@article{56074, abstract = {{Effective photoinduced charge transfer makes molecular bimetallic assemblies attractive for applications as active light‐induced proton reduction systems. Developing competitive base metal dyads is mandatory for a more sustainable future. However, the electron transfer mechanisms from the photosensitizer to the proton reduction catalyst in base metal dyads remain so far unexplored. A Fe─Co dyad that exhibits photocatalytic H2 production activity is studied using femtosecond X‐ray emission spectroscopy, complemented by ultrafast optical spectroscopy and theoretical time‐dependent DFT calculations, to understand the electronic and structural dynamics after photoexcitation and during the subsequent charge transfer process from the Fe(II) photosensitizer to the cobaloxime catalyst. This novel approach enables the simultaneous measurement of the transient X‐ray emission at the iron and cobalt K‐edges in a two‐color experiment. With this methodology, the excited state dynamics are correlated to the electron transfer processes, and evidence of the Fe→Co electron transfer as an initial step of proton reduction activity is unraveled.}}, author = {{Nowakowski, Michał and Huber‐Gedert, Marina and Elgabarty, Hossam and Kalinko, Aleksandr and Kubicki, Jacek and Kertmen, Ahmet and Lindner, Natalia and Khakhulin, Dmitry and Lima, Frederico A. and Choi, Tae‐Kyu and Biednov, Mykola and Schmitz, Lennart and Piergies, Natalia and Zalden, Peter and Kubicek, Katerina and Rodriguez‐Fernandez, Angel and Salem, Mohammad Alaraby and Canton, Sophie E. and Bressler, Christian and Kühne, Thomas D. and Gawelda, Wojciech and Bauer, Matthias}}, issn = {{2198-3844}}, journal = {{Advanced Science}}, keywords = {{Photo, Xray}}, publisher = {{Wiley}}, title = {{{Ultrafast Two‐Color X‐Ray Emission Spectroscopy Reveals Excited State Landscape in a Base Metal Dyad}}}, doi = {{10.1002/advs.202404348}}, year = {{2024}}, } @article{60216, abstract = {{Hydride donors such as DIBAL or CuH react with ZnO and ZrO2 via hydrogen spillover. This suggests that hydrogen spillover in catalysts based on these metal oxides may take place via initial hydride transfer and not via proton–electron transfer.}}, author = {{Benz, Michael and Bunjaku, Osman and Nowakowski, Michał and Allgaier, Alexander and Biswas, Indro and van Slageren, Joris and Bauer, Matthias and Estes, Deven P.}}, issn = {{2044-4753}}, journal = {{Catalysis Science & Technology}}, keywords = {{Xray}}, number = {{20}}, pages = {{5854--5863}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Hydrogen spillover through hydride transfer: the reaction of ZnO and ZrO2 with strong hydride donors}}}, doi = {{10.1039/d4cy00504j}}, volume = {{14}}, year = {{2024}}, } @article{52344, abstract = {{Macrocyclization reactions are still challenging due to competing oligomerization, which requires the use of small substrate concentrations. Here, the cationic tungsten imido and tungsten oxo alkylidene N-heterocyclic carbene complexes [[W(N-2,6-Cl2-C6H3)(CHCMe2Ph(OC6F5)(pivalonitrile)(IMes)+ B(ArF)4−] (W1) and [W(O)(CHCMe2Ph(OCMe(CF3)2)(IMes)(CH3CN)+ B(ArF)4−] (W2) (IMes=1,3-dimesitylimidazol-2-ylidene; B(ArF)4−=tetrakis(3,5-bis(trifluoromethyl)phenyl borate) have been immobilized inside the pores of ordered mesoporous silica (OMS) with pore diameters of 3.3 and 6.8 nm, respectively, using a pore-selective immobilization protocol. X-ray absorption spectroscopy of W1@OMS showed that even though the catalyst structure is contracted due to confinement by the mesopores, both the oxidation state and structure of the catalyst stayed intact upon immobilization. Catalytic testing with four differently sized α,ω-dienes revealed a dramatically increased macrocyclization (MC) and Z-selectivity of the supported catalysts compared to the homogenous progenitors, allowing high substrate concentrations of 25 mM. With the supported complexes, a maximum increase in MC-selectivity from 27 to 81 % and in Z-selectivity from 17 to 34 % was achieved. In general, smaller mesopores exhibited a stronger confinement effect. A comparison of the two supported tungsten-based catalysts showed that W1@OMS possesses a higher MC-selectivity, while W2@OMS exhibits a higher Z-selectivity which can be rationalized by the structures of the catalysts.}}, author = {{Ziegler, Felix and Bruckner, Johanna R. and Nowakowski, Michał and Bauer, Matthias and Probst, Patrick and Atwi, Boshra and Buchmeiser, Michael R.}}, issn = {{1867-3880}}, journal = {{ChemCatChem}}, keywords = {{Inorganic Chemistry, Organic Chemistry, Physical and Theoretical Chemistry, Catalysis}}, number = {{21}}, publisher = {{Wiley}}, title = {{{Macrocyclization of Dienes under Confinement with Cationic Tungsten Imido/Oxo Alkylidene N‐Heterocyclic Carbene Complexes}}}, doi = {{10.1002/cctc.202300871}}, volume = {{15}}, year = {{2023}}, } @article{40981, abstract = {{Room temperature sodium-sulfur (RT Na-S) batteries are considered potential candidates for stationary power storage applications due to their low cost, broad active material availability and low toxicity. Challenges, such as high volume expansion of the S-cathode upon discharge, low electronic conductivity of S as active material and herewith limited rate capability as well as the shuttling of polysulfides (PSs) as intermediates often impede the cycle stability and practical application of Na-S batteries. Sulfurized poly(acrylonitrile) (SPAN) inherently inhibits the shuttling of PSs and shows compatibility with carbonate-based electrolytes, however, its exact redox mechanism remained unclear to date. Herein, we implement a commercially available and simple electrolyte into the Na-SPAN cell chemistry and demonstrate its high rate and cycle stability. Through the application of in situ techniques utilizing electronic impedance spectroscopy (EIS) and X-ray absorption spectroscopy (XAS) at different depths of charge and discharge, an insight into SPAN’s redox chemistry is obtained.}}, author = {{Kappler, Julian and Tonbul, Güldeniz and Schoch, Roland and Murugan, Saravanakumar and Nowakowski, Michał and Lange, Pia Lena and Klostermann, Sina Vanessa and Bauer, Matthias and Schleid, Thomas and Kästner, Johannes and Buchmeiser, Michael Rudolf}}, issn = {{0013-4651}}, journal = {{Journal of The Electrochemical Society}}, keywords = {{Materials Chemistry, Electrochemistry, Surfaces, Coatings and Films, Condensed Matter Physics, Renewable Energy, Sustainability and the Environment, Electronic, Optical and Magnetic Materials}}, number = {{1}}, publisher = {{The Electrochemical Society}}, title = {{{Understanding the Redox Mechanism of Sulfurized Poly(acrylonitrile) as Highly Rate and Cycle Stable Cathode Material for Sodium-Sulfur Batteries}}}, doi = {{10.1149/1945-7111/acb2fa}}, volume = {{170}}, year = {{2023}}, } @unpublished{40982, abstract = {{Effective photoinduced charge transfer makes molecular bimetallic assemblies attractive for applications as active light induced proton reduction systems. For a more sustainable future, development of competitive base metal dyads is mandatory. However, the electron transfer mechanisms from the photosensitizer to the proton reduction catalyst in base metal dyads remain so far unexplored. We study a Fe-Co dyad that exhibits photocatalytic H2 production activity using femtosecond X-ray emission spectroscopy, complemented by ultrafast optical spectroscopy and theoretical time-dependent DFT calculations, to understand the electronic and structural dynamics after photoexcitation and during the subsequent charge transfer process from the FeII photosensitizer to the cobaloxime catalyst. Using this novel approach, the simultaneous measurement of the transient Kalpha X-ray emission at the iron and cobalt K-edges in a two-colour experiment is enabled making it possible to correlate the excited state dynamics to the electron transfer processes. The methodology, therefore, provides a clear and direct spectroscopic evidence of the Fe->Co electron transfer responsible for the proton reduction activity.}}, author = {{Nowakowski, Michał and Huber-Gedert, Marina and Elgabarty, Hossam and Kubicki, Jacek and Kertem, Ahmet and Lindner, Natalia and Khakhulin, Dimitry and Lima, Frederico Alves and Choi, Tae-Kyu and Biednov, Mykola and Piergies, Natalia and Zalden, Peter and Kubicek, Katerina and Rodriguez-Fernandez, Angel and Salem, Mohammad Alaraby and Kühne, Thomas and Gawelda, Wojciech and Bauer, Matthias}}, booktitle = {{arxiv}}, title = {{{Ultrafast two-colour X-ray emission spectroscopy reveals excited state landscape in a base metal dyad}}}, year = {{2023}}, } @inproceedings{47316, author = {{Nowakowski, Michał and Berndt, Axel and Plaksin, Anna Viktoria Katrin and Şahin, N. and Hadjakos, A.}}, booktitle = {{{Encoding Cultures—Joint MEC and TEI Conference 2023}}}, title = {{{Mixing Modalities: Graphical and Text-Based Interaction in Music Notation Editing}}}, year = {{2023}}, } @inproceedings{47322, author = {{Nowakowski, Michał and Berndt, Axel and Hadjakos, A.}}, booktitle = {{{Digital Humanities im deutschsprachigen Raum (DHd): Open Humanities, Open Culture}}}, title = {{{Forschungsperspektiven zur Interaktion mit Musiknotation}}}, year = {{2023}}, } @inproceedings{50434, author = {{Nowakowski, Michał and Berndt, Axel and Plaksin, Anna Viktoria Katrin and Şahin, N. and Hadjakos, A.}}, booktitle = {{{Encoding Cultures—Joint MEC and TEI Conference 2023}}}, title = {{{Mixing Modalities: Graphical and Text-Based Interaction in Music Notation Editing}}}, year = {{2023}}, } @article{48167, abstract = {{AbstractA new approach for the characterization of CO2 methanation catalysts prepared by thermal decomposition of a nickel MOF by hard X‐ray photon‐in/photon‐out spectroscopy in form of high energy resolution fluorescence detected X‐ray absorption near edge structure spectroscopy (HERFD‐XANES) and valence‐to‐core X‐ray emission (VtC‐XES) is presented. In contrast to conventional X‐ray absorption spectroscopy, the increased resolution of both methods allows a more precise phase determination of the final catalyst, which is influenced by the conditions during MOF decomposition.}}, author = {{Strübbe, Sven and Nowakowski, Michał and Schoch, Roland and Bauer, Matthias}}, issn = {{1439-4235}}, journal = {{ChemPhysChem}}, keywords = {{Catalysis}}, publisher = {{Wiley}}, title = {{{High‐Resolution X‐ray Absorption and Emission Spectroscopy for Detailed Analysis of New CO2 Methanation Catalysts}}}, doi = {{10.1002/cphc.202300113}}, year = {{2023}}, } @article{40986, abstract = {{Currently, chemistry and physics are strongly dependent on the concept of the oxidation state. While the formal oxidation state is easily evaluated, the real physical oxidation state value is often difficult to determine and significantly varies from the formal values. Determination of the ionization threshold in X-ray absorption spectroscopy (XANES) relies on the absorption edge position and sometimes poses limitations, mainly due to the edge resonances. Moreover, the lower energy states can be probed only within x-soft or XUV photons providing only surface state information of probed materials. Here, we employ high energy resolution off-resonant spectroscopy to determine both 1s and 3p binding energies of Fe-based materials and therefore correlate to their physical oxidation state. The results are compared to the ones obtained with classical X-ray absorption, X-ray emission, and photoelectron spectroscopies. The observed differences in binding energies are discussed in a frame of initial and final state interactions with the atom's electronic configurations. The presented methodology is discussed towards potential use to single-shot experiments and application at X-ray free-electron lasers. Alternatively, core level X-ray emission spectroscopy can be used, but the emission line positions are strongly affected by spin-orbit interaction. However, due to the energy transfer from the photon to the excited core electron, the same information as in XANES is probed in high energy resolution off-resonant spectroscopy (HEROS). Based on the Kramers–Heisenberg theory, we propose a new approach for ionization threshold determination which is free of the limitations encountered in XANES-based determination of the core state energy. Namely, the value of core state energy can be determined analytically using a few HEROS spectra recorded with significantly higher spectral resolution. This approach provides a basis for the universal physical oxidation state determination method.}}, author = {{Nowakowski, Michał and Kalinko, Aleksandr and Szlachetko, Jakub and Fanselow, Rafał and Bauer, Matthias}}, issn = {{0267-9477}}, journal = {{Journal of Analytical Atomic Spectrometry}}, keywords = {{Spectroscopy, Analytical Chemistry}}, number = {{11}}, pages = {{2383--2391}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{High resolution off resonant spectroscopy as a probe of the oxidation state}}}, doi = {{10.1039/d2ja00232a}}, volume = {{37}}, year = {{2022}}, } @article{41001, abstract = {{For entropic reasons, the synthesis of macrocycles via olefin ring-closing metathesis (RCM) is impeded by competing acyclic diene metathesis (ADMET) oligomerization. With cationic molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes confined in tailored ordered mesoporous silica, RCM can be run with macrocyclization selectivities up to 98% and high substrate concentrations up to 0.1 M. Molecular dynamics simulations show that the high conversions are a direct result of the proximity between the surface-bound catalyst, proven by extended X-ray absorption spectroscopy, and the surface-located substrates. Back-diffusion of the macrocycles decreases with decreasing pore diameter of the silica and is responsible for the high macrocyclization efficiency. Also, Z-selectivity increases with decreasing pore diameter and increasing Tolman electronic parameter of the NHC. Running reactions at different concentrations allows for identifying the optimum substrate concentration for each material and substrate combination.}}, author = {{Ziegler, Felix and Kraus, Hamzeh and Benedikter, Mathis J. and Wang, Dongren and Bruckner, Johanna R. and Nowakowski, Michał and Weißer, Kilian and Solodenko, Helena and Schmitz, Guido and Bauer, Matthias and Hansen, Niels and Buchmeiser, Michael R.}}, issn = {{2155-5435}}, journal = {{ACS Catalysis}}, keywords = {{Catalysis, General Chemistry}}, number = {{18}}, pages = {{11570--11578}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Confinement Effects for Efficient Macrocyclization Reactions with Supported Cationic Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes}}}, doi = {{10.1021/acscatal.1c03057}}, volume = {{11}}, year = {{2021}}, } @article{40999, abstract = {{Rh(I) NHC and Rh(III) Cp* NHC complexes (Cp*=pentamethylcyclopentadienyl, NHC=N-heterocyclic carbene=pyrid-2-ylimidazol-2-ylidene (Py−Im), thiophen-2-ylimidazol-2-ylidene) are presented. Selected catalysts were selectively immobilized inside the mesopores of SBA-15 with average pore diameters of 5.0 and 6.2 nm. Together with their homogenous progenitors, the immobilized catalysts were used in the hydrosilylation of terminal alkynes. For aromatic alkynes, both the neutral and cationic Rh(I) complexes showed excellent reactivity with exclusive formation of the β(E)-isomer. For aliphatic alkynes, however, selectivity of the Rh(I) complexes was low. By contrast, the neutral and cationic Rh(III) Cp* NHC complexes proved to be highly regio- and stereoselective catalysts, allowing for the formation of the thermodynamically less stable β-(Z)-vinylsilane isomers at room temperature. Notably, the SBA-15 immobilized Rh(I) catalysts, in which the pore walls provide an additional confinement, showed excellent β-(Z)-selectivity in the hydrosilylation of aliphatic alkynes, too. Also, in the case of 4-aminophenylacetylene, selective formation of the β(Z)-isomer was observed with a neutral SBA-15 supported Rh(III) Cp* NHC complex but not with its homogenous counterpart. These are the first examples of high β(Z)-selectivity in the hydrosilylation of alkynes by confinement generated upon immobilization inside mesoporous silica.}}, author = {{Panyam, Pradeep K. R. and Atwi, Boshra and Ziegler, Felix and Frey, Wolfgang and Nowakowski, Michał and Bauer, Matthias and Buchmeiser, Michael R.}}, issn = {{0947-6539}}, journal = {{Chemistry – A European Journal}}, keywords = {{General Chemistry, Catalysis, Organic Chemistry}}, number = {{68}}, pages = {{17220--17229}}, publisher = {{Wiley}}, title = {{{Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes}}}, doi = {{10.1002/chem.202103099}}, volume = {{27}}, year = {{2021}}, } @article{41009, abstract = {{Platinum hydride species catalyze a number of interesting organic reactions. However, their reactions typically involve the use of high loadings of noble metal and are difficult to recycle, making them somewhat unsustainable. We have synthesized surface-immobilized Pt–H species via oxidative addition of surface OH groups to Pt(PtBu3)2 (1), a rarely used immobilization technique in surface organometallic chemistry. The hydride species thus made were characterized by infrared, magic-angle spinning nuclear magnetic resonance, and X-ray absorption spectroscopies and catalyzed both olefin isomerization and cycloisomerization of a 1,6 enyne (5) with a high selectivity and low Pt loading.}}, author = {{Maier, Sarah and Cronin, Steve P. and Vu Dinh, Manh-Anh and Li, Zheng and Dyballa, Michael and Nowakowski, Michał and Bauer, Matthias and Estes, Deven P.}}, issn = {{0276-7333}}, journal = {{Organometallics}}, keywords = {{Inorganic Chemistry, Organic Chemistry, Physical and Theoretical Chemistry}}, number = {{11}}, pages = {{1751--1757}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Immobilized Platinum Hydride Species as Catalysts for Olefin Isomerizations and Enyne Cycloisomerizations}}}, doi = {{10.1021/acs.organomet.1c00216}}, volume = {{40}}, year = {{2021}}, } @article{30216, author = {{Huber-Gedert, Marina and Nowakowski, Michał and Kertmen, Ahmet and Burkhardt, Lukas and Lindner, Natalia and Schoch, Roland and Herbst‐Irmer, Regine and Neuba, Adam and Schmitz, Lennart and Choi, Tae‐Kyu and Kubicki, Jacek and Gawelda, Wojciech and Bauer, Matthias}}, issn = {{0947-6539}}, journal = {{Chemistry – A European Journal}}, keywords = {{Photocatalytic Hydrogen Production, Catalysis, Inorganic Chemistry}}, number = {{38}}, pages = {{9905--9918}}, publisher = {{Wiley}}, title = {{{Fundamental Characterization, Photophysics and Photocatalysis of a Base Metal Iron(II)‐Cobalt(III) Dyad}}}, doi = {{10.1002/chem.202100766}}, volume = {{27}}, year = {{2021}}, } @article{41022, author = {{Kirchhof, Manuel and Gugeler, Katrin and Fischer, Felix Richard and Nowakowski, Michał and Bauer, Alina and Alvarez-Barcia, Sonia and Abitaev, Karina and Schnierle, Marc and Qawasmi, Yaseen and Frey, Wolfgang and Baro, Angelika and Estes, Deven P. and Sottmann, Thomas and Ringenberg, Mark R. and Plietker, Bernd and Bauer, Matthias and Kästner, Johannes and Laschat, Sabine}}, issn = {{0276-7333}}, journal = {{Organometallics}}, keywords = {{Inorganic Chemistry, Organic Chemistry, Physical and Theoretical Chemistry}}, number = {{17}}, pages = {{3131--3145}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Experimental and Theoretical Study on the Role of Monomeric vs Dimeric Rhodium Oxazolidinone Norbornadiene Complexes in Catalytic Asymmetric 1,2- and 1,4-Additions}}}, doi = {{10.1021/acs.organomet.0c00310}}, volume = {{39}}, year = {{2020}}, } @article{41015, author = {{Benedikter, Mathis and Musso, Janis and Kesharwani, Manoj K. and Sterz, K. Leonard and Elser, Iris and Ziegler, Felix and Fischer, Felix and Plietker, Bernd and Frey, Wolfgang and Kästner, Johannes and Winkler, Mario and van Slageren, Joris and Nowakowski, Michał and Bauer, Matthias and Buchmeiser, Michael R.}}, issn = {{2155-5435}}, journal = {{ACS Catalysis}}, keywords = {{Catalysis, General Chemistry}}, number = {{24}}, pages = {{14810--14823}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Charge Distribution in Cationic Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes: A Combined X-ray, XAS, XES, DFT, Mössbauer, and Catalysis Approach}}}, doi = {{10.1021/acscatal.0c03978}}, volume = {{10}}, year = {{2020}}, } @article{41020, author = {{Gregori, Bernhard J. and Nowakowski, Michał and Schoch, Anke and Pöllath, Simon and Zweck, Josef and Bauer, Matthias and Jacobi von Wangelin, Axel}}, issn = {{1867-3880}}, journal = {{ChemCatChem}}, keywords = {{Inorganic Chemistry, Organic Chemistry, Physical and Theoretical Chemistry, Catalysis}}, number = {{21}}, pages = {{5359--5363}}, publisher = {{Wiley}}, title = {{{Stereoselective Chromium‐Catalyzed Semi‐Hydrogenation of Alkynes}}}, doi = {{10.1002/cctc.202000994}}, volume = {{12}}, year = {{2020}}, } @article{16311, author = {{Burkhardt, Lukas and Vukadinovic, Yannik and Nowakowski, Michał and Kalinko, Aleksandr and Rudolph, Julian and Carlsson, Per-Anders and Jacob, Christoph R. and Bauer, Matthias}}, issn = {{0020-1669}}, journal = {{Inorganic Chemistry}}, pages = {{3551--3561}}, title = {{{Electronic Structure of the Hieber Anion [Fe(CO)3(NO)]− Revisited by X-ray Emission and Absorption Spectroscopy}}}, doi = {{10.1021/acs.inorgchem.9b02092}}, year = {{2020}}, }