AG Engeser: Research
© LS
AG Engeser: Research
© L. Spenst
AG Engeser: Research
© L. Spenst
AG Engeser: Research
AG Engeser: Research
AG Engeser: Research

Research in the Engeser Group

Our research combines chemical synthesis and modern mass spectrometric methods to answer chemical questions and analyze exciting samples. Mass spectrometers with various ionization methods are used, which are operated in the mass spectrometry facility of the Chemical Institute at the University of Bonn. A laboratory with standard equipment for organic and organometallic chemistry is available for the synthesis of the required molecules. We also cooperate with various national and international working groups.

Mechanismen.png
© AW

Reaction Mechanisms

A main focus of our research currently lies on mechanisms of chemical reactions both in solution and in the gas phase. Electrospray ionization allows a glimpse on what happens in reacting solutions, also for low-abundant, paramagnetic or rapidly interconverting species. The molecular formulae of the observed ions can be determined via accurate mass determinations; the oxidation state can be deduced from the charge state. Furthermore, information about the structure of the observed molecules can be obtained by induced fragmentation of mass-selected species (MS/MS). The FT-ICR device in particular is ideally equipped for such purposes. In addition, ion/molecule reactions can be carried out in the gas phase within the FT-ICR cell, so that the intrinsic reactivities of the examined species become accessible. Comparing the behavior in solution and in the gas phase then provides insights into the influence of solvation. We are currently working on reactions in the areas of organocatalysis and organometallics.

  • Experimental investigation of an oxidative C-C coupling reaction catalyzed by HAuCl4
    M. T. S. Krause, K. Schuppener, H. A. Wegner, M. Engeser, Isr. J. Chem. 2023, 63, e2023000.
    DOI: 10.1002/ijch.202300071
     
  • Probing the gas-phase structure of charge-tagged intermediates of a proline catalyzed aldol reaction – Vibrational spectroscopy distinguishes oxazolidinone from enamine species
    J. A. Willms, J. Vidic, J. Barthelmes, V. Steinmetz, T. Bredow, P. Maître, M. Engeser, Phys. Chem. Chem. Phys. 2019, 21, 2578 - 2586.
    DOI: 10.1039/C8CP04905J
     
  • Mechanistic studies of a L-proline-catalyzed pyridazine formation involving a Diels-Alder reaction with inverse electron demand
    A. Schnell, J. A. Willms, S. Nozinovic, M. Engeser, Beilstein J. Org. Chem. 2019, 15, 30-43.
    DOI: 10.3762/bjoc.15.3
     
  • Investigations of the copper catalyzed oxidative cross-coupling of THIQs with diethylzinc with a combination of mass spectrometric and electrochemical methods
    J. A. Willms, H. Gleich, M. Schrempp, D. Menche, M. Engeser, Chem. Eur. J. 2018, 24, 2663-2668.
    DOI: 10.1002/chem.201704914
     
  • A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry
    J. A. Willms, R. Beel, M. L. Schmidt, C. Mundt, M. Engeser,  Beilstein J. Org. Chem. 2014, 10, 2027-2037.
    DOI: 10.3762/bjoc.10.211
     
  • Iron azides with cyclam derived ligands: Are they precursors for high-valent iron nitrides in the gas phase?
    O. Krahe, F. Neese, M. Engeser, ChemPlusChem  2013, 78, 1053-1057.
    DOI: 10.1002/cplu.201300182
     
  • Direct experimental evidence for an enamine radical cation in SOMO catalysis
    R. Beel, S. Kobialka, M. L. Schmidt, M. Engeser, Chem. Comm. 2011, 47, 3293-3295.  
    DOI: 10.1039/c0cc05347c
     
  • Room-Temperature C-H Bond Activation of Methane by Bare [P4O10] .+
    N. Dietl, M. Engeser, H. Schwarz, Angew. Chem. 2009, 121, 4955-4957; Angew. Chem. Int. Ed. 2009, 48, 4861-4863.
    DOI: 10.1002/ange.200901596 bzw. 10.1002/anie.200901596
    highlighted in:
     R. H. Crabtree, Nature Chemistry 2009, 1, 348-349. DOI: 10.1038/nchem.311
     
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© MK

Supramolecular Chemistry

Our central topics in supramolecular chemistry :   

  • Mass spectrometric characterization of labile supramolecular assemblies
  • Gas-phase fragmentations
  • Exchange processes in solution and in the gas phase
  • Aurophilic interactions
  • Coinage metal complexes with NHC ligands
  • Charge-State-Dependent Fragmentation of [2.2]Paracyclophane-Based Metallosupramolecular Cyclic Helicates in the Gas Phase
    J. Anhäuser, A. Lützen, M. Engeser, ChemPlusChem 2020, 85, 2528-2533.
    DOI: 10.1002/cplu.202000697

  • [2.2]Paracyclophane bis(pyridine)-based metallosupramolecular rhombs in the gas phase: Competitive cleavage of non-covalent and weak covalent bonds
    Y. Lorenz, J. Anhäuser, A. Lützen, M. Engeser, J. Am. Soc. Mass Spectrom. 2019, 30, 2007-2013.
    DOI: 10.1007/s13361-019-02218-2

  • Bond dissociation energies of metallosupramolecular building blocks: Insight from fragmentation of selectively self-assembled heterometallic metallo-supramolecular aggregates
    Y. Lorenz, A. Gutiérrez, M. Ferrer, M. Engeser, Inorg. Chem. 2018, 57, 7346-7354.
    DOI: 10.1021/acs.inorgchem.8b00930

  • Enantiomerically Pure Trinuclear Helicates via Diastereoselective Self-Assembly and Characterization of their Redox Chemistry
    C. Gütz, R. Hovorka, N. Struch, J. Bunzen, G. Meyer-Eppler, Z.-W. Qu, S. Grimme, M. Cetina, F. Topić, K. Rissanen, M. Engeser, A. Lützen, J. Am. Chem. Soc. 2014, 136, 11830-11838.
    DOI: 10.1021/ja506327c

  • Electron capture dissociation of a self-assembled tetranuclear metallosupramolecular complex in the gas phase
    R. Hovorka, M. Engeser, A. Lützen,  Int. J. Mass Spectrom.  2013, 354, 152-158.
    DOI: 10.1016/j.ijms.2013.07.002

  • 3D Au-Ag heterometallic supramolecular cage. Triplet capture by heavy atom effect
    L. Rodríguez, J.C. Lima, M. Ferrer, O. Rossell, M. Engeser, Inorg. Chim. Acta 2012, 381, 195-202. DOI: 10.1016/j.ica.2011.09.038

  • Reactivity of Self-Assembled Supramolecular Complexes in the Gas Phase: A Supramolecular Neighbor Group Effect
    M. Engeser, A. Rang, M. Ferrer, A. Gutierrez, H. T. Baytekin, C. A. Schalley, Int. J. Mass Spectrom. 2006, 255/256, 185-194.
    DOI: 10.1016/j.ijms.2006.01.002
  • A family of heterobimetallic cubes shows spin-crossover behaviour near room temperature
    M. Hardy, J. Tessarolo, J. J. Holstein, N. Struch, N. Wagner, R. Weisbarth, M. Engeser, J. Beck, S. Horiuchi, G. H. Clever, A. Lützen, Angew. Chem. 2021, 133, 22736-22743.
    DOI: 10.1002/ange.202108792
     
  • Self-Assembled Highly Positively Charged Allyl-Pd Crowns: Cavity-Pocket Driven Interactions of Fluoroanions.
    M. Ferrer, A. Gallen, A. Gutiérrez, M. Martínez, E. Ruiz, Y. Lorenz, M. Engeser, Chem. Eur. J. 2020, 26, 7847 –7860.
    DOI: 10.1002/chem.202000316
     
  • Dynamic Complex-to-Complex Transformations of Heterobimetallic Systems Influence the Cage Structure of Spin State of Iron(II) Ions
    M. Hardy, N. Struch, J. J. Holstein, G. Schnakenburg, N. Wagner, M. Engeser, J. Beck, G. H. Clever, A. Lützen, Angew. Chem. 2020, 132, 3221-3226.
    DOI: 10.1002/ange.201914629
     
  • Subcomponent self-assembly of a cyclic tetranuclear Fe(II) helicate in a highly diastereoselective self-sorting manner
    J. Anhäuser, R. Puttreddy, L. Glanz, A. Schneider, M. Engeser, K. Rissanen, A. Lützen, Chem. Eur. J. 2019, 25, 12294-12297.
    DOI: 10.1002/chem.201903164
     
  • Chiral hydrogen-bonded supramolecular capsules: synthesis, characterization and complexation of C70
    M. Kohlhaas, M, Zähres, C. Mayer, M. Engeser, C. Merten, J. Niemeyer, Chem. Commun. 2019, 55, 3298-3301.
    DOI: 10.1039/c8cc10152c
     
  • Chiral self-sorting behaviour of [2.2]paracyclophane-based bis(pyridine) ligands
    J. Anhäuser, R. Puttreddy, Y. Lorenz, A. Schneider, M. Engeser, K. Rissanen, A. Lützen, Org. Chem. Front. 2019, 6, 1226-1235.
    DOI: 10.1039/C9QO00155G
     
  • Ein achtkerniger metallosupramolekularer Würfel mit Spin-Crossover-Eigenschaften
    N. Struch, C. Bannwarth, T.K. Ronson, Y. Lorenz, B. Mienert, N. Wagner, M. Engeser, E. Bill, R. Puttreddy, K. Rissanen, K. Beck, S. Grimme, J.R. Nitschke, A. Lützen, Angew. Chem. 2017, 129, 5012-5017.
    DOI: 10.1002/ange.201700832
     
  • Kinetico-Mechanistic Insights on the Assembling Dynamics of Allyl-Pd Metallamacrocycles; the Pt-Npy bond is the Keystone
    I. Angurell, M. Ferrer, A. Gutiérrez, M. Martínez, M. Rocamora, L. Rodríguez, O. Rossell, Y. Lorenz, M. Engeser, Chem. Eur. J. 2014, 20, 14473-14487.
    DOI: 10.1002/chem.201403467
     
  • Unexpected Self-Assembly of a Homochiral Metallosupramolecular M4L4-Catenane
    R. Hovorka, G. Meyer-Eppler, T. Piehler, S. Hytteballe, M. Engeser, F. Topić, K. Rissanen, A. Lützen, Chem. Eur. J. 2014, 20, 13253-13258.
    DOI: 10.1002/chem.201403414
     
  • Enantiomerically Pure Trinuclear Helicates via Diastereoselective Self-Assembly and Characterization of their Redox Chemistry
    C. Gütz, R. Hovorka, N. Struch, J. Bunzen, G. Meyer-Eppler, Z.-W. Qu, S. Grimme, M. Cetina, F. Topić, K. Rissanen, M. Engeser, A. Lützen, J. Am. Chem. Soc. 2014, 136, 11830-11838.
    DOI: 10.1021/ja506327c
     
  • Enantiomerically Pure M6L12 or M12L24-Polyhedra from Flexible Bis(Pyridine) Ligands
    C. Gütz, R. Hovorka, C. Klein, Q.-Q. Jiang, C. Bannwarth, M. Engeser, C. Schmuck, W. Assenmacher, W. Mader, F. Topić, F. Rissanen, S. Grimme, A. Lützen,  Angew. Chem. 2014, 126, 1719-1724.
    DOI: 10.1002/ange.201308651
     
  • Heteroleptic Metallosupramolecular Racks, Rectangles and Trigonal Prisms: Stoichiometry-Controlled Reversible Interconversion
    S. Neogi, Y. Lorenz, M. Engeser, D. Samanta, M. Schmittel, Inorg. Chem. 2013, 52, 6975-6984.
    DOI: 10.1021/ic400328d

  • Implications of Stoichiometry-Controlled Structural Changeover Between Heteroleptic Trigonal [Cu(phenAr2)(py)]+ and Tetragonal [Cu(phenAr2)(py)2]+ Motifs for Solution and Solid-State Supramolecular Self-Assembly.
    S. Neogi,  G. Schnakenburg, Y. Lorenz, M. Engeser, M. Schmittel, Inorg. Chem. 2012, 51, 10832-10841.
    DOI: 10.1021/ic301286w
     
  • Self-Assembly of heterometallic metallomacrocycles via ditopic Fluoroaryl Gold(I) Organometallic Metalloligands
    M. Ferrer, A. Gutiérrez, L. Rodríguez, O. Rossell, E. Ruiz, M. Engeser, Y. Lorenz, R. Schilling, P. Gómez-Sahl, A. Martín, Organometallics 2012, 31, 1533-1545.
    DOI: 10.1021/om201028q
     
  • 3D Au-Ag heterometallic supramolecular cage. Triplet capture by heavy atom effect
    L. Rodríguez, J.C. Lima, M. Ferrer, O. Rossell, M. Engeser, Inorg. Chim. Acta 2012, 381, 195-202.
    DOI: 10.1016/j.ica.2011.09.038
     
  • Antisymbiotic Self-Assembly and Dynamic Behavior of Metallamacrocycles with Allylic Corners
    I. Angurell, M. Ferrer, A. Gutiérrez, M. Martínez, L. Rodríguez, O. Rossell, M. Engeser, Chem. Eur. J. 2010, 16, 13960-13964.
    DOI: 10.1002/chem.201002605
     
  • Magnetic coupling in enaniomerically pure trinuclear helicate-type complexes formed by hierarchical self-assembly
    M. Albrecht, M. Fiege, P. Kögerler, M. Speldrich, R. Fröhlich, M. Engeser, Chem. Eur. J. 2010, 16, 8797-8804.
    DOI: 10.1002/chem.200903108
     
  • Cap for Copper(I) Ions! Metallosupramolecular Solid and Solution State Structures on the Basis of the Dynamic Tetrahedral [Cu(phenAr2)(py)2]+ Motif
    M. Schmittel, B. He, J. Fan, J.W. Bats, M. Engeser, M. Schlosser, H. Deiseroth, Inorg. Chem. 2009, 48, 8192-8200.
    DOI: 10.1021/ic900657w
     
  • Characterization of Self-assembled Metallodendrimers in Liquid and Gas Phase and at Air-Solid Interfaces
    H. T. Baytekin, M. Sahre, M. Engeser, A. Rang, A. Schulz, C. A. Schalley, Small 2008, 4, 1823-1834.
    DOI: 10.1002/smll.200800135
    highlighted in: Materials Views
     
  • Self-assembling squares with amino acid-decorated bipyridines: Heterochiral self-sorting of dynamically interconverting diasteromers
    A. Rang, M. Nieger, M. Engeser, A. Lützen, C.A. Schalley, Chem. Commun. 2008, 4789-4791.
    DOI: 10.1039/b806916f
     
  • Synthesis of Axially Chiral [4,4’]-Bipyridines and their Remarkably Selective Self-Assembly into Chiral Metallo-Supramolecular Squares
    A. Rang, M. Engeser, N.M. Maier, M. Nieger, W. Lindner, C.A. Schalley, Chem. Eur. J. 2008, 14, 3855-3859.
    DOI: 10.1002/chem.200800113
     
  • Self-assembly reactions between N-blocked metal corners (N-N)M(II) (N-N = ethylenediamine, 4,4'-substituted 2,2'-bipyridine; M = Pd, Pt) and the fluorinated edge 1,4-bis(4-pyridyl)tetrafluorobenzene
    M. Ferrer, A. Gutiérrez, M. Mounir, O. Rossell, E. Ruiz, A. Rang, M. Engeser, Inorg. Chem. 2007, 46, 3395-3406.
    DOI: 10.1021/ic062373s
     
  • Synthesis of Hydroxyl-functionalized N-Heterocyclic Carbene Gold(I) Complexes and Peptide Conjugates
    T. Diehl, M. T. S. Krause, S. Ueberlein, S. Becker, A. Trommer, G. Schnakenburg, M. Engeser, Dalton Trans. 2017, 46, 2988-2997.
    DOI: 10.1039/C6DT04834J
     
  • Stretch Out or Fold Back? Conformations of Dinuclear Gold(I) N-Heterocyclic Carbene Macrocycles
    S. Kobialka, C. Müller-Tautges, M. T. S. Schmidt, G. Schnakenburg, O. Holloczki, B. Kirchner, M. Engeser, Inorg. Chem. 2015, 54, 6100-6111.
    DOI: 10.1021/ic502751s
     
TRex
© FP

Charakterisation of Complex Samples,
Structure Elucidation, and Molecular Analysis in  Palaeontology

Sometimes it is a challenge to analyze a sample using mass spectrometry. We use HPLC-MS and nano-ESI, but our MALDI device is often the spectrometer of choice. It's about synthetic and bio-polymers, stubbornly MS-invisible lipids, molecules that are very sensitive to air and moisture, stinging hair juice from stinging nettles, and fossil samples:

As part of our subprojects A3 and M1 in the DFG-funded FOR 2685 Fossilization research group, we examine, among other things, dinosaur egg shells, bones and fossil wood.

Mass spectrometry is also suitable for obtaining information about the structure of new molecules and supramolecules. This is particularly important when the amounts of substances are not sufficient for NMR studies or the interpretation of the NMR spectra is not clear as is the case for parametric substances or averaged NMR signals due to rapid exchange processes. The classic method in this regard is the careful interpretation of EI spectra. For substances that require gentle ionization methods such as ESI and MALDI, structural clues can be found with the help of sophisticated experiments in tandem mass spectrometers. We follow more complicated fragmentation patterns in detail using multiple mass selection/fragmentation sequences. Another mass spectrometric means for structure elucidation is H/D exchange in the gas phase

    • Group 6 germylidyne complexes in the gas phase by LIFDI and APCI mass spectrometry
      L. R. Maurer, M. Engeser, Eur. J. Mass Spectrom. 2023, 29, 44-57.
      DOI: 10.1177/14690667221137465
       
    • Distribution, Ecology, Chemistry and Toxicology of Plant Stinging Hairs
      H.-J. Ensikat, H. Wessely, M. Engeser, M. Weigend, Toxins 2021, 13, 141.
      DOI: 10.3390/toxins13020141
       
    • Coordination of capsule assembly and cell wall biosynthesis in Staphylococcus aureus
      M. Rausch, J. Deisinger, H. Ulm, A. Müller, W. Li, P. Hardt, X. Wang, X. Li, M. Sylvester, M. Engeser, W. Vollmer, C. E. Müller, H. G. Sahl, J. C. Lee, T. Schneider, Nature Commun. 2019, 10, 1404.
      DOI: 10.1038/s41467-019-09356-x.
       
    • Styrene polymerization under ambient conditions using a transient 1,3,2-diazaphospholane-2-oxyl complex
      T. Heurich, Z. Qu, R. Kunzmann, G. Schnakenburg, M. Engeser, S. Nožinović, R. Streubel, Chem. Eur. J. 2018, 24, 6473-6478.
      DOI: 10.1002/chem.201800413

    • Identification and in vitro Analysis of the GatD/MurT Enzyme-Complex Catalyzing Lipid II Amidation in Staphylococcus aureus
      D. Münch, T. Roemer, M. Engeser, H.G. Sahl, T. Schneider, PLoS Pathogens 2012, 8, e1002509.
      DOI: 10.1371/journal.ppat.1002509
       
    • DNA-Based Phosphane Ligands
      M. Caprioara, R. Fiammengo, M. Engeser, A. Jäschke, Chem. Eur. J. 2007, 13, 2089-2095.
      DOI: 10.1002/chem.200601058
       
    • A Versatile Toolbox for Variable DNA Functionalization at High Density
      S. Jäger, G. Rasched, H. Kornreich-Leshem, M. Engeser, O. Thum, M. Famulok, J. Am. Chem. Soc. 2005, 127, 15071-15082.
      DOI: 10.1021/ja051725b

    • Light-induced formation of G-quadruplex DNA secondary structures
      G. Mayer, L. Kröck, V. Mikat, M. Engeser, A. Heckel, ChemBioChem, 2005, 6, 1966-1970.
      DOI: 10.1002/cbic.200500198

    • Mass Spectrometry as as Tool in Dendrimer Chemistry: From Self-Assembling Dendrimers to Dendrimer Gas-Phase Host-Guest Chemistry
      C. A. Schalley, B. Baytekin, H. T. Baytekin, M. Engeser, T. Felder, A. Rang, J. Phys. Org. Chem. 2006, 19, 479-490. DOI: 10.1002/poc.1105
    • Suberin, the hallmark constituent of bark, identified in a 45-million-year-old monkeyhair tree (Coumoxylon hartigii) from Geiseltal, Germany
      M. Tahoun, C. T. Gee, V. E. McCoy, M. Stoneman, V. Raicu, M. Engeser, C. E. Müller, Sci. Rep. 2024, 14, 118.
      DOI: 10.1038/s41598-023-50402-y
       
    • Molecular taphonomy of heme: Chemical degradation of hemin under presumed fossilization conditions
      M. Tahoun, M. Engeser, L. Svolacchia, P. M. Sander, C. E. Müller, Molecules 2023, 28, 4887.
      DOI: 10.3390/molecules28134887
       
    • Chemistry and analysis of organic compounds in dinosaurs
      M. Tahoun, M. Engeser, V. Namasivayam, P. M. Sander, C. E. Müller, Biology 2022, 11, 670.
      DOI: 10.3390/biology11050670
      Issue Cover Page
       
    • Dinosaur origin of egg color: oviraptors laid blue-green eggs
      J. Wiemann, T. Yang, P. N. Sander, M. Schneider, M. Engeser, S. Kath-Schorr, C. E. Müller, P. M. Sander, PeerJ 2017, 5:e3706.
      DOI: 10.7717/peerj.3706
       
    • Elucidation of the bridging pattern of the lantibiotic pseudomycoicidin
      K. Janssen, J. Krasenbrink, S. Strangfeld, S. Kroheck, M. Josten, M. Engeser, G. Bierbaum, ChemBioChem 2023, 24, e202200540.
      DOI: 10.1002/cbic.202200540
       
    • A Cholesterol Containing pH-Sensitive Bistable [2]Rotaxane
      M. Berg, S. Nozinovic, M. Engeser, A. Lützen, Eur. J. Org. Chem. 2015, 5966-5978.
      DOI: 10.1002/ejoc.201500657
       
    • Cleavage of Four Carbon-Carbon Bonds during Biosynthesis of the Griseorhodin A Spiroketal Pharmacophore
      Z. Yunt, K. Reinhardt, A. Li, M. Engeser, H.-M. Dahse, M. Gütschow, T. Bruhn, G. Bringmann, J. Piel, J. Am. Chem. Soc. 2009, 131, 2297-2305. DOI: 10.1021/ja807827k
       
    • Gas-phase H/D exchange of the protonated serine octamer cluster: "ion ping pong" of populations A and B
      U. Mazurek, M. Engeser, C. Lifshitz, Int. J. Mass Spectrom. 2006, 249/250, 473-476.
      DOI: 10.1016/j.ijms.2005.11.006
       
    • Mass Spectrometric Evidence for Catenanes and Rotaxanes from Negative-ESI FT‑ICR Tandem-MS-Experiments
      C. A. Schalley, P. Ghosh, M. Engeser, Int. J. Mass Spectrom. 2004, 232, 249-258.
      DOI: 10.1016/j.ijms.2004.02.003