Dr. Matthias Schwalbe

Profil

• Die Aufdeckung des photo-induzierten Assemblierungsmechanismus des lichtgetriebenen Wasseroxidationskomplexes in Photosystem II

  Quelle ↗

  Förderer: DFG Exzellenzinitiative Cluster Zeitraum: 11/2017 - 12/2018 Projektleitung: Prof. Dr. Athina Zouni

• EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  Quelle ↗

  Förderer: DFG Exzellenzstrategie Cluster Zeitraum: 01/2019 - 12/2025 Projektleitung: Prof. Dr. Arne Thomas

• EXC 314/1: Die Aktivierung kleiner Moleküle mit cofacialen heterodinuklearen Metallkatalysatoren des Pacman-Typs (AG Schwalbe)

  Quelle ↗

  Förderer: DFG Exzellenzstrategie Cluster Zeitraum: 01/2019 - 03/2022 Projektleitung: Dr. Matthias Schwalbe

• Hangman-Porphyrin-Verbindungen als biomimetische Modellkomplexe für selektive Oxidationsreaktionen durch die Aktivierung von Wasserstoffperoxid und Sauerstoff

  Quelle ↗

  Förderer: DFG Exzellenzinitiative Cluster Zeitraum: 11/2012 - 10/2017 Projektleitung: Dr. Matthias Schwalbe

• Hetero-Pacman-Verbindungen als potentielle Katalysatoren für die Wasseroxidation, Kohlenstoffdioxid- oder Sauerstoff-Reduktion

  Quelle ↗

  Förderer: DFG Exzellenzinitiative Cluster Zeitraum: 11/2017 - 12/2018 Projektleitung: Dr. Matthias Schwalbe

• Mechanistische Einblicke in die Wirkungsweise von molekularen Katalysatoren während der elektrokatalytischen Reduktion von O2 und CO2

  Quelle ↗

  Förderer: DFG Eigene Stelle (Sachbeihilfe) Zeitraum: 01/2019 - 09/2022 Projektleitung: Dr. Matthias Schwalbe

• Neue multinukleare Metallkatalysatoren zur licht-getriebenen Aktivierung von Wasser und zur Reduktion von CO2

  Quelle ↗

  Förderer: DFG Eigene Stelle (Sachbeihilfe) Zeitraum: 06/2010 - 06/2014 Projektleitung: Dr. Matthias Schwalbe

• Neue multinukleare Metallkatalysatoren zur lichtgetriebenen Aktivierung von Wasser und zur Reduktion von CO2 (II)

  Quelle ↗

  Förderer: DFG Eigene Stelle (Sachbeihilfe) Zeitraum: 08/2013 - 12/2017 Projektleitung: Dr. Matthias Schwalbe

• SPP 2102: Photokatalytische CO2-Reduktion mit heterodinuklearen Katalysatoren basierend auf gut zugänglichen Metallen

  Quelle ↗

  Förderer: DFG Schwerpunktprogramm Zeitraum: 01/2019 - 12/2022 Projektleitung: Dr. Matthias Schwalbe

• PPI Plastic Products Innovation GmbH & Co KG

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  13 Treffer58.4%
  • Solar Collectors made of Polymers
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    58.4%

• GREENoneTEC Solarindustrie GmbH

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  13 Treffer58.4%
  • Solar Collectors made of Polymers
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    58.4%

• HTCO GmbH - Dr. Axel Müller

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  13 Treffer58.4%
  • Solar Collectors made of Polymers
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    58.4%

• DS Smith Kaysersberg Paper Mill

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  12 Treffer58.4%
  • Solar Collectors made of Polymers
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    58.4%

• POLYTEC PLASTICS Ebensee GmbH

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  12 Treffer58.4%
  • Solar Collectors made of Polymers
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    58.4%

• AVENTA AS

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  14 Treffer58.4%
  • Solar Collectors made of Polymers
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    58.4%

• advanced polymer compounds

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  13 Treffer58.4%
  • Solar Collectors made of Polymers
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    58.4%

• ICS Maugeri SPA

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  10 Treffer55.3%
  • Surface-enhanced Raman spectroscopy in liquid biopsy for breast cancer
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    55.3%

• INL - International Iberian Nanotechnology Laboratory

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  10 Treffer55.3%
  • Surface-enhanced Raman spectroscopy in liquid biopsy for breast cancer
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    55.3%

• Science & Startups Berlin

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  8 Treffer54.9%
  • Zuwendung im Rahmen des Programms „exist – Existenzgründungen aus der Wissenschaft“ aus dem Bundeshaushalt, Einzelplan 09, Kapitel 02, Titel 68607, Haushaltsjahr 2026, sowie aus Mitteln des Europäischen Strukturfonds (hier Euro-päischer Sozialfonds Plus – ESF Plus) Förderperiode 2021-2027 – Kofinanzierung für das Vorhaben: „exist Women“
    T

    54.9%

• Hangman Corroles: Efficient Synthesis and Oxygen Reaction Chemistry

  2010

  Journal of the American Chemical Society · 217 Zitationen · DOI

  The construction of a new class of compounds--the hangman corroles--is provided efficiently by the modification of macrocyclic forming reactions from bilanes. Hangman cobalt corroles are furnished in good yields from a one-pot condensation of dipyrromethane with the aldehyde of a xanthene spacer followed by metal insertion using microwave irradiation. In high oxidation states, X-band EPR spectra and DFT calculations of cobalt corrole axially ligated by chloride are consistent with the description of a Co(III) center residing in the one-electron oxidized corrole macrocycle. These high oxidation states are likely accessed in the activation of O-O bonds. Along these lines, we show that the proton-donating group of the hangman platform works in concert with the redox properties of the corrole to enhance the catalytic activity of O-O bond activation. The hangman corroles show enhanced activity for the selective reduction of oxygen to water as compared to their unmodified counterparts. The oxygen adduct, prior to oxygen reduction, is characterized by EPR and absorption spectroscopy.

• The role of the bridging ligand in photocatalytic supramolecular assemblies for the reduction of protons and carbon dioxide

  2012

  Coordination Chemistry Reviews · 152 Zitationen · DOI

• Photophysics of an Intramolecular Hydrogen‐Evolving Ru–Pd Photocatalyst

  2009

  Chemistry - A European Journal · 142 Zitationen · DOI

  Photoinduced electron-transfer processes within a precatalyst for intramolecular hydrogen evolution [(tbbpy)(2)Ru(tpphz)PdCl(2)](2+) (RuPd; tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine, tpphz = tetrapyrido[3,2-a:2',3'c:3'',2'',-h:2''',3'''-j]phenazine) have been studied by resonance Raman and ultrafast time-resolved absorption spectroscopy. By comparing the photophysics of the [(tbbpy)(2)Ru(tpphz)](2+) subunit Ru with that of the supramolecular catalyst RuPd, the individual electron-transfer steps are assigned to kinetic components, and their dependence on solvent is discussed. The resonance Raman data reveal that the initial excitation of the molecular ensemble is spread over the terminal tbbpy and the tpphz ligands. The subsequent excited-state relaxation of both Ru and RuPd on the picosecond timescale involves formation of the phenazine-centered intraligand charge-transfer state, which in RuPd precedes formation of the Pd-reduced state. The photoreaction in the heterodinuclear supramolecular complex is completed on a subnanosecond timescale. Taken together, the data indicate that mechanistic investigations must focus on potential rate-determining steps other than electron transfer between the photoactive center and the Pd unit. Furthermore, structural variations should be directed towards increasing the directionality of electron transfer and the stability of the charge-separated states.

• High-valent metal-oxo intermediates in energy demanding processes: from dioxygen reduction to water splitting

  2015

  Current Opinion in Chemical Biology · 95 Zitationen · DOI

• Photochemical CO₂ Reduction Catalyzed by Phenanthroline Extended Tetramesityl Porphyrin Complexes Linked with a Rhenium(I) Tricarbonyl Unit

  2015

  Inorganic Chemistry · 75 Zitationen · DOI

  A series of heterodinuclear complexes (M-1-Re) based on a phenanthroline (phen) extended tetramesityl porphyrin ligand (H2-1) has been prepared. The phen moiety of this ligand selectively coordinates a Re(I) tricarbonyl chloride unit, whereas the metal in the porphyrin moiety has been varied: namely, Cu, Pd, Zn, Co, or Fe was used. These dinuclear complexes were fully characterized by standard analytical methods. Additionally, a crystal structure of Cu-1-Re·5.5(C7H8)·0.5(C6H6) could be obtained, and extended time-resolved emission lifetime measurements were conducted. Furthermore, their ability to catalyze the photochemical reduction of CO2 to CO was investigated. Light-driven CO2 reduction experiments were performed in dimethylformamide (DMF) using triethylamine (TEA) as the sacrificial electron donor. The TONs (turnover numbers) of CO were determined and revealed a surprising catalytic activity that is obviously independent from the redox activity of the porphyrin metal. We have recently shown that the parent M-1 compounds are active photocatalysts, but the catalytic activity was dependent on the redox activity of the porphyrin metal. In the case of the new heterodinuclear complexes M-1-Re reported in this study, the catalytic active center seems to be the Re(I) moiety and not the porphyrin. Surprisingly, Zn-1-Re proved to be the most active compound in this series showing a TONCO of 13 after 24 h of illumination using a >375 nm cutoff filter while all other compounds showed minimal activity under this condition.

• Effective intermediate-spin iron in O ₂ -transporting heme proteins

  2017

  Proceedings of the National Academy of Sciences · 63 Zitationen · DOI

  Proteins carrying an iron-porphyrin (heme) cofactor are essential for biological O₂ management. The nature of Fe-O₂ bonding in hemoproteins is debated for decades. We used energy-sampling and rapid-scan X-ray Kβ emission and K-edge absorption spectroscopy as well as quantum chemistry to determine molecular and electronic structures of unligated (deoxy), CO-inhibited (carboxy), and O₂-bound (oxy) hemes in myoglobin (MB) and hemoglobin (HB) solutions and in porphyrin compounds at 20-260 K. Similar metrical and spectral features revealed analogous heme sites in MB and HB and the absence of low-spin (LS) to high-spin (HS) conversion. Amplitudes of Kβ main-line emission spectra were directly related to the formal unpaired Fe(d) spin count, indicating HS Fe(II) in deoxy and LS Fe(II) in carboxy. For oxy, two unpaired Fe(d) spins and, thus by definition, an intermediate-spin iron center, were revealed by our static and kinetic X-ray data, as supported by (time-dependent) density functional theory and complete-active-space self-consistent-field calculations. The emerging Fe-O₂ bonding situation includes in essence a ferrous iron center, minor superoxide character of the noninnocent ligand, significant double-bond properties of the interaction, and three-center electron delocalization as in ozone. It resolves the apparently contradictory classical models of Pauling, Weiss, and McClure/Goddard into a unifying view of O₂ bonding, tuned toward reversible oxygen transport.

• Synthesis and Characterisation of Poly(bipyridine)ruthenium Complexes as Building Blocks for Heterosupramolecular Arrays

  2008

  European Journal of Inorganic Chemistry · 63 Zitationen · DOI

  Abstract Poly(bipyridine)ruthenium complexes with carboxylate anchor groups are key components in dye‐sensitised solar cells. In this contribution, an improved microwave‐assisted synthetic procedure is presented for the important building block [RuCl 2 (dcmb) 2 ] (dcmb = 4,4′‐dimethoxycarbonyl‐2,2′‐bipyridine), which results in short reaction times and high purity. The methyl esters are easily deprotected to give free carboxylate functions. In addition, a full structural, spectral and electrochemical characterisation of a series of complexes with the general formula [Ru(dcmb) 3– n (tbbpy) n ](PF 6 ) 2 with n = 0–3 and tbbpy = 4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridine is presented. The location of the lowest‐energy metal‐to‐ligand charge transfer (MLCT) excited state is investigated by resonance Raman spectroscopy for selected complexes. The results obtained indicate that the nature of the excited state that is populated is dependent on the excitation wavelength. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

• Xanthene-Modified and Hangman Iron Corroles

  2011

  Inorganic Chemistry · 53 Zitationen · DOI

  Iron corroles modified with a xanthene scaffold are delivered from easily available starting materials in abbreviated reaction times. These new iron corroles have been spectroscopically examined with particular emphasis on defining the oxidation state of the metal center. Investigation of their electronic structure using (57)Fe Mössbauer spectroscopy in conjunction with density functional theory (DFT) calculations reveals the non-innocence of the corrole ligand. Although these iron corroles contain a formal Fe(IV) center, the deprotonated corrole macrocycle ligand is one electron oxidized. The electronic ground state of these complexes is best described as an intermediate spin S = 3/2 Fe(III) site strongly antiferromagnetically coupled to the S = 1/2 of the monoradical dianion corrole [Fe(III)Cl-corrole(+•)]. We show here that iron corroles as well as xanthene-modified and hangman xanthene iron corroles are redox active and catalyze the disproportionation of hydrogen peroxide via the catalase reaction, and that this activity scales with the oxidation potential. The meso position of corrole macrocycle is susceptible toward nucleophilic attack during catalase turnover. The reactivity of peroxide within the hangman cleft reported here adds to the emerging theme that corroles are good at catalyzing two-electron activation of the oxygen-oxygen bond in a variety of substrates.

• Efficient Synthesis of Hangman Porphyrins

  2010

  Organic Letters · 47 Zitationen · DOI

  A two-step synthetic method has been designed to furnish hangman porphyrins in good yields from easily available starting materials. The use of the microwave irradiation technique has been found to be valuable for delivering the carboxylic acid hanging group in a much simplified and less time-consuming basic ester hydrolysis (4 h vs 7 days under harsh acidic conditions). The new route facilitates the synthesis of various hangman porphyrins that previously had limited or no access.

• Synthesis and characterization of regioselective substituted tetrapyridophenazine ligands and their Ru(ii) complexes

  2010

  Dalton Transactions · 45 Zitationen · DOI

  A series of novel regioselective substituted tpphz ligands and two novel mononuclear ruthenium complexes of the type [(tbbpy)(2)Ru(tpphzR(n))](PF(6))(2) (where tbbpy = 4,4'-di-tert.-butyl-2,2'-bipyridine, tpphz = tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine, with n = 2 and R represents the bromine substituents at different positions) have been synthesized. All compounds were completely characterized by NMR and MS spectroscopy, absorption and steady-state emission spectroscopy as well as emission lifetime and electrochemical measurements. Additionally the solid-state structures of the two isomers [(tbbpy)(2)Ru(Br(2)tpphz)](PF(6))(2) 6 and [(tbbpy)(2)Ru(tpphzBr(2))](PF(6))(2) 7 are presented and compared with the results of density-functional theory calculations (DFT). Furthermore calculated Raman spectra were obtained by means of DFT calculations and used to assign the vibrational modes of the measured off resonance Raman spectra. A clear influence caused by the electronic effects of the different type and position of the substituents of tpphz on the photophysical behavior was observed.

• The switch that wouldn't switch – unexpected luminescence from a ruthenium(ii)-dppz-complex in water

  2010

  Dalton Transactions · 42 Zitationen · DOI

  The complex [(dmcb)(2)Ru(dppz)](PF(6))(2) shows unexpected luminescence in water implying fundamentally different excited state relaxation pathways than are typically observed for complexes of this kind.

• Sensitized Photochemical CO₂ Reduction by Hetero‐Pacman Compounds Linking a Re^I Tricarbonyl with a Porphyrin Unit

  2019

  Chemistry - A European Journal · 40 Zitationen · DOI

  The hetero-Pacman architecture places two different metal coordination sites in close proximity, which can support efficient energy and/or electron transfer and allow for cooperative activation of small molecules. Here, the synthesis of dyads consisting of a porphyrin unit as photosensitizer and a rhenium unit as catalytically active site, which are held together by the rigid xanthene backbone, is presented. Mononuclear [(NN)Re(CO)₃ (Cl)] complexes for CO₂ reduction in which NN represents a bidentate diimine ligand (e.g., bipyridine or phenanthroline) lack light absorption in the visible region, resulting in poor photocatalysis upon illumination with visible light. To improve their visible-light absorption, we have focused on the incorporation of a strongly absorbing free base or zinc porphyrin unit. Resulting photocatalytic experiments showed a strong dependence of the catalytic performance on both the type of photosensitizer and the excitation wavelengths. Most notably, the intramolecular hetero-Pacman system containing a zinc porphyrin unit showed much better catalytic activity in the visible region (excitation wavelengths >450 nm) than the free base porphyrin version or the corresponding mononuclear rhenium compound or an intermolecular system comprised of a 1:1 mixture of the mononuclear analogues.

• Robust electrografted interfaces on metal oxides for electrocatalysis – an <i>in situ</i> spectroelectrochemical study

  2018

  Journal of Materials Chemistry A · 40 Zitationen · DOI

  <italic>In situ</italic> spectroelectrochemistry demonstrates stability of electrografted diazonium interfaces on conductive oxides &amp; their suitability as anchoring groups for molecular species.

• Pacman Compounds: From Energy Transfer to Cooperative Catalysis

  2017

  Chemistry - A European Journal · 38 Zitationen · DOI

  In this Concept article we present the syntheses and application of homo and heterodinuclear "Pacman" compounds. This architecture implies that two metal coordination fragments are brought in close vicinity to each other via a covalent linkage to either support energy transfer between the two units or cooperative transformation of a substrate. Nature has shown that the combination of metal fragments, in particular two different metals, can dramatically improve the efficiency of small molecule activation. We exemplify this strategy for the activation of water, dioxygen and carbon dioxide. Furthermore, we present artificial systems in which a positive effect on the catalytic performance because of the combination of two (different) metal centers could be observed. Thus, Pacman-type compounds are very well suited as structural and functional models for their biological counterparts.

• Ruthenium polypyridine complexes of tris-(2-pyridyl)-1,3,5-triazine—unusual building blocks for the synthesis of photochemical molecular devices

  2009

  Dalton Transactions · 36 Zitationen · DOI

  The mononuclear compounds bis-(2,2'-bipyridine)ruthenium(ii)-(tris(2-pyridyl)triazine) [(bpy)(2)Ru(tpt)](PF(6))(2) and bis-(4,4'-di-tert-butyl-2,2'-bipyridine)ruthenium(ii)-(tris(2-pyridyl)triazine) [(tbbpy)(2)Ru(tpt)](PF(6))(2) have been synthesised and fully characterised. The attempted syntheses of heterodinuclear complexes with the tris(2-pyridyl)triazine (tpt) ligand as bridging ligand and various palladium(ii)- and platinum(ii)-dichloro complexes using the ruthenium complexes as starting materials resulted in a partial hydrolysis of the triazine based bridging ligand in case of and an unselective decomposition in case of . Compound reacts with Pd(DMSO)(2)Cl(2) and Pt(DMSO)(2)Cl(2) substituting three ligands from the metal centres of these precursors with partial hydrolysis of the triazine moiety of the bridging ligand yielding the dinuclear complexes bis-(4,4'-di-tert-butyl-2,2'-bipyridine)ruthenium(ii)-N-((picolinamido)(pyridin-2-yl)methylene)picolinamide)chloro-palladium(ii) [(tbbpy)(2)Ru(tptO)PdCl](PF(6))(2) and bis-(4,4'-di-tert-butyl-2,2'-bipyridine) ruthenium(ii)-N-((picolinamido)(pyridin-2-yl)methylene)picolinamide)chloro-platinum(ii) [(tbbpy)(2)Ru(tptO)PtCl](PF(6))(2). The newly formed bridging ligand coordinates in a bidentate fashion at the ruthenium centre and acts as a tridentate ligand for the second metal centre. The structures of all the complexes have been fully characterised and their photophysical properties are reported. A similar reaction sequence using the (4'-(p-bromophenyl)-2,2':6',2''-terpyridine)ruthenium(ii)-(tris(2-pyridyl)triazine) complex [(BrPhtpy)Ru(tpt)](PF(6))(2) and Pd(CH(3)CN)(2)Cl(2) as starting materials did not yield the hydrolysed bridging ligand but the expected dinuclear complex [(BrPhtpy)Ru(tpt)PdCl(2)](PF(6))(2) suggesting that the coordination of two pyridine rings of the tpt by the ruthenium centre is essential for the stabilisation of the tpt frame work. Preliminary investigations show that the dinuclear ruthenium-palladium and -platinum complexes are not active catalysts in the light-driven hydrogen production.

• Photocatalytic Generation of Hydrogen Using Dinuclear π‐Extended Porphyrin–Platinum Compounds

  2018

  Chemistry - A European Journal · 35 Zitationen · DOI

  A series of heterodinuclear complexes, M-1-PtX₂ with M=H₂ , Zn, Cu or Co, X=Cl or I, has been synthesized, and first results on their photocatalytic activity in visible light driven proton reduction are presented. The compounds are based on a phenanthroline extended meso-tetramesityl-porphyrin bridging ligand (H₂ -1) incorporating different metal centers in the porphyrin moiety, which functions as a photosensitizer unit. The well-known catalytically active PtX₂ fragment resides in the phenanthroline coordination pocket. The synthesis was optimized, compounds were fully characterized and a solid-state structure could be obtained for selected complexes. Photocatalytic studies in acetonitrile/water mixtures using triethylamine as sacrificial electron donor showed that the activity of the complexes depends strongly on the metal center in the porphyrin moiety as well as the halogen ions bound at the platinum(II) center.

• Unexpected wavelength dependency of the photocatalytic CO₂ reduction performance of the well-known (bpy)Re(CO)₃Cl complex

  2018

  Chemical Communications · 35 Zitationen · DOI

  The selective photocatalytic reduction of CO₂ to CO has often been accomplished using complexes incorporating the Re(CO)₃Cl fragment. We now discovered that the photocatalytic performance of the well-known parent compound (bpy)Re(CO)₃Cl (bpy = 2,2'-bipyridine) surprisingly depends on the illumination wavelengths: the turnover numbers (TONs) measured using various cut-off filters showed an increased photocatalytic activity when irradiated with visible light with wavelengths longer than 450 nm - even if the compound hardly absorbs light in this wavelength region. Therefore, catalytic, spectroscopic and theoretical investigations were performed to explain this exceptional effect.

• Hangman effect on hydrogen peroxide dismutation by Fe(iii) corroles

  2012

  Chemical Communications · 35 Zitationen · DOI

  Hangman Fe(III) corroles catalyse H(2)O(2) disproportionation at a faster rate and display a more pronounced hangman effect than their one electron oxidized analogues owing to their ability to bypass high energy intermediates by redox-leveling derived from the use of the corrole as a non-innocent ligand.

• Electrocatalytic Carbon Dioxide Reduction by Using Cationic Pentamethylcyclopentadienyl–Iridium Complexes with Unsymmetrically Substituted Bipyridine Ligands

  2015

  Chemistry - A European Journal · 34 Zitationen · DOI

  Eight [Ir(bpy)Cp*Cl](+) -type complexes (bpy= bipyridine, Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) containing differently substituted bipyridine ligands were synthesized and characterized. Cyclic voltammetry (CV) of the complexes in Ar-saturated acetonitrile solutions showed that the redox behavior of the complexes could be fine tuned by the electronic properties of the substituted bipyridine ligands. Further CV in CO2 -saturated MeCN/H2 O (9:1, v/v) solutions showed catalytic currents for CO2 reduction. In controlled potential electrolysis experiments (MeCN/MeOH (1:1, v/v), Eapp =-1.80 V vs Ag/AgCl), all of the complexes showed moderate activity in the electrocatalytic reduction of CO2 with good stability over at least 15 hours. This electrocatalytic process was selective toward formic acid, with only traces of dihydrogen or carbon monoxide and occasionally formaldehyde as byproducts. However, the turnover frequencies and current efficiencies were quite low. No direct correlation between the redox potentials of the complexes and their catalytic activity was observed.

• 2^nd coordination sphere controlled electron transfer of iron hangman complexes on electrodes probed by surface enhanced vibrational spectroscopy

  2015

  Chemical Science · 32 Zitationen · DOI

  Iron hangman complexes exhibit improved catalytic properties regarding O₂ and H₂O₂ reduction, which are attributed to the presence of a proton donating group in defined vicinity of the catalytic metal centre. Surface enhanced resonance Raman (SERR) and IR (SEIRA) spectro-electrochemistry has been applied concomitantly for the first time to analyse such iron hangman porphyrin complexes attached to electrodes in aqueous solution. While the SERR spectra yield information about the redox state of the central iron, the SEIRA spectra show protonation and deprotonation events of the 2^nd coordination sphere. To investigate the influence of a proton active hanging group on the heterogeneous electron transfer between the iron porphyrin and the electrode, two hangman complexes with either an acid or ester functional group were compared. Using time resolved SERR spectroscopy the electron transfer rates of both complexes were determined. Complexes with an acid group showed a slow electron transfer rate at neutral pH that increased significantly at pH 4, while complexes with an ester group exhibited a much faster, but pH independent rate. SEIRA measurements were able to determine directly for the first time a p<i>K</i>_a value of 3.4 of a carboxylic hanging group in the immobilized state that shifted to 5.2 in D₂O buffer solution. The kinetic data showed an increase of the heterogeneous electron transfer rate with the protonation degree of the acid groups. From these results, we propose a PCET which is strongly modulated by the protonation state of the acid hanging group <i>via</i> hydrogen bond interactions.

• Elucidation of Cooperativity in CO₂ Reduction Using a Xanthene-Bridged Bimetallic Rhenium(I) Complex

  2020

  ACS Catalysis · 31 Zitationen · DOI

  Mechanistic studies on dinuclear complexes that can activate CO2 are rare. Based on the investigations done for the mononuclear compound (bpy)Re(CO)3Cl (bpy-Re, with bpy = 2,2′-bipyridine), many reports favor a mononuclear catalytic cycle, while the possibility of a dinuclear catalytic species is discussed in the literature in only a few cases. Here, we report the synthesis and characterization of a homobimetallic rhenium(I) compound, in which two (bipyridine)Re(CO)3Cl fragments are brought into close vicinity by attaching them to a xanthene backbone. First, photocatalytic investigations show a significant increase of the catalytic performance compared to the mononuclear parent compound. Second, spectroelectrochemical experiments demonstrate the remarkable fast formation of an intermediate with a Re–Re bond that forms upon reduction of the starting compound, but which is not able to activate CO2. Third, spectroscopic investigations under (photo)catalytic conditions were performed to shed light on the crucial intermediates emerging in the reaction cycle. The assignment of these intermediates is assisted by extensive density functional theory calculations. As a result, the enhanced photocatalytic activity is reasoned by inhibition of deactivation channels and a cooperative reaction mechanism, in which one metal center functions as a photosensitizer to assist the second, catalytically active, metal.

• Tuning of photocatalytic activity by creating a tridentate coordination sphere for palladium

  2014

  Dalton Transactions · 25 Zitationen · DOI

  The synthesis and characterisation of an asymmetric potential bridging ligand bmptpphz (bmptpphz = 2,17-bis(4-methoxyphenyl)tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j] phenazine) is presented. This ligand contains a 1,10-phenanthroline (phen) and a 2,9-disubstituted phen sphere and possesses a strong absorbance in the visible. Facile coordination of the phen sphere to a Ru(tbbpy)2 core leads to Ru(bmptpphz) ([(tbbpy)2Ru(bmptpphz)](PF6)2; tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine). UV-vis, emission, resonance Raman and theoretical investigations show that this complex possesses all properties associated with a Ru(tpphz) ([(tbbpy)2Ru(tpphz)](PF6)2; tpphz = tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j] phenazine) moiety and that the ligand based absorbances in the vis-part also populate an MLCT like state. The coordination of a Pd-core in the new 2,9-disubstituted phen sphere is possible, leading to a cyclometallation. The tridentate complexation leads to changes in the UV-vis and emission behaviour. Furthermore, the stability of the Pd-coordination is significantly enhanced if compared to the unsubstituted Ru(tpphz). Ru(bmptpphz)PdCl proved to be an active photocatalyst for H2 evolution, albeit with lower activity than the mother compound Ru(tpphz)PdCl2.

• Synthesis of sterically hindered xanthene-modified iron corroles with catalase-like activity

  2013

  Chemical Communications · 25 Zitationen · DOI

  An up to 18-fold increase of the turnover frequency (TOF) in the catalase-like hydrogen peroxide dismutation reaction is observed by incorporation of substituents in the β-position of xanthene-modified iron corroles.

• Photochemical CO₂-reduction catalyzed by mono- and dinuclear phenanthroline-extended tetramesityl porphyrin complexes

  2015

  Dalton Transactions · 23 Zitationen · DOI

  We here present a comprehensive study on the light-induced catalytic CO2 reduction employing a number of mono- and dinuclear complexes with a phenanthroline-extended tetramesityl porphyrin ligand (). A stepwise synthesis of heterodinuclear complexes is possible because the phenanthroline moiety of the ligand can selectively coordinate a second metal center, e.g. Ru(tbbpy)2(2+) fragment, while any other metal can reside in the porphyrin cavity. We expanded our former studies to cobalt and iron compounds and synthesized the complexes , and , . Thorough catalytic investigation on the light-driven CO2 reduction of all compounds (M = 2H, Cu, Pd, Co, FeCl) was performed in a DMF solution in the presence of triethylamine (TEA) as a sacrificial electron donor. A very surprising wavelength dependence of the catalytic performance was observed. Turnover numbers (TONs) of CO were quantified and showed that redox active metals (i.e.M = Co and FeCl) in the porphyrin cavity caused the highest catalytic activity. After 24 hours of illumination with light λ > 305 nm reached a TONCO of 11.4 with our experimental setup without showing much decomposition. This value is twice as high as the TONCO determined for CoTPP (5.8) under the same conditions, which represented the most active porphyrinic system so far for photocatalytic CO2 reduction.

• An Iron Porphyrin Complex with Pendant Pyridine Substituents Facilitates Electrocatalytic CO₂ Reduction via Second Coordination Sphere Effects

  2021

  ChemCatChem · 22 Zitationen · DOI

  Abstract A bispyridylamine‐based hanging unit within the ligand framework of a newly synthesized iron porphyrin complex ( Py 2 XPFe ) can act, on the one hand, as a hydrogen bonding site to facilitate proton transfer in catalysis and, on the other hand, as coordination site for a second Lewis acidic metal center. The bispyridylamine group in close proximity of the iron porphyrin center is able to mediate electrocatalytic CO 2 reduction in anhydrous MeCN. The hydrogen bonding interactions within the hanging group affect the kinetics of catalysis likely through stabilization of the [Fe I (CO 2 H)] − intermediate, increasing the overall rate of catalysis when compared to the non‐functionalized analog, TMPFe (TMP=tetramesitylporphyrin). The rate constants ( k app ) of the reduction reaction were calculated using the FOWA method which resulted in a higher TOF max for the complex Py 2 XPFe compared with TMPFe in neat MeCN (1.7×10 2 vs. 1.1×10 1 s −1 ). The addition of weak Brønsted acids to the reaction mixture (TFE or PhOH) shows an increase in the rate of catalysis for both complexes, yet the Py 2 XPFe analog displays higher TOF max at each relative acid concentration, suggesting the hanging group beneficially impacts the rate of catalysis in the presence of these proton sources. The addition of Lewis acidic Sc 3+ to Py 2 XPFe also results in an increase in current density of the CO 2 reduction reaction. Resonance Raman as well as 1 H‐NMR spectroscopy indicates coordination to the pyridine substituents.

• Charité – Universitätsmedizin Berlin

  EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  university

• Freie Universität Berlin

  EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  university

• Fritz-Haber-Institut der Max-Planck-Gesellschaft

  EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  other

• Helmholtz-Zentrum Berlin für Materialien und Energie

  EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  other

• Leibniz-Forschungsinstitut für Molekulare Pharmakologie

  EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  other

• Max-Planck-Institut für Kolloid- und Grenzflächenforschung

  EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  other

• Technische Universität Berlin

  Die Aufdeckung des photo-induzierten Assemblierungsmechanismus des lichtgetriebenen Wasseroxidationskomplexes in Photosystem II

  university

• Universität Basel

  SPP 2102: Photokatalytische CO2-Reduktion mit heterodinuklearen Katalysatoren basierend auf gut zugänglichen Metallen

  university

• Universität Potsdam

  EXC 2008: Unifying Systems in Catalysis (UniSysCat)

  university

Name

Dr. Matthias Schwalbe

Titel

Dr.

Fakultät

Mathematisch-Naturwissenschaftliche Fakultät

Institut

Institut für Chemie

Arbeitsgruppe

Anorganische und Allgemeine Chemie I

Telefon

+49 30 2093-7571

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Zuletzt gescrapt

26.4.2026, 01:12:25