harnessing the potential of electrocatalytic oxidation in conjugation with our photocatalytic cleavage methodology, we have developed an operationally simple procedure for selective fragmentation of β-O-4 bonds with excellent mass recovery, which provides a unique opportunity to expand the existing lignin usage from energy source to commodity chemicals and synthetic building block source.

  • 5. Das, Biswanath
    et al.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Demeshko, Serhiy
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Haukka, Matti
    Zeglio, Erica
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Nuclear Materials Authority, Egypt.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Meyer, Franc
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordlander, Ebbe
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 34, p. 13289-13293Article in journal (Refereed)
    Abstract [en]

    The synthesis of two molecular iron complexes, a dinuclear iron(III,III) complex and a nonanuclear iron complex, based on the di-nucleating ligand 2,2'-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)(3)](3+).

  • 6.
    Gustafson, Karl P. J.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Schluschass, Bastian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation mediated by ruthenium oxide nanoparticles supported on siliceous mesocellular foam2017In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 7, no 1, p. 293-299Article in journal (Refereed)
    Abstract [en]

    Artificial photosynthesis is an attractive strategy for converting solar energy into fuel. In this context, development of catalysts for oxidation of water to molecular oxygen remains a critical bottleneck. Herein, we describe the preparation of a well-defined nanostructured RuO2 catalyst, which is able to carry out the oxidation of water both chemically and photochemically. The developed heterogeneous RuO2 nanocatalyst was found to be highly active, exceeding the performance of most known heterogeneous water oxidation catalysts when driven by chemical or photogenerated oxidants.

  • 7.
    Iqbal, M. Naeem
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Abdel-Magied, Ahmed. F.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Abdelhamid, Hani Nasser
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Olsén, Peter
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Shatskiy, Andrey
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Zou, Xiaodong
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Åkermark, Björn
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Kärkäs, Markus D.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Johnston, Eric V.
    Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Mesoporous Ruthenium Oxide: A Heterogeneous Catalyst for Water Oxidation2017In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, p. 9651-9656Article in journal (Refereed)
    Abstract [en]

    Herein we report the synthesis of mesoporous ruthenium oxide (MP-RuO2) using a template-based approach. The catalytic efficiency of the prepared MP-RuO2 was compared to commercially available ruthenium oxide nanoparticles (C-RuO2) as heterogeneous catalysts for water oxidation. The results demonstrated superior performance of MP-RuO2 for oxygen evolution compared to the C-RuO2 with respect to recyclability, amount of generated oxygen, and stability over several catalytic runs.

  • 8.
    Iqbal, M. Naeem
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Olsén, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mesoporous Ruthenium Oxide: A Heterogeneous Catalyst for Water Oxidation2017In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, no 11, p. 9651-9656Article in journal (Refereed)
    Abstract [en]

    Herein we report the synthesis of mesoporous ruthenium oxide (MP-RuO2) using a template-based approach. The catalytic efficiency of the prepared MP-RuO2 was compared to commercially available ruthenium oxide nanoparticles (C-RuO2) as heterogeneous catalysts for water oxidation. The results demonstrated superior performance of MP-RuO2 for oxygen evolution compared to the C-RuO2 with respect to recyclability, amount of generated oxygen, and stability over several catalytic runs.

  • 9.
    Johnston, Eric V
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Novel dinuclear Ru-complex for water oxidation2010In: Abstracts of Papers, 240th ACS National Meeting, Boston, MA, United States, August 22-26, 2010 (2010), American Chemical Society , 2010Conference paper (Other academic)
  • 10.
    Johnston, Eric V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shakeri, Mozaffar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Palmgren, Pål
    Eriksson, Kristofer
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Oscarsson, Sven
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly dispersed palladium nanoparticles on mesocellular foam: an efficient and recyclable heterogeneous catalyst for alcohol oxidation2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 39, p. 12202-12206Article in journal (Refereed)
  • 11. Karlsson, Erik A.
    et al.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Becerril, Valeria Saavedra
    Abrahamsson, Maria
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and electron transfer processes in a new family of coupled Mn2–Ru complexesManuscript (preprint) (Other academic)
  • 12.
    Karlsson, Erik A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Becerril, Valeria Saavedra
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Abrahamsson, Maria
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and Electron-Transfer Processes in a New Family of Ligands for Coupled Ru-Mn2 Complexes2014In: ChemPlusChem, ISSN 2192-6506, Vol. 79, no 7, p. 936-950Article in journal (Refereed)
    Abstract [en]

    A series of [Ru(bpy)(3)](2+)-type (bpy= 2,2'-bipyridine) photosensitisers have been coupled to a ligand for Mn, which is expected to give a dinuclear complex that is active as a water oxidation catalyst. Unexpectedly, photophysical studies showed that the assemblies had very short lived excited states and that the decay patterns were complex and strongly dependent on pH. One dyad was prepared that was capable of catalysing chemical water oxidation by using [Ru(bpy)(3)](3+) as an oxidant. However, photochemical water oxidation in the presence of an external electron acceptor failed, presumably because the short excited-state lifetime precluded initial electron transfer to the added acceptor. The photophysical behaviour could be explained by the presence of an intricate excited-state manifold, as also suggested by time-dependent DFT calculations.

  • 13.
    Karlsson, Erik A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hansson, Örjan
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Photosensitized water oxidation by use of a bioinspired manganese catalyst2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 49, p. 11715-11718Article in journal (Refereed)
  • 14.
    Kärkäs, Markus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bio-inspired metal complexes: Their synthesis and application in light-driven water oxidation and organic transformations2010Licentiate thesis, comprehensive summary (Other academic)
  • 15.
    Kärkäs, Markus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development and Mechanistic Studies of Molecularly Defined Water Oxidation Catalysts: Catalysts for a Green and Sustainable Future2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the development of complexes that are active catalysts for H2O oxidation. Promoting proton-coupled electron transfer has been a highly important feature in the development of these catalysts.

    The first part deals with the modification of ligand frameworks for the development of a ruthenium complex capable of withstanding the highly oxidizing conditions required for H2O oxidation. 

    The second part of the thesis describes the development of two single-site ruthenium(III) complexes, housing two meridionally coordinating tridentate benzimidazole ligands. Studies on these complexes revealed that they can mediate H2O oxidation, both by the use of a chemical oxidant and photochemically, and that the ligand frameworks were important in promoting proton-coupled electron transfer events.

    In the third part, systematic modifications are introduced into one of the catalysts developed in the second part of the thesis. All of the complexes were shown to be active water oxidation catalysts (WOCs), and kinetic studies confirmed that all catalysts displayed a first-order dependence on catalyst concentration, thereby validating that H2O oxidation occurs on a single metal site. By using linear free-energy relationships it was possible to elucidate the unusual behavior exerted by the ligand framework during the catalytic cycle.

    The fourth part concerns the development of a ruthenium(III) WOC, containing a tetradentate bioinspired ligand architecture, and its deactivation pathway during H2O oxidation catalysis. This revealed an unexplored, and perhaps general, deactivation pathway for ruthenium-based WOCs. Evidence was also found that the ruthenium WOC reaches a high-valent ruthenium(VI) state which is the active species in H2O oxidation.

    Finally, the fifth and last part deals with the development of a dinuclear manganese complex. Utilizing a bioinspired, highly functionalized ligand, enabled the formation of the first homogeneous manganese-based WOC capable of promoting catalytic H2O oxidation with one-electron oxidants.

  • 16.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Electrochemical strategies for C-H functionalization and C-N bond formation2018In: Chemical Society Reviews, ISSN 0306-0012, E-ISSN 1460-4744, Vol. 47, no 15, p. 5786-5865Article, review/survey (Refereed)
    Abstract [en]

    Conventional methods for carrying out carbon-hydrogen functionalization and carbon-nitrogen bond formation are typically conducted at elevated temperatures, and rely on expensive catalysts as well as the use of stoichiometric, and perhaps toxic, oxidants. In this regard, electrochemical synthesis has recently been recognized as a sustainable and scalable strategy for the construction of challenging carbon-carbon and carbon-heteroatom bonds. Here, electrosynthesis has proven to be an environmentally benign, highly effective and versatile platform for achieving a wide range of nonclassical bond disconnections via generation of radical intermediates under mild reaction conditions. This review provides an overview on the use of anodic electrochemical methods for expediting the development of carbon-hydrogen functionalization and carbon-nitrogen bond formation strategies. Emphasis is placed on methodology development and mechanistic insight and aims to provide inspiration for future synthetic applications in the field of electrosynthesis.

  • 17.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Lignin Hydrogenolysis: Improving Lignin Disassembly through Formaldehyde Stabilization2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 10, p. 2111-2115Article, review/survey (Refereed)
    Abstract [en]

    Lignocellulosic biomass is available in large quantities and constitutes an attractive feedstock for the sustainable production of bulk and fine chemicals. Although methods have been established for the conversion of its cellulosic fractions, valorization of lignin has proven to be challenging. The difficulty in disassembling lignin originates from its heterogeneous structure and its propensity to undergo skeletal rearrangements and condensation reactions during biorefinery fractionation or biomass pretreatment processes. A strategy for hindering the generation of these resistive interunit linkages during biomass pretreatment has now been devised using formaldehyde as a stabilizing agent. The developed method when combined with Ru/C‐catalyzed hydrogenolysis allows for efficient disassembly of all three biomass fractions: (cellulose, hemicellulose, and lignin) and suggests that lignin upgrading can be integrated into prevailing biorefinery schemes.

  • 18.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
    Photochemical Generation of Nitrogen-Centered Amidyl, Hydrazonyl, and Imidyl Radicals: Methodology Developments and Catalytic Applications2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, p. 4999-5022Article, review/survey (Refereed)
    Abstract [en]

    During the past decade, visible light photocatalysis has become a powerful synthetic platform for promoting challenging bond constructions under mild reaction conditions. These photocatalytic systems rely on harnessing visible light energy for synthetic purposes through the generation of reactive but controllable free radical species. Recent progress in the area of visible light photocatalysis has established it as an enabling catalytic strategy for the mild and selective generation of nitrogen-centered radicals. The application of visible light for photocatalytic activation of amides, hydrazones, and imides represents a valuable approach for facilitating the formation of nitrogen-centered radicals. Within the span of only a couple of years, significant progress has been made for expediting the generation of amidyl, hydrazonyl, and imidyl radicals from a variety of precursors. This Perspective highlights the recent advances in visible light-mediated generation of these radicals. A particular emphasis is placed on the unique ability of visible light photocatalysis in accessing elusive reaction manifolds for the construction of diversely functionalized nitrogen-containing motifs and as a platform for nontraditional bond disconnections in contemporary synthetic chemistry.

  • 19.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Photochemical Generation of Nitrogen-Centered Amidyl, Hydrazonyl, and Imidyl Radicals: Methodology Developments and Catalytic Applications2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 8, p. 4999-5022Article in journal (Refereed)
    Abstract [en]

    During the past decade, visible light photo catalysis has become a powerful synthetic platform for promoting challenging bond constructions under mild reaction conditions. These photocatalytic systems rely on harnessing visible light energy for synthetic purposes through the generation of reactive but controllable free radical species. Recent progress in the area of visible light photocatalysis has established it as an enabling catalytic strategy for the mild and selective generation of nitrogen-centered radicals. The application of visible light for photocatalytic activation of amides, hydrazones, and imides represents a valuable approach for facilitating the formation of nitrogen-centered radicals. Within the span of only a couple of years, significant progress has been made for expediting the generation of amidyl, hydrazonyl, and imidyl radicals from a variety of precursors. This Perspective highlights the recent advances in visible light-mediated generation of these radicals. A particular emphasis is placed on the unique ability of visible light photocatalysis in accessing elusive reaction manifolds for the construction of diversely functionalized nitrogen-containing motifs and as a platform for nontraditional bond disconnections in contemporary synthetic chemistry.

  • 20.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Bosque, Irene
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Matsuura, Bryan S.
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Photocatalytic Oxidation of Lignin Model Systems by Merging Visible-Light Photoredox and Palladium Catalysis2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 19, p. 5166-5169Article in journal (Refereed)
    Abstract [en]

    Lignin valorization has long been recognized as a sustainable solution for the renewable production of aromatic compounds. Two-step oxidation/reduction strategies, whereby the first oxidation step is required to “activate” lignin systems for controlled fragmentation reactions, have recently emerged as viable routes toward this goal. Herein we describe a catalytic protocol for oxidation of lignin model systems by combining photoredox and Pd catalysis. The developed dual catalytic protocol allowed the efficient oxidation of lignin model substrates at room temperature to afford the oxidized products in good to excellent yields.

  • 21.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Shariatgorji, Mohammadreza
    Ilag, Leopold
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hansson, Örjan
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Light-Induced Water Oxidation by a Ru-complex Containing a Bio-Inspired Ligand2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 28, p. 7953-7959Article in journal (Refereed)
    Abstract [en]

    The new Ru-complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 could efficiently catalyze water oxidation using CeIV and RuIII as chemical oxidants. More importantly, this complex has sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers.

  • 22.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Artificial Photosynthesis: Photosynthesis: From Nanosecond Electron Transfer to Catalytic Water Oxidation2014In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 47, no 1, p. 100-111Article, review/survey (Refereed)
    Abstract [en]

    Human society faces a fundamental challenge as energy consumption is projected to increase due to population and economic growth as fossil fuel resources decrease. Therefore the transition to alternative and sustainable energy sources is of the Utmost importance. The conversion of solar energy into chemical energy, by splitting H2O to generate molecular O-2 and H-2, could contribute to solving the global energy problem. Developing such a system will require the combination of several complicated processes, such as light-harvesting, charge separation, electron transfer, H2O oxidation, and reduction of the generated protons. The primary processes of charge separation and catalysis, which occur in the natural photosynthetic machinery, provide us with an excellent blueprint for the design of such systems. This Account describes our efforts to construct supramolecular assemblies capable of carrying out photoinduced electron transfer and to develop artificial water oxidation catalysts (WOCs). Early work in our group focused on linking a ruthenium chromophore to a manganese-based oxidation catalyst. When we incorporated a tyrosine unit into these supramolecular assemblies, we could observe fast intramolecular electron transfer from the manganese centers, via the tyrosine moiety, to the photooxidized ruthenium center, which clearly resembles the processes occurring in the natural system. Although we demonstrated multi-electron transfer in our artificial systems, the bottleneck proved to be the stability of the WOCs. Researchers have developed a number of WOCs, but the majority can only catalyze H2O oxidation in the presence of strong oxidants such as Ce-IV, which is difficult to generate photochemically. By contrast, illumination of ruthenium(II) photosensitizers in the presence of a sacrificial acceptor generates [Ru(bpy)(3)](3+)-type oxidants. Their oxidation potentials are significantly lower than that of Ce-IV, but our group recently showed that incorporating negatively charged groups into the ligand backbone could decrease the oxidation potential of the catalysts and, at the same time, decrease the potential for H2O oxidation. This permitted us to develop both ruthenium- and manganese-based WOCs that can operate under neutral conditions, driven by the mild oxidant [Ru(bpy)(3)](3+). Many hurdles to the development of viable systems for the production of solar fuels remain. However, the combination of important features from the natural photosynthetic machinery and novel artificial components adds insights into the complicated catalytic processes that are involved in splitting H2O.

  • 23.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Molecular Single-site Ruthenium Complexes Containing a Basic Site: The Use of Structure-activity RelationshipsManuscript (preprint) (Other academic)
    Abstract [en]

    A series of single-site ruthenium(III) complexes (2a-d) were synthesized and characterized, and employed in the oxidation of H2O. A linear free-energy relationship study was conducted in order to establish a correlation between the electrochemical properties and the electronic parameters of the introduced substituents in complexes 2a-d.

  • 24.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Li, Ying-Ying
    Huazhong Univ Sci & Technol, Sch Chem & Chem Engn, Key Lab Mat Chem Energy Convers & Storage, Hubei Key Lab Mat Chem & Serv Failure,Minist Educ, Wuhan 430074, Hubei, Peoples R China..
    Siegbahn, Per E. M.
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Liao, Rong-Zhen
    Huazhong Univ Sci & Technol, Sch Chem & Chem Engn, Key Lab Mat Chem Energy Convers & Storage, Hubei Key Lab Mat Chem & Serv Failure,Minist Educ, Wuhan 430074, Hubei, Peoples R China..
    Åkermark, Björn
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Metal-Ligand Cooperation in Single-Site Ruthenium Water Oxidation Catalysts: A Combined Experimental and Quantum Chemical Approach2018In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 17, p. 10881-10895Article in journal (Refereed)
    Abstract [en]

    Catalysts for oxidation of water to molecular oxygen are essential in solar-driven water splitting. In order to develop more efficient catalysts for this oxidatively demanding reaction, it is vital to have mechanistic insight in order to understand how the catalysts operate. Herein, we report the mechanistic details associated with the two Ru catalysts 1 and 2. Insight into the mechanistic landscape of water oxidation catalyzed by the two single-site Ru catalysts was revealed by the use of a combination of experimental techniques and quantum chemical calculations. On the basis of the obtained results, detailed mechanisms for oxidation of water by complexes 1 and 2 are proposed. Although the two complexes are structurally related, two deviating mechanistic scenarios are proposed with metal-ligand cooperation being an important feature in both processes. The proposed mechanistic platforms provide insight for the activation of water or related small molecules through nontraditional and previously unexplored routes.

  • 25. Kärkäs, Markus D.
    et al.
    Li, Ying-Ying
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Metal-Ligand Cooperation in Single-Site Ruthenium Water Oxidation Catalysts: A Combined Experimental and Quantum Chemical Approach2018In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 17, p. 10881-10895Article in journal (Refereed)
    Abstract [en]

    Catalysts for oxidation of water to molecular oxygen are essential in solar-driven water splitting. In order to develop more efficient catalysts for this oxidatively demanding reaction, it is vital to have mechanistic insight in order to understand how the catalysts operate. Herein, we report the mechanistic details associated with the two Ru catalysts 1 and 2. Insight into the mechanistic landscape of water oxidation catalyzed by the two single-site Ru catalysts was revealed by the use of a combination of experimental techniques and quantum chemical calculations. On the basis of the obtained results, detailed mechanisms for oxidation of water by complexes 1 and 2 are proposed. Although the two complexes are structurally related, two deviating mechanistic scenarios are proposed with metal-ligand cooperation being an important feature in both processes. The proposed mechanistic platforms provide insight for the activation of water or related small molecules through nontraditional and previously unexplored routes.

  • 26.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ghanem, Shams
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Molecular ruthenium water oxidation catalysts carrying non-innocent ligands: mechanistic insight through structure-activity relationships and quantum chemical calculations2016In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 6, no 5, p. 1306-1319Article in journal (Refereed)
    Abstract [en]

    Robust catalysts that mediate H2O oxidation are of fundamental importance for the development of novel carbon-neutral energy technologies. Herein we report the synthesis of a group of single-site Ru complexes. Structure-activity studies revealed that the individual steps in the oxidation of H2O depended differently on the electronic properties of the introduced ligand substituents. The mechanistic details associated with these complexes were investigated experimentally along with quantum chemical calculations. It was found that O-O bond formation for the developed Ru complexes proceeds via high-valent Ru-VI species, where the capability of accessing this species is derived from the non-innocent ligand architecture. This cooperative catalytic involvement and the ability of accessing Ru-VI are intriguing and distinguish these Ru catalysts from a majority of previously reported complexes, and might generate unexplored reaction pathways for activation of small molecules such as H2O.

  • 27.
    Kärkäs, Markus D.
    et al.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Matsuura, Bryan S.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Monos, Timothy M.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Magallanes, Gabriel
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Transition-Metal Catalyzed Valorization of Lignin: The Key to a Sustainable Carbon-Neutral Future2016In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 14, no 6, p. 1853-1914Article, review/survey (Refereed)
    Abstract [en]

    The development of a sustainable, carbon-neutral biorefinery has emerged as a prominent scientific and engineering goal of the 21st century. As petroleum has become less accessible, biomass-based carbon sources have been investigated for utility in fuel production and commodity chemical manufacturing. One underutilized biomaterial is lignin; however, its highly crosslinked and randomly polymerized composition have rendered this biopolymer recalcitrant to existing chemical processing. More recently, insight into lignin's molecular structure has reinvigorated chemists to develop catalytic methods for lignin depolymerization. This review examines the development of transition-metal catalyzed reactions and the insights shared between the homogeneous and heterogeneous catalytic systems towards the ultimate goal of valorizing lignin to produce value-added products.

  • 28.
    Kärkäs, Markus D.
    et al.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Matsuura, Bryan S.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Enchained by Visible Light–Mediated Photoredox Catalysis2015In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 349, no 6254, p. 1285-1286Article in journal (Refereed)
    Abstract [en]

    Free radicals are exploited in biology, often through highly controlled enzymatic reactions, to drive many reactions that would be difficult via nonradical routes that transfer two electrons (1). In synthetic chemistry, visible-light photoredox catalysis has emerged as an economical and environmentally benign route for promoting free radical transformations in the lab (24). Although the initial light-sensitization steps are well established (5), insufficient attention has been dedicated to essential mechanistic features of the closed catalytic cycle (6). Several reports have hypothesized that these photocatalyzed reactions are terminated through a closed catalytic cycle, which delivers the final product and regenerates the ground state of the photosensitizer (PS). However, Cismesia and Yoon (6) highlight that some of the mechanistic proposals may be incomplete and may involve radical chains.

  • 29.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109, United States.
    Porco, John A. Jr
    Department of Chemistry, Center for Molecular Discovery (BU-CMD), Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.
    Photochemical Approaches to Complex Chemotypes: Applications in Natural Product Synthesis2016In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 116, no 17, p. 9683-9747Article, review/survey (Refereed)
    Abstract [en]

    The use of photochemical transformations is a powerful strategy that allows for the formation of a high degree of molecular complexity from relatively simple building blocks in a single step. A central feature of all light-promoted transformations is the involvement of electronically excited states, generated upon absorption of photons. This produces transient reactive intermediates and significantly alters the reactivity of a chemical compound. The input of energy provided by light thus offers a means to produce strained and unique target compounds that cannot be assembled using thermal protocols. This review aims at highlighting photochemical transformations as a tool for rapidly accessing structurally and stereochemically diverse scaffolds. Synthetic designs based on photochemical transformations have the potential to afford complex polycyclic carbon skeletons with impressive efficiency, which are of high value in total synthesis.

  • 30.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Artificial Photosynthesis: Molecular Systems for Catalytic Water Oxidation2014In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 114, no 24, p. 11863-12001Article, review/survey (Refereed)
  • 31.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Water Oxidation by Ruthenium Complexes Containing Negatively Charged Ligand Frameworks2016In: The chemical record, ISSN 1527-8999, E-ISSN 1528-0691, Vol. 16, no 2, p. 940-963Article in journal (Refereed)
    Abstract [en]

    Artificial photosynthesis represents an attractive way of converting solar energy into storable chemical energy. The H2O oxidation half-reaction, which is essential for producing the necessary reduction equivalents, is an energy-demanding transformation associated with a high kinetic barrier. Herein we present a couple of efficient Ru-based catalysts capable of mediating this four-proton-four-electron oxidation. We have focused on the incorporation of negatively charged ligands, such as carboxylate, phenol, and imidazole, into the catalysts to decrease the redox potentials. This account describes our work in designing Ru catalysts based on this idea. The presence of the negatively charged ligands is crucial for stabilizing the metal centers, allowing for light-driven H2O oxidation. Mechanistic details associated with the designed catalysts are also presented.

  • 32.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water oxidation using earth-abundant transition metal catalysts: opportunities and challenges2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 37, p. 14421-14461Article in journal (Refereed)
    Abstract [en]

    Catalysts for the oxidation of H2O are an integral component of solar energy to fuel conversion technologies. Although catalysts based on scarce and precious metals have been recognized as efficient catalysts for H2O oxidation, catalysts composed of inexpensive and earth-abundant element(s) are essential for realizing economically viable energy conversion technologies. This Perspective summarizes recent advances in the field of designing homogeneous water oxidation catalysts (WOCs) based on Mn, Fe, Co and Cu. It reviews the state of the art catalysts, provides insight into their catalytic mechanisms and discusses future challenges in designing bioinspired catalysts based on earth-abundant metals for the oxidation of H2O.

  • 33.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). China University of Geosciences .
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Tailor-Made Molecular Ruthenium Catalyst for the Oxidation of Water and Its Deactivation through Poisoning by Carbon Monoxide2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 15, p. 4189-4193Article in journal (Refereed)
  • 34.
    Kärkäs, Markus D.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karim, Shams R.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Tobias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Privalov, Timofei
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Water Oxidation by Single-Site Ruthenium Complexes: Using Ligands as Redox and Proton Transfer Mediators2012In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, no 46, p. 11589-11593Article in journal (Refereed)
  • 35.
    Laine, Tanja M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Huazhong University of Science & Technology, People's Republic of China.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A Dinuclear Ruthenium-Based Water Oxidation Catalyst: Use of Non-Innocent Ligand Frameworks for Promoting Multi-Electron Reactions2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 28, p. 10039-10048Article in journal (Refereed)
    Abstract [en]

    Insight into how H2O is oxidized to O-2 is envisioned to facilitate the rational design of artificial water oxidation catalysts, which is a vital component in solar-to-fuel conversion schemes. Herein, we report on the mechanistic features associated with a dinuclear Ru-based water oxidation catalyst. The catalytic action of the designed Ru complex was studied by the combined use of high-resolution mass spectrometry, electrochemistry, and quantum chemical calculations. Based on the obtained results, it is suggested that the designed ligand scaffold in Ru complex 1 has a non-innocent behavior, in which metal-ligand cooperation is an important part during the four-electron oxidation of H2O. This feature is vital for the observed catalytic efficiency and highlights that the preparation of catalysts housing non-innocent molecular frameworks could be a general strategy for accessing efficient catalysts for activation of H2O.

  • 36.
    Laine, Tanja M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Huazhong University of Science & Technology, People's Republic of China.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient photochemical water oxidation by a dinuclear molecular ruthenium complex2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 10, p. 1862-1865Article in journal (Refereed)
    Abstract [en]

    Herein is described the preparation of a dinuclear molecular Ru catalyst for H2O oxidation. The prepared catalyst mediates the photochemical oxidation of H2O with an efficiency comparable to state-of-the-art catalysts.

  • 37.
    Lee, Bao-Lin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Karlsson, Erik A.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnston, Eric
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Das, Biswanath
    Nordlander, Ebbe
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Light-induced water oxidation by a dinuclear iron-based molecular catalystManuscript (preprint) (Other academic)
  • 38.
    Lee, Bao-Lin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Inge, Andrew K.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tran, Lien-Hoa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Xu, Yunhua
    Hansson, Örjan
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis and characterization of oligonuclear Ru, Co, and Cu oxidation catalysts2010In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 34, p. 5462-5470Article in journal (Refereed)
    Abstract [en]

    In this work, we report the preparation and crystal structures of three new oligonuclear complexes, Ru-2(bbpmp)(mu-OAc)(3) (4), [Co-2(bbpmp)(mu-OAc)(mu-OMe)](PF6) (5), [Cu-4(Hbbpmp)(2)(mu-OAc)(H2O)(2)](OAc)(PF6)(2) (6) {H(3)bbpmp = 2,6-bis[(2-hydroxybenzyl)-(2-pyridylmethyl)aminomethyl]-4-methylphenol (3)}. The structures of the complexes were determined by single-crystal X-ray diffraction. The oxidation states of ruthenium, cobalt and copper in the complexes are +3, +3 and +2, respectively. In 4 and 5, Ru-III and Co-III are coordinated to four oxygen and two nitrogen atoms in an octahedral geometry, while in 6, Cu-II adopts both octahedral (CuN2O4) and square-pyramidal (CuN2O3) geometry. The potential of the three complexes as oxidation catalysts has been investigated.

  • 39. Liao, Rong-Zhen
    et al.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Siegbahn, Per E. M.
    On the mechanism of water oxidation catalyzed by a dinuclear ruthenium complex: a quantum chemical study2016In: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 6, no 13, p. 5031-5041Article in journal (Refereed)
    Abstract [en]

    The development of efficient and robust catalysts for H2O oxidation is an essential element in solar water splitting. The reaction mechanism for a previously reported dinuclear Ru water oxidation catalyst (1) has been investigated in detail through quantum chemical calculations. The predicted mechanism starts from a Ru-2(III,III) complex with two aqua ligands. After three sequential oxidations, O-O bond formation occurs at a formal Ru-2(IV,V) state via the direct coupling of two adjacent oxo moieties while the water nucleophilic attack mechanism was found to be associated with a higher energy barrier. Two H2O molecules are then inserted with subsequent release of O-2, which was found to be the rate-limiting step with a barrier of 22.7 kcal mol(-1). In a previous work, it was revealed that the ligand scaffold in the studied Ru complex has a non-innocent function. Here, we further highlight this behavior, where the ligand was shown to mediate proton transfer events and accept/donate electrons during the catalytic cycle, which can significantly decrease the redox potentials and facilitate the access to high-valent redox states. This study provides further insight into the H2O oxidation mechanism and principles for designing improved catalysts for activation of small molecules, such as H2O.

  • 40.
    Liao, Rong-Zhen
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lee, Bao-Lin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Photosystem II Like Water Oxidation Mechanism in a Bioinspired Tetranuclear Manganese Complex2015In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 54, no 1, p. 342-351Article in journal (Refereed)
    Abstract [en]

    The synthesis of Mn-based catalysts to mimic the structural and catalytic properties of the oxygen-evolving complex in photosystem II is a long-standing goal for researchers. An interesting result in this field came with the synthesis of a Mn complex that enables water oxidation driven by the mild single-electron oxidant [Ru(bpy)(3)](3+). On the basis of hybrid density functional calculations, we herein propose a water oxidation mechanism for this bioinspired Mn catalyst, where the crucial O-O bond formation proceeds from the formal Mn-4(IV,IV,IV,V) state by direct coupling of a Mn-IV-bound terminal oxyl radical and a di-Mn bridging oxo group, a mechanism quite similar to the presently leading suggestion for the natural system. Of importance here is that the designed ligand is shown to be redox-active and can therefore store redox equivalents during the catalytic transitions, thereby alleviating the redox processes at the Mn centers.

  • 41.
    Liu, Jian Quan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Mat Sci, Xuzhou 221116, Jiangsu, Peoples R China.
    Chen, Xinyi
    Shatskiy, Andrey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Wang, Xiang-Shan
    Silver-Mediated Synthesis of Substituted Benzofuran- and Indole-Pyrroles via Sequential Reaction of ortho-Alkynylaromatics with Methylene Isocyanides2019In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 84, no 14, p. 8998-9006Article in journal (Refereed)
    Abstract [en]

    A silver-mediated reaction between 2-ethynyl-3-(1-hydroxyprop-2-yn-1-yl)phenols or 2-ethyn-yl-3-(1-hydroxy-prop-2-yn-1-yl)anilines and methylene isocyanides has been developed. A sequential 5-endo-dig cyclization and [3 + 2] cycloaddition process is proposed. This synthetic strategy is atom- and step-efficient and applicable to a broad scope of substrates, allowing the synthesis of valuable substituted benzofuran- and indole-pyrroles in moderate to high yields.

  • 42.
    Liu, Jian-Quan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. KTH Royal Inst Technol, Dept Chem, S-10044 Stockholm, Sweden..
    Shatskiy, Andrey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Matsuura, Bryan S.
    NYU, Dept Chem, New York, NY 10003 USA..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Recent Advances in Photoredox Catalysis Enabled Functionalization of alpha-Amino Acids and Peptides: Concepts, Strategies and Mechanisms2019In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, Vol. 51, no 14, p. 2759-2791Article, review/survey (Refereed)
    Abstract [en]

    The selective modification of alpha-amino acids and peptides constitutes a pivotal arena for accessing new peptide-based materials and therapeutics. In recent years, visible light photoredox catalysis has appeared as a powerful platform for the activation of small molecules via single-electron transfer events, allowing previously inaccessible reaction pathways to be explored. This review outlines the recent advances, mechanistic underpinnings, and opportunities of applying photoredox catalysis to the expansion of the synthetic repertoire for the modification of specific amino acid residues. 1 Introduction 2 Visible-Light-Mediated Functionalization of alpha-Amino Acids 2.1 Decarboxylative Functionalization Involving Redox-Active Esters 2.2 Direct Decarboxylative Coupling Strategies 2.3 Hypervalent Iodine Reagents 2.4 Dual Photoredox and Transition-Metal Catalysis 2.5 Amination and Deamination Strategies 3 Photoinduced Peptide Diversification 3.1 Gese-Type Bioconjugation Methods 3.2 Peptide Macrocyclization through Photoredox Catalysis 3.3 Biomolecule Conjugation through Arylation 3.4 C-H Functionalization Manifolds 4 Conclusions and Outlook

  • 43.
    Liu, Jian-Quan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Chem Engn, Xuzhou 221116, Jiangsu, Peoples R China.
    Shen, Xuanyu
    Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Chem Engn, Xuzhou 221116, Jiangsu, Peoples R China..
    Shatskiy, Andrey
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Zhou, Enlong
    Shandong Agr Univ, Coll Chem & Mat Sci, Tai An 271000, Shandong, Peoples R China..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Wang, Xiang-Shan
    Jiangsu Normal Univ, Jiangsu Key Lab Green Synth Funct Mat, Sch Chem & Chem Engn, Xuzhou 221116, Jiangsu, Peoples R China..
    Silver-Induced [3+2] Cycloaddition of Isocyanides with Acyl Chlorides: Regioselective Synthesis of 2,5-Disubstituted Oxazoles2019In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899Article in journal (Refereed)
    Abstract [en]

    A silver-induced cycloaddition of isocyanides with acyl chlorides has been developed. This transition metal-catalyzed strategy provides an effective and scalable approach for the formation of 2,5-disubstituted oxazoles in good to high yields. The employed silver-based MOF catalyst can be efficiently recycled without compromising the yield.

  • 44.
    Magallanes, Gabriel
    et al.
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Bosque, Irene
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Lee, Sudarat
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Maldonado, Stephen
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA.;Univ Michigan, Program Appl Phys, Ann Arbor, MI 48109 USA..
    Stephenson, Corey R. J.
    Univ Michigan, Dept Chem, Willard Henry Dow Lab, 930 North Univ Ave, Ann Arbor, MI 48109 USA..
    Selective C-O Bond Cleavage of Lignin Systems and Polymers Enabled by Sequential Palladium-Catalyzed Aerobic Oxidation and Visible-Light Photoredox Catalysis2019In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 9, no 3, p. 2252-2260Article in journal (Refereed)
    Abstract [en]

    Lignin, which is a highly cross-linked and irregular biopolymer, is nature's most abundant source of aromatic compounds and constitutes an attractive renewable resource for the production of aromatic commodity chemicals. Herein, we demonstrate a practical and operationally simple two-step degradation approach involving Pd-catalyzed aerobic oxidation and visible-light photoredox-catalyzed reductive fragmentation for the chemoselective cleavage of the beta-O-4 linkage-the predominant linkage in lignin for the generation of lower-molecular-weight aromatic building blocks. The developed strategy affords the beta-O-4 bond cleaved products with high chemoselectivity and in high yields, is amenable to continuous flow processing, operates at ambient temperature and pressure, and is moisture- and oxygen-tolerant.

  • 45.
    Rabten, Wangchuk
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liao, Rong-Zhen
    Tinnis, Fredrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Water Oxidation by a Molecular Ruthenium Complex: Unexpected Generation of a Single-Site Water Oxidation Catalyst2015In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 54, no 10, p. 4611-4620Article in journal (Refereed)
    Abstract [en]

    The increasing energy demand calls for the development of sustainable energy conversion processes. Here, the splitting of H2O to O-2 and H-2, or related fuels, constitutes an excellent example of solar-to-fuel conversion schemes. The critical component in such schemes has proven to be the catalyst responsible for mediating the four-electron oxidation of H2O to O-2. Herein, we report on the unexpected formation of a single-site Ru complex from a ligand envisioned to accommodate two metal centers. Surprising N-N bond cleavage of the designed dinuclear ligand during metal complexation resulted in a single-site Ru complex carrying a carboxylate amide motif. This ligand lowered the redox potential of the Ru complex sufficiently to permit H2O oxidation to be carried out by the mild one-electron oxidant [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine). The work thus highlights that strongly electron-donating ligands are important elements in the design of novel, efficient H2O :oxidation catalysts.

  • 46.
    Rabten, Wangchuk
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Torbjörn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). China University of Geosciences, China.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A ruthenium water oxidation catalyst based on a carboxamide ligand2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 8, p. 3272-3276Article in journal (Refereed)
    Abstract [en]

    Herein is presented a single-site Ru complex bearing a carboxamide-based ligand that efficiently manages to carry out the fourelectron oxidation of H2O. The incorporation of the negatively charged ligand framework significantly lowered the redox potentials of the Ru complex, allowing H2O oxidation to be driven by the mild oxidant [Ru(bpy)(3)](3+). This work highlights that the inclusion of amide moieties into metal complexes thus offers access to highly active H2O oxidation catalysts.

  • 47.
    Shatskiy, Andrey
    et al.
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Bardin, Andrey A.
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden.;Russian Acad Sci, Inst Problems Chem Phys, Academician Semenovs Prospect 1g, Moscow 142432, Russia..
    Oschmann, Michael
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Matheu, Roc
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain..
    Benet-Buchholz, Jordi
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain..
    Eriksson, Lars
    Stockholm Univ, Arrhenius Lab, Dept Mat & Environm Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Johnston, Eric, V
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden.;Sigrid Therapeut AB, Sankt Goransgatan 159, S-11217 Stockholm, Sweden..
    Gimbert-Surinach, Carolina
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain..
    Llobet, Antoni
    BIST, Inst Chem Res Catalonia ICIQ, Avinguda Paisos Catalans 16, Tarragona 43007, Spain.;Univ Autonoma Barcelona, Dept Quim, E-08193 Barcelona, Spain..
    Akermark, Bjorn
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, Svante Arrhenius Vag 16C, S-10691 Stockholm, Sweden..
    Electrochemically Driven Water Oxidation by a Highly Active Ruthenium-Based Catalyst2019In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 12, no 10, p. 2251-2262Article in journal (Refereed)
    Abstract [en]

    The highly active ruthenium-based water oxidation catalyst [Ru-X(mcbp)(OHn)(py)(2)] [mcbp(2-)=2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine; n=2, 1, and 0 for X=II, III, and IV, respectively], can be generated in a mixture of Ru-III and Ru-IV states from either [Ru-II(mcbp)(py)(2)] or [Ru-III(Hmcbp)(py)(2)](2+) precursors. The precursor complexes are isolated and characterized by single-crystal X-ray analysis, NMR, UV/Vis, EPR, and FTIR spectroscopy, ESI-HRMS, and elemental analysis, and their redox properties are studied in detail by electrochemical and spectroscopic methods. Unlike the parent catalyst [Ru(tda) (py)(2)] (tda(2-)=[2,2:6,2-terpyridine]-6,6-dicarboxylate), for which full transformation into the catalytically active species [Ru-IV(tda)(O)(py)(2)] could not be carried out, stoichiometric generation of the catalytically active Ru-aqua complex [Ru-X(mcbp)(OHn)(py)(2)] from the Ru-II precursor was achieved under mild conditions (pH7.0) and short reaction times. The redox properties of the catalyst were studied and its activity for electrocatalytic water oxidation was evaluated, reaching a maximum turnover frequency (TOFmax) of around 40000s(-1) at pH9.0 (from foot-of-the-wave analysis), which is comparable to the activity of the state-of-the-art catalyst [Ru-IV(tda)(O)(py)(2)].

  • 48.
    Shatskiy, Andrey
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Blomkvist, Björn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Jian-Quan, Liu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Dinér, Peter
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Stereoselective Synthesis of Unnatural α-Amino Acids Through Visible Light-Promoted Decarboxylative C-Radical Addition to a Glyoxylate-Derived Sulfinyl ImineManuscript (preprint) (Other academic)
  • 49.
    Shatskiy, Andrey
    et al.
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, S-10691 Stockholm, Sweden..
    Kärkäs, Markus D.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Åkermark, Björn
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, S-10691 Stockholm, Sweden..
    The Art of Splitting Water: Storing Energy in a Readily Available and Convenient Form2019In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 15, p. 2020-2024Article in journal (Refereed)
    Abstract [en]

    This essay for EurJIC's special issue on "Redox Catalysis for Artificial Photosynthesis" introduces the reader to the field of water oxidation using molecular catalysts. The most essential challenge our society must address during the 21st century is perhaps the realization of a system for producing sustainable energy on the global scale. Currently, there exists an urgent need to develop effective and economical carbon-neutral or carbon-free energy technologies. The production of solar fuels through water splitting constitutes a key enabling element. The construction of robust and efficient catalysts for oxidation of water is therefore essential. In this essay the progress and mechanistic considerations pertaining to molecular water oxidation catalysts are described and discussed from a personal perspective.

  • 50.
    Shatskiy, Andrey
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lomoth, Reiner
    Abdel-Magied, Ahmed F.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Nuclear Materials Authority, Egypt.
    Rabten, Wangchuk
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chen, Hong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH Royal Institute of Technology, Sweden.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Andersson, Pher G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalyst-solvent interactions in a dinuclear Ru-based water oxidation catalyst2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 47, p. 19024-19033Article in journal (Refereed)
    Abstract [en]

    Photocatalytic water oxidation represents a key process in conversion of solar energy into fuels and can be facilitated by the use of molecular transition metal-based catalysts. A novel straightforward approach for covalent linking of the catalytic units to other moieties is demonstrated by preparation of a dinuclear complex containing two [Ru(pdc)(pic)(3)]-derived units (pdc = 2,6-pyridinedicarboxylate, pic = 4-picoline). The activity of this complex towards chemical and photochemical oxidation of water was evaluated and a detailed insight is given into the interactions between the catalyst and acetonitrile, a common co-solvent employed to increase solubility of water oxidation catalysts. The solvent-induced transformations were studied by electrochemical and spectroscopic techniques and the relevant quantitative parameters were extracted.

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