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EPR, Raman and hydrogen production

Der Fokus unserer Gruppe liegt auf dem Verständnis allgemeiner Prozesse in der Katalyse durch spektroskopische Untersuchung der elektronischen Struktur von Reaktions-Zwischenprodukten. Unsere Hauptforschungsmethoden sind die Resonanz-Raman-Spektroskopie, die Elektronen-Paramagnetische Resonanz-Spektroskopie (EPR) sowie die Quantenchemie. Die Kenntnis der elektronischen Struktur von katalytischen Zwischenprodukten ist von entscheidender Bedeutung, denn es sind die Elektronen, die in nahezu allen katalytischen Prozessen, die fast ausnahmslos auf der Redox-Chemie basieren, eine Hauptrolle spielen. Wann immer Elektronen in Bewegung sind, ist die Kenntnis, wo sich die redoxaktiven Elektronen befinden, z.B. in Form von Donor- und Akzeptororbitalen, sowohl für das Verständnis als auch für die schrittweise Verbesserung der Katalysatoren entscheidend. Darüber hinaus kann die durch die Kombination dieser Methoden gewonnene Erkenntnis auch die Identifizierung von Übergangszuständen und Energiebarrieren ermöglichen, die möglicherweise überwunden werden müssen, um die Katalyse weiter zu verbessern.

Maurice van Gastel

Dr. Maurice van Gastel

2018
Gruppenleiter am Max-Planck-Institut für Kohlenforschung
2005-2017
Gruppenleiter am MPI für Bioanorganische Chemie; heute: MPI CEC
2009-2011
Hochschullehrer an der Universität Bonn
2002-2005
Postdoc am MPI für Bioanorganische Chemie; heute MPI CEC
2000
Promotion an der Universität von Leiden, Niederlande
1995
Master (Diplom) an der Universität von Leiden, Niederlande
seit 2015
Ombudsmann für gute wissenschaftliche Praxis

 

  • Kalläne SI, van Gastel M Raman spectroscopy as a method to investigate catalytic intermediates: CO2 reducing [Re(Cl)bpy-R(CO)3] catalyst J. Phys. Chem. A 120, 7465-7474, 2016
  • Chu W-Y, Gilbert-Wilson R, Rauchfuss TB, van Gastel M, Neese F Cobalt Phosphino-alpha-iminopyridine-catalyzed hydrofunctionalization of alkenes: catalyst development and mechanistic aspects Organometallics 35, 2900-2914, 2016
  • Das R, Neese F, van Gastel M Hydrogen evolution in [NiFe] hydrogenases and related biomimetic systems: similarities and differences Phys. Chem. Chem. Phys. 18, 24681-24692, 2016
  • Ogata H, Kraemer T, Wang HX, Schilter D, Pelmenschikov V, van Gastel M, Neese F, Rauchfuss TB, Gee LB, Scott AD, Yoda Y, Tanaka Y, Lubitz W, Cramer SP Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy Nat. Comm. 6, 7890, 2015
  • Kochem A, Gellon G, Jarjayes O, Philouze C, d’Hardemare AD, van Gastel M, Thomas F Nickel(II) radical complexes of thiosemicarbazone ligands appended by salicylidene, aminophenol and aminothiophenol moieties Dalton Trans 44, 12743-12756, 2015
  • Kochem A, O’Hagan M, Wiedner, ES, van Gastel M Combined spectroscopic and electrochemical detection of a NiI…H-N bonding interaction with relevance to electrocatalytic hydrogen production Chem. Eur. J. 21, 10338-10347, 2015
  • Barilone J, Ogata H, Lubitz W, van Gastel M Structural differences between the active sites of the Ni-A and Ni-B states of the [NiFe] hydrogenase: an approach by quantum chemistry and single crystal ENDOR spectroscopy Phys. Chem. Chem. Phys. 17, 16204-16212, 2015
  • Kochem A, Weyhermüller T, Neese F, van Gastel M EPR and quantum chemical investigation of a bioinspired hydrogenase model with a redox-active ligand in the first coordination sphere Organometallics 34, 995-1000, 2015
  • Kochem A, Bill E, Neese F, van Gastel M Mössbauer and computational investigation of a functional [NiFe] hydrogenase complex Chem. Commun. 51, 2099-2102, 2015
  • Barilone J, Neese F, van Gastel M Finding the reactive electron in paramagnetic systems: a critical evaluation of accuracies for EPR spectroscopy and density functional theory using 1,3,5-triphenyl verdazyl radical as a testcase Appl. Magn. Res. 46, 117-139, 2015
  • Zolnhofer EM, Käss M, Khusniyarov MM, Heinemann FW, Maron L, van Gastel M, Bill E, Meyer K An intermediate Cobalt(IV)nitrido complex and its N-migratory insertion product J. Am. Chem. Soc. 136, 15072-15078, 2014
  • Kochem A, Carrillo A, Philouze C, van Gastel M, d’Hardemare AD, Thomas F Copper(II)-coordinated alpha-azophenols: effect of the metal-ioin geometry on phenoxyl/phenolate oxidation potential and reactivity Eur. J. Inorg. Chem. 26, 4263-4267, 2014
  • Rudolph R, Blom B, Yao S, Meier F, Bill E, van Gastel M, Lindenmaier N, Kaupp M, Driess M Synthesis, reactivity, and electronic structure of a bioinspired heterobimetallic Ni(m-S2)Fe complex with disulfur monoradical character Organometallics 33, 3154-3162, 2014
  • Marchanka A, Lubitz W, Plato M, van Gastel M Comparative ENDOR study at 34 GHz of the triplet state of the primary donor in bacterial reaction centers of Rb. Sphaeroides and Bl. Viridies Photosyn. Res. 120, 99-111, 2014
  • Kochem A, Gellon G, Jarjayes O, Philouze C, Leconte N, van Gastel M, Bill E, Thomas F A singlet ground state for a cobalt(II)-anilinosalen radical complex dagger Chem. Commun. 38, 4924-4926, 2014
  • Asami K, Takashina A, Kobayashi M, Iwatsuki S, Yajima T, Kochem A, van Gastel M, Tani F, Kohzuma T, Thomas F, Shimazaki Y Characterization of one-electron oxidized copper(II)-salophen-type complexes; effects of electronic and geometrical structures on reactivities Dalton Trans 43, 2283-2293, 2014
  • Kochem A, Thomas F, Jarjayes O, Gellon G, Philouze C, Weyhermüller T, Neese F, van Gastel M Hydrogen Generation by an Anilinosalen Cobalt Complex containing Proton Relays in the First Coordination Sphere Inorg. Chem. 52, 14428-14438, 2013
  • Kochem A, Neese F, van Gastel, M A Spectroscopic and Quantum Chemical Study of the Ni(PPh2NC6H4CH2P(O)(OEt)22)2 Electrocatalyst for Hydrogen Production J. Phys. Chem. C. 118, 2350-2360, 2014
  • Cangönül A, Behlendorf M, Gansäuer A, van Gastel M Radical-Based Epoxide Opening by Titanocenes Inorg. Chem. 52, 11859-11866, 2013
  • Krämer T, Kampa M, Lubitz W, van Gastel M, Neese F Theoretical Spectroscopy of the NiII Intermediate States in the Catalytic Cycle and the Activation of [NiFe] Hydrogenases ChemBioChem 14, 1898-1905, 2013
  • Kampa M, Pandelia ME, Lubitz W, van Gastel M, Neese F A Metal−Metal Bond in the Light-Induced State of [NiFe] Hydrogenases with Relevance to Hydrogen Evolution J. Am. Chem. Soc. 135, 3915-3925, 2013
  • Weber  K. Krämer T., Shafaat HS, Weyhermüller T, Bill E, van Gastel M, Neese F, Lubitz W A Functional [NiFe]-Hydrogenase Model Compound That Undergoes Biologically Relevant Reversible Thiolate Protonation J. Am. Chem. Soc. 134, 20745-20755, 2012
  • Kampa M, Lubitz W, van Gastel M, Neese F Computational study of the electronic structure and magnetic properties of the Ni-C state in [NiFe] hydrogenases including the second coordination sphere J. Biol. Inorg. Chem. 17, 1269-1281, 2012
  • Kammler L, van Gastel M Electronic structure of the lowest triplet state of flavin mononucleotide J. Phys. Chem. A 116, 10090-10098, 2012
  • Albrecht C, Shi LL, Perez JM, van Gastel M, Schwieger S, Neese F, Streubel R Deoxygenation of Coordinated Oxaphosphiranes: A New Route to P=C Double-Bond Systems Chem. Eur. J. 18, 9780-9783, 2012
  • Nesterov V, Özbolat-Schön A, Schnakenburg G, Shi LL, Cangönül A, van Gastel M, Neese F, Streubel R An Unusal Case of Facile Non-Degenerate P-C Bond Making and BreakingChem. Asian J. 7, 1708-1712, 2012
  • Marchanka A., van Gastel M. Reversed Freeze Quench Method near the Solvent Phase Transition J. Phys. Chem. A 116, 3899-3906, 2012

Book chapters

  • De Beer S, van Gastel M, Bill E, Ye S, Petrenko T, Pantazis DA, Neese F Challenges in molecular energy research In CHEMICAL ENRGY STORAGE, R. Schlögl (Ed.), De Gruyter, Berlin, 2013

Full publicationslist

Researcher ID

Forschungsthemen

Energy and Hydrogen
Energy and Hydrogen

Energy and Hydrogen

The hydrogen economy represents a way of fulfilling our need for energy by using molecular hydrogen as an energy carrier and using reactions in which polluting products like greenhouse gases are avoided. The prospects of such an economy require the development of clean and efficient ways of producing and storing molecular hydrogen, or, in an extended sense, of molecules by which energy is stored in their chemical bonds.

Presently, the most common methods for the production of molecular hydrogen on an industrial basis concern firstly, steam reforming, a process in which steam is allowed to react with fossil fuels at high temperatures. The energy required (i.e., the enthalpy change ΔH), for, e.g., methane steam reforming
CH4 + H2O → CO + 3 H2
amounts to +49 kcal/mol.1 Secondly, a well-established and widely applied method for hydrogen production, introduced during the early days of electrochemistry in 1800, and which has recently become commercially available, concerns electrolysis of water,
2 H2O → 2 H2 + O2
which requires +116 kcal/mol.1 For comparison, the bond dissociation energy of H2 amounts to +104 kcal/mol.1 These numbers indicate that the production of molecular hydrogen, the key ingredient of the hydrogen economy, is by no means a trivial task, and that the presently used industrial processes to produce molecular hydrogen will in the long term likely not be sustainable.
Fortunately, Nature, has found a way to produce molecular hydrogen very efficiently, by using proteins as catalysts for this reaction. The proteins that evolve hydrogen are called hydrogenases and they catalyze both the formation and the decomposition of molecular hydrogen
H2 → 2 H+ + 2e          (1)

he family of hydrogenases is presently subdivided into three classes, depending on the metal content of the active site.[2] The classes comprise [NiFe], [FeFe] and [Fe] hydrogenases. The turnover numbers for hydrogen production of the [FeFe] hydrogenases amount to 9000 molecules per second.[3] A disadvantage is their oxygen sensitivity, especially for the [FeFe] hydrogenases. The active sites of the [NiFe] and [FeFe] hydrogenases display an unusual arrangement, which includes inorganic CO and CN ligands (see figure 1). In the case of the [FeFe] hydrogenase, the enzyme contains a [4Fe4S] cluster coupled to a [2Fe2S] cluster, which are both clusters are only embedded in the protein by the cysteine thiolate ligands.

In general, the active sites of both classes of hydrogenases contain one free coordination position, which is most likely the catalytically relevant coordination position.[2] For the [NiFe] hydrogenases, which display a rich redox structure in which the nickel atom switches back and forth between the 3+ and 2+ redox state and the iron is 2+, low spin, a hydride ligand has been detected using HYSCORE spectroscopy,[4] which is direct evidence that the catalytic activity indeed occurs at the free coordination position of nickel. Presently, research emphasizes on improving the issue of oxygen sensitivity. In this respect the hydrogenases from extremophile organisms are promising candidates, since these enzymes are much more robust, oxygen insensitive and even function at elevated temperatures.

In a broader sense, besides the H-H bond, Nature often stores energy in chemical bonds of reduced molecules. Well known examples are, e.g., nicotinamide adenine dinucleotide (NADH) or Nicotinamide adenine dinucleotide phosphate (NADPH). As with molecular hydrogen, the energy stored in the respective C-H bonds can be released at any convenient time in an oxidizing environment. Moreover, by the storage of energy in chemical bonds as opposed to charge separation, Nature has greatly simplified the issue of energy storage. Besides NADH, another common molecule is adenosine triphosphate (ATP), in which energy (app. −7 kcal/mol) is stored in the P-O bond. These molecules are common “fuels” employed by Nature to store energy. Additionally, in plant photosynthesis, light energy is converted and stored as sugars (see section e).

The active sites of hydrogenases have been a focal point for inorganic chemists with the aim to prepare biomimetic inorganic molecules that possess catalytic activity. One of the first molecules, which did show catalytic activity towards the splitting of hydrogen in aqueous solution, has been reported by Ogo et al.[5] This molecule features a nickel-ruthenium dinuclear metal center, which is shown to be bridged by a hydride by neutron diffraction studies. The hydride could additionally be shown to be the product of the heterolytic cleavage of molecular hydrogen. Other systems which show catalytic activity in organic solvents involve homonuclear metal centers featuring ruthenium or iridium.

Given these promising initial successes, the challenges for the future still remain many in number. On the one hand, it is of crucial importance to examine the oxygen sensitivity of hydrogenases. On the other hand, the synthesis of inorganic complexes has recently resulted in catalytic activity towards hydrogen production, and should be extended to optimize activity and stability. Thirdly, research efforts are also going into the direction of storing energy in the form of other reduced molecules, i.e., sugars and biomass in a broader sense. Eventually, either of these paths will have to be upscaled to mass production. With fossil fuels being available for only a few more decades, it is clear that the process of energy conversion and storage from alternate sources is a pressing problem and it presently still unknown which path will lead to definite successes first.

References

  1. Handbook of Chemistry and Physics, 81st edition, CRC Press New York (2000).
  2. Chemical Reviews 2007, 107, issue 10 "Hydrogen"
  3. Cammack, R., Nature 1999, 397, 214-215.
  4. Brecht, M.; van Gastel, M.; Buhrke, T.; Friedrich, B.; Lubitz, W. J. Am. Chem. Soc. 2003, 125, 13075-13083.
  5. Ogo, S.; Kabe, R.; Uehara, K.; Kure, B.; Nishimura, T.; Menon, S. C.; Harada, R.; Fukuzumi, S.;  Higuchi, Y.; Ohhara, T.; Tamara, T.; Kuroki, R. Science 2007, 316, 585-587.
Calculation of EPR observables
Calculation of EPR observables

Calculation of EPR observables

In the past few years, great steps forward have been achieved in the field of quantum chemistry with respect to the calculation of EPR parameters, including g values, hyperfine coupling constants and zero field splitting parameters. In the latter case, however, the comparison with calculated zero field splitting parameters by state-of-the-art quantum chemical methods still sometimes gives rise to mediocre agreement. Though the D parameter is usually satisfactorily reproduced when DFT-based methodology is employed, the calculated E parameter does not show a correlation with its experimental counterpart. And even worse, when calculations are performed within a spin-unrestricted formalism, the correlation between the calculated and experimental D parameter is lost completely. In a recent publication, our group has shown that spin polarization is critical for the calculation of zero-field-splitting parameters. Spin polarization effects are difficult to calculate for larger molecules, since it requires the correlation of many electrons – two for each sigma bond present in the molecule - by configuration interaction. In this project, we use a basis of spin-adapted correlated wave functions as a replacement for the widely used Slater determinant and investigate whether these basis functions allow a more accurate calculation of EPR parameters.

 

 

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  •  Dennis Skerra

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  • Dr. Maurice van Gastel

    Dr. van Gastel, Maurice

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