Speakers

Biomimetics on Small Molecule Activation

Jaeheung Cho
Jaeheung Cho
DGIST, Korea
16:30~17:15, November 20th, 2014

Abstract :

Small molecule activation by transition metal centers is essential to numerous stoichiometric and catalytic organic transformations in biological and industrial processes. Nature has gone through a course of trial and error to refine the living creatures, processes, and materials over 3.6 billion years. Oxygen-coordinating metal intermediates, such as metal–superoxo, –peroxo, –hydroperoxo, and –oxo species, are frequently invoked as plausible oxidants in the oxidation of organic substrates in the living organisms.[1] Here, we describe our recent results on the synthesis, structural and spectroscopic characterization, and reactivity studies of M-O2 complexes bearing tetraazamacrocyclic n-TMC ligands, where M = Cr, Mn, Fe, Co, and Ni and n = 12, 13, and 14.[1,2] Notably, several novel metal-O2 complexes, demonstrated by x-ray crystal structures to be end-on metal-superoxo and side-on metal-peroxo species, have been thoroughly characterized using various spectroscopic techniques, including resonance Raman and x-ray absorption spectroscopy. The metal ions and the ring size of the supporting ligands are found to be important factors that control the geometric and electronic structures of the metal-O2 complexes (i.e., end-on metal-superoxo vs. side-on metal-peroxo). Reactivity studies performed with the metal-superoxo and -peroxo complexes reveal that the former is capable of conducting electrophilic reactions (e.g., oxygen atom transfer and C-H bond activation of organic substrates), whereas the latter is an active oxidant in nucleophilic reactions (e.g., aldehyde deformylation). A complete intermolecular O2-tranfer from metal(III)-peroxo complexes to a Mn(II) complex has been demonstrated as well.

 

[1] J. Cho, S. Jeon, S. A. Wilson, L. V. Liu, E. A. Kang, J. J. Braymer, M. H. Lim, B. Hedman, K. O. Hodgson, J. S. Valentine, E. I. Solomon, W. Nam, Nature 2011, 478, 502-505.
[2] J. Cho, R. Sarangi, W. Nam, Acc. Chem. Res. 2012, 45, 1321-1330.

 

Research Interests

  • Design of model complexes of metalloenzymes
  • Characterization and reactivity studies for biomimetic materials
  • Application for medical and environmental materials

 

Awards and Honors

  • 2014 : Co-chair (symposium), The 41st International Coordination Chemistry Conference
  • 2013 : Co-chair, International Symposium on Bioinorganic Chemistry
  • 2010 : The Distinguished Lectureship Award from the Chemical Society of Japan
  • 2008 : Organizing Committee Member, The 4th Asian Biological Inorganic Chemistry Conference