Universiteit Leiden

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Lezing

FRESH Lezing

  • Prof. dr. Sonja Herres Pawlis (Aachen University)
Datum
14 december 2017
Tijd
Bezoekadres
Science Campus
Einsteinweg 55
2333 CC Leiden
Zaal
GM4.13

Abstract

The majority of copper enzymes in biological systems directly activate dioxygen to perform a myriad of essential chemical transformations almost exclusively performed with copper. Tyrosinases (Ty), ubiquitously found in both eukaryotes and prokaryotes, are well recognized examples that perform the first committed step in the synthesis of melanine from tyrosine by catalytic hydroxylation of the phenol to a catechol by activating O2. Chemical model complexes extract the chemical reactivity of Ty to small molecules which allows a better investigation of structural variations and their influences on reactivity as well as the translation to industrially useful processes. 
As ligand systems, we use guanidines1,2 and bis(pyrazolyl)methanes3-7 in order to stabilize bis(µ-oxo) and peroxo complexes which are both discussed as active Ty species. In our ongoing studies, we developed versatile new ligands to explore new ways to the catalytic hydroxylation of various phenolates. We found that subtle changes in the ligand sphere have a dramatic influence on the stability of the Cu2O2 species as well as on its catalytic reactivity. Especially the donor difference between pyrazolyl and pyridinyl units is crucial to obtain the catalytic activity (Figure 1).6

Fig. 1: Four possible conformers of [Cu2O2{HC(3tBuPz)2(Py)}2]2+ and catalytic cycle

References

  1. S. Herres-Pawlis, R. Haase, P. Verma, A. Hoffmann, P. Kang, T. D. P. Stack, Eur. J. Inorg. Chem. 2015, 5426–5436.
  2. A. Hoffmann, M. Wern, T. Hoppe, M. Witte, R. Haase, P. Liebhäuser, J. Glatthaar, S. Herres-Pawlis, S. Schindler, Eur. J. Inorg. Chem. 2016, 4744–4751.
  3. A. Hoffmann, C. Citek, S. Binder, A. Goos, M. Rübhausen, O. Troeppner, I. Ivanović-Burmazović, E. C. Wasinger, T. D. P. Stack, S. Herres-Pawlis, Angew. Chem. Int. Ed. 2013,52, 5398-5401.
  4. A. Hoffmann, S. Herres-Pawlis, Chem. Commun. 2014, 50, 403-405.
  5. C. Wilfer, P. Liebhäuser, A. Hoffmann, H. Erdmann, O. Grossmann, L. Runtsch, E. Paffenholz, R. Schepper, R. Dick, M. Bauer, M. Dürr, I. Ivanovic-Burmazovic, S. Herres-Pawlis, Chem. Eur. J. 2015, 21, 17639 – 17649.
  6. A. Hoffmann, S. Herres-Pawlis, Phys. Chem. Chem. Phys. 2016, 18, 6430—6440.
  7. P. Liebhäuser, K. Keisers, A. Hoffmann, T. Schnappinger, I. Sommer, A. Thoma, C. Wilfer, R. Schoch, K. Stührenberg, M. Bauer, M. Dürr, I. Ivanović-Burmazović, S. Herres-Pawlis, Chem. Eur. J. 2017, 23, 12171-12183.

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