Publications by authors named "Nicole Orth"

13 Publications

  • Page 1 of 1

Redox-Induced Hydrogen Bond Reorientation Mimicking Electronic Coupling in Mixed-Valent Diruthenium and Macrocyclic Tetraruthenium Complexes.

Inorg Chem 2020 Nov 2;59(22):16703-16715. Epub 2020 Nov 2.

Fachbereich Chemie, Universität Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany.

We present the coordination-driven self-assembly of three tetranuclear metallacycles containing intracyclic NH, OH, or OMe functionalities through the combination of various isophthalic acid building blocks with a divinylphenylene diruthenium complex. All new complexes of this study were characterized by means of nuclear magnetic resonance spectroscopy, ultrahigh-resolution ESI mass spectrometry, cyclic and square wave voltammetry and, in two cases, X-ray diffraction. The hydroxy functionalized macrocycle and the corresponding half-cycle stand out, as their intracyclic OHO hydrogen bonds stabilize their mixed-valent one- (, ) and three-electron-oxidized states (). Despite sizable redox splittings between all one-electron waves, the mixed-valent monocations and trications do not exhibit any intervalence charge-transfer band, assignable to through-bond electronic coupling, but nevertheless display distinct IR band shifts of their charge-sensitive Ru(CO) tags. We ascribe these seemingly contradicting observations to a redox-induced shuffling of the OHO hydrogen bond(s) to the remaining, more electron-rich, reduced redox site.
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http://dx.doi.org/10.1021/acs.inorgchem.0c02695DOI Listing
November 2020

Catalytic HO Activation by a Diiron Complex for Methanol Oxidation.

Inorg Chem 2020 Nov 21;59(21):15563-15569. Epub 2020 Oct 21.

Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany.

In nature, C-H bond oxidation of CH involves a peroxo intermediate that decays to the high-valent active species of either a "closed" {Fe(μ-O)Fe} core or an "open" {Fe(O)(μ-O)Fe(O)} core. To mimic and to obtain more mechanistic insight in this reaction mode, we have investigated the reactivity of the bioinspired diiron complex [(susan){Fe(OH)(μ-O)Fe(OH)}] [susan = 4,7-dimethyl-1,1,10,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraazadecane], which catalyzes CHOH oxidation with HO to HCHO and HCOH. The kinetics is faster in the presence of a proton. O-labeling experiments show that the active species, generated by a decay of the initially formed peroxo intermediate [(susan){Fe(μ-O)(μ-O)Fe}], contains one reactive oxygen atom from the μ-oxo and another from the μ-peroxo bridge of its peroxo precursor. Considering an FeFe active species, a "closed" {Fe(μ-O)Fe} core explains the observed labeling results, while a scrambling of the terminal and bridging oxo ligands is required to account for an "open" {Fe(O)(μ-O)Fe(O)} core.
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http://dx.doi.org/10.1021/acs.inorgchem.0c02698DOI Listing
November 2020

Hydrogenase Mimics in M L Nanospheres to Control Overpotential and Activity in Proton-Reduction Catalysis.

Angew Chem Int Ed Engl 2020 10 17;59(42):18485-18489. Epub 2020 Aug 17.

Homogeneous, Supramolecular and Bio-Inspired Catalysis, van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.

Hydrogenase enzymes are excellent proton reduction catalysts and therefore provide clear blueprints for the development of nature-inspired synthetic analogues. Mimicking their catalytic center is straightforward but mimicking the protein matrix around the active site and all its functions remains challenging. Synthetic models lack this precisely controlled second coordination sphere that provides substrate preorganization and catalyst stability and, as a result, their performances are far from those of the natural enzyme. In this contribution, we report a strategy to easily introduce a specific yet customizable second coordination sphere around synthetic hydrogenase models by encapsulation inside M L cages and, at the same time, create a proton-rich nano-environment by co-encapsulation of ammonium salts, effectively providing substrate preorganization and intermediates stabilization. We show that catalyst encapsulation in these nanocages reduces the catalytic overpotential for proton reduction by 250 mV as compared to the uncaged catalyst, while the proton-rich nano-environment created around the catalyst ensures that high catalytic rates are maintained.
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http://dx.doi.org/10.1002/anie.202008298DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589440PMC
October 2020

Ring size matters: supramolecular isomerism in self-assembled redox-active tetra- and hexaruthenium macrocycles.

Chem Commun (Camb) 2020 Jan 24;56(7):1062-1065. Epub 2019 Dec 24.

Fachbereich Chemie, Universität Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany.

Self-assembly of a divinylthiophene-bridged diruthenium complex with 2,5-furandicarboxylate leads to the formation of two macrocyclic structures that differ solely with regard to their respective nuclearities. Both supramolecular isomers were fully characterized and the conversion of the hexa- to the tetraruthenium macrocycle was followed by NMR monitoring.
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http://dx.doi.org/10.1039/c9cc09307aDOI Listing
January 2020

Reversible multi-electron storage in dual-site redox-active supramolecular cages.

Chem Commun (Camb) 2019 Oct;55(84):12619-12622

van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, Amsterdam, The Netherlands.

M6L412+ supramolecular cages 3a and 3b (M = Pd, Pt), soluble in organic solvents, contain two different ligand-centered redox sites that enable the reversible storage of up to 16 electrons, as probed by CV, UV/vis spectro-electrochemistry (SEC-UV/Vis), bulk electrolysis and EPR. Encapsulation of a B12F122- anion is confirmed by 1H, 19F NMR and 19F DOSY NMR spectroscopy and mass spectrometry.
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http://dx.doi.org/10.1039/c9cc07138eDOI Listing
October 2019

Dual oxidase/oxygenase reactivity and resonance Raman spectra of {CuO} moiety with perfluoro-t-butoxide ligands.

Dalton Trans 2019 May;48(20):6899-6909

Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, USA.

A Cu(i) fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2], was previously shown to form a trinuclear copper-dioxygen species with a {Cu3(μ3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. Herein is reported a significantly expanded kinetic and mechanistic study of TOC4F9 formation using stopped-flow spectroscopy. The TOC4F9 complex performs catalytic oxidase conversion of hydroquinone (H2Q) to benzoquinone (Q). TOC4F9 also demonstrated hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first trinuclear species to perform tyrosinase (both monooxygenase and oxidase) chemistry. Resonance Raman spectra were also obtained for TOC4F9, to our knowledge, the first such spectra for any T species. The mechanism and substrate reactivity of TOC4F9 are compared to those of its bidentate counterpart, TpinF, formed from K[Cu(pinF)(PR3)]. The monodentate derivative has both faster initial formation and more diverse substrate reactivity.
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http://dx.doi.org/10.1039/c9dt00516aDOI Listing
May 2019

Self-assembled ML nanospheres as a reaction vessel to facilitate a dinuclear Cu(i) catalyzed cyclization reaction.

Chem Sci 2019 Feb 13;10(5):1316-1321. Epub 2018 Nov 13.

Homogeneous, Supramolecular and Bio-Inspired Catalysis , Van 't Hoff Institute for Molecular Sciences , University of Amsterdam , Science Park 904 , Amsterdam 1098XH , The Netherlands . Email:

The application of large ML nanospheres allows the pre-concentration of catalysts to reach high local concentrations, facilitating reactions that proceed through dinuclear mechanisms. The mechanism of the copper(i)-catalyzed cyclization of 4-pentynoic acid has been elucidated by means of a detailed mechanistic study. The kinetics of the reaction show a higher order in copper, indicating the formation of a bis-Cu intermediate as the key rate determining step of the reaction. This intermediate was further identified during catalysis by CIS-HRMS analysis of the reaction mixture. Based on the mechanistic findings, an ML nanosphere was applied that can bind up to 12 copper catalysts by hydrogen bonding. This pre-organization of copper catalysts in the nanosphere results in a high local concentration of copper leading to higher reaction rates and turnover numbers as the dinuclear pathway is favored.
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http://dx.doi.org/10.1039/c8sc03767aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6354833PMC
February 2019

A Fluorescent Benzo[g]isoquinoline-Based HIF Prolyl Hydroxylase Inhibitor for Cellular Imaging.

ChemMedChem 2019 01 21;14(1):94-99. Epub 2018 Dec 21.

Department of Chemistry and Pharmacy, Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058, Erlangen, Germany.

Prolyl hydroxylation domain (PHD) enzymes catalyze the hydroxylation of the transcription factor hypoxia-inducible factor (HIF) and serve as cellular oxygen sensors. HIF and the PHD enzymes regulate numerous potentially tissue-protective target genes which can adapt cells to metabolic and ischemic stress. We describe a fluorescent PHD inhibitor (1-chloro-4-hydroxybenzo[g]isoquinoline-3-carbonyl)glycine which is suited to fluorescence-based detection assays and for monitoring PHD inhibitors in biological systems. In cell-based assays, application of the fluorescent PHD inhibitor allowed co-localization with a cellular PHD enzyme and led to live cell imaging of processes involved in cellular oxygen sensing.
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http://dx.doi.org/10.1002/cmdc.201800483DOI Listing
January 2019

An Isolable Terminal Imido Complex of Palladium and Catalytic Implications.

Angew Chem Int Ed Engl 2018 Dec 8;57(49):16228-16232. Epub 2018 Nov 8.

Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 1, 91058, Erlangen, Germany.

Herein, we report the isolation and a reactivity study of the first example of an elusive palladium(II) terminal imido complex. This scaffold is an alleged key intermediate for various catalytic processes, including the amination of C-H bonds. We demonstrate facile nitrene transfer with H-H, C-H, N-H, and O-H bonds and elucidate its role in catalysis. The high reactivity is due to the population of the antibonding highest occupied molecular orbital (HOMO), which results in unique charge separation within the closed-shell imido functionality. Hence, N atom transfer is not necessarily associated with the high valency of the metal (Pd , Pd ) or the open-shell character of a nitrene as commonly inferred.
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http://dx.doi.org/10.1002/anie.201809152DOI Listing
December 2018

Two Unsupported Terminal Hydroxido Ligands in a μ-Oxo-Bridged Ferric Dimer: Protonation and Kinetic Lability Studies.

Inorg Chem 2018 Aug 31;57(16):10457-10468. Epub 2018 Jul 31.

Fakultät für Chemie , Universität Bielefeld , Universitätsstrasse 25 , D-33615 Bielefeld , Germany.

The dinuclear complex [(susan){Fe(OH)(μ-O)Fe(OH)}](ClO) (Fe(OH)(ClO); susan = 4,7-dimethyl-1,1,10,10-tetra(2-pyridylmethyl)-1,4,7,10-tetraazadecane) with two unsupported terminal hydroxido ligands and for comparison the fluorido-substituted complex [(susan){FeF(μ-O)FeF}](ClO) (FeF(ClO)) have been synthesized and characterized in the solid state as well in acetonitrile (CHCN) and water (HO) solutions. The Fe-OH bonds are strongly modulated by intermolecular hydrogen bonds (1.85 and 1.90 Å). UV-vis-near-IR (NIR) and Mössbauer spectroscopies prove that FeF and Fe(OH) retain their structural integrity in a CHCN solution. The OH ligand induces a weaker ligand field than the F ligand because of stronger π donation. This increased electron donation shifts the potential for the irreversible oxidation by 610 mV cathodically from 1.40 V in FeF to 0.79 V versus Fc/Fc in Fe(OH). Protonation/deprotonation studies in CHCN and aqueous solutions of Fe(OH) provide two reversible acid-base equilibria. UV-vis-NIR, Mössbauer, and cryo electrospray ionization mass spectrometry experiments show conservation of the mono(μ-oxo) bridging motif, while the terminal OH ligands are protonated to HO. Titration experiments in aqueous solution at room temperature provide the p K values as p K = 4.9 and p K = 6.8. Kinetic studies by temperature- and pressure-dependent O NMR spectrometry revealed for the first time the water-exchange parameters [ k = (3.9 ± 0.2) × 10 s, Δ H = 39.6 ± 0.2 kJ mol, Δ S = -5.1 ± 1 J mol K, and Δ V = +3.0 ± 0.2 cm mol] and the underlying I mechanism for a {Fe(OH)(μ-O)Fe(OH)} core. The same studies suggest that in solution the monoprotonated {Fe(OH)(μ-O)Fe(OH)} complex has μ-O and μ-OH bridges between the two Fe centers.
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http://dx.doi.org/10.1021/acs.inorgchem.8b01831DOI Listing
August 2018

Control over Electrochemical Water Oxidation Catalysis by Preorganization of Molecular Ruthenium Catalysts in Self-Assembled Nanospheres.

Angew Chem Int Ed Engl 2018 Aug 1;57(35):11247-11251. Epub 2018 Aug 1.

Homogeneous, Supramolecular and Bio-Inspired Catalysis, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098, XH, Amsterdam, The Netherlands.

Oxygen formation through water oxidation catalysis is a key reaction in the context of fuel generation from renewable energies. The number of homogeneous catalysts that catalyze water oxidation at high rate with low overpotential is limited. Ruthenium complexes can be particularly active, especially if they facilitate a dinuclear pathway for oxygen bond formation step. A supramolecular encapsulation strategy is reported that involves preorganization of dilute solutions (10  m) of ruthenium complexes to yield high local catalyst concentrations (up to 0.54 m). The preorganization strategy enhances the water oxidation rate by two-orders of magnitude to 125 s , as it facilitates the diffusion-controlled rate-limiting dinuclear coupling step. Moreover, it modulates reaction rates, enabling comprehensive elucidation of electrocatalytic reaction mechanisms.
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http://dx.doi.org/10.1002/anie.201805244DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120458PMC
August 2018

Designed To React: Terminal Copper Nitrenes and Their Application in Catalytic C-H Aminations.

Angew Chem Int Ed Engl 2018 Jul 19;57(29):9154-9159. Epub 2018 Jun 19.

Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany.

Heteroscorpionate ligands of the bis(pyrazolyl)methane family have been applied in the stabilisation of terminal copper tosyl nitrenes. These species are highly active intermediates in the copper-catalysed direct C-H amination and nitrene transfer. Novel perfluoroalkyl-pyrazolyl- and pyridinyl-containing ligands were synthesized to coordinate to a reactive copper nitrene centre. Four distinct copper tosyl nitrenes were prepared at low temperatures by the reaction with SO tBuPhINTs and copper(I) acetonitrile complexes. Their stoichiometric reactivity has been elucidated regarding the imination of phosphines and the aziridination of styrenes. The formation and thermal decay of the copper nitrenes were investigated by UV/Vis spectroscopy of the highly coloured species. Additionally, the compounds were studied by cryo-UHR-ESI mass spectrometry and DFT calculations. In addition, a mild catalytic procedure has been developed where the copper nitrene precursors enable the C-H amination of cyclohexane and toluene and the aziridination of styrenes.
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http://dx.doi.org/10.1002/anie.201713171DOI Listing
July 2018

On the Way to a Trisanionic {Cu O } Core for Oxidase Catalysis: Evidence of an Asymmetric Trinuclear Precursor Stabilized by Perfluoropinacolate Ligands.

Chemistry 2017 Jun 19;23(34):8212-8224. Epub 2017 Apr 19.

Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, MA, 02215, USA.

Cu complexes of the form K[(R P)Cu(pin )], in which (pin ) is the bidentate, oxygen-donating ligand perfluoropinacolate, were synthesized and characterized. Low-temperature oxygenation of the K[(R P)Cu(pin )(PR )] species resulted in a trisanionic bis(μ -oxo) trinuclear copper(II,II,III) core characterized by UV/Vis spectroscopy (λ [nm] = 330, 535, 630), cryospray-ionization mass spectrometry, and X-band electron paramagnetic resonance spectroscopy (derivative resonance at 3300 G, Δm =2 at 1500 G). The kinetic behavior of the trimeric {Cu O } species was quantified by stopped-flow spectroscopy and the associated electronic structures were investigated by DFT calculations. An asymmetric {Cu O } species, T , which bears a structure similar to multicopper oxidases, forms prior to full formation of the symmetric trinuclear core, T . The trimer catalytically oxidizes para-hydroquinone to benzoquinone (a form of oxidase chemistry).
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http://dx.doi.org/10.1002/chem.201605926DOI Listing
June 2017