12.04.2016 - Özlen Ferruh Erdem : ESR characterization of hydrogen-producing bioinspired inorganic catalysts

ESR characterization of hydrogen-producing bioinspired inorganic catalysts

Özlen Ferruh Erdem
Department of Physics, Middle East Technical University
12 April 2016, Tuesday, 14:40
Cavid Erginsoy Seminar Room, Physics Department, 3rd floor

Abstract: Many microorganisms use molecular hydrogen as an energy source (H2 uptake) or protons as an electron sink (H2 evolution) via the hydrogen conversion redox reaction that is catalyzed by hydrogenases. Inspired from nature, synthetic catalysts which mimic the function of the active site of [FeFe] hydrogenases have been developed.¹ Complexes which accommodate mononuclear iron(I-III) intermediates that feature hydride, phosphine, cyclopentadienyl, and pendant base ligands are of special interest. By means of a theory-supported spectroscopic approach (with FT-IR, EPR, Moessbauer, as well as DFT), it will be shown that not only the metal-core and direct ligands, but also the second coordination sphere have influence on the catalytic activity. It will be presented that for an iron hydrido catalyst, the catalytic direction of this class of monoiron compounds can be reversed by rational design of the ligands.² Investigation of trapped intermediates in their diamagnetic and paramagnetic states provides a comprehensive understanding³ of the working principles of natural enzymes and bioinspired model compounds, and leads to newly designed, highly efficient catalysts.

References:
1. Erdem et al., "A model of the [FeFe] hydrogenase active site with a biologically relevant azadithiolate bridge: a spectroscopic and theoretical investigation“, Angew. Chem. Int. Ed. 50 (2011) 1439.; Hsieh et al., “Redox active iron nitrosyl units in proton reduction electrocatalysis”, Nature Comm. (2014) doi:10.1038/ncomms4684; Erdem et al., “Effect of cyanide ligands on the electronic structure of [FeFe] hydrogenase active site model complexes with an azadithiolate co-factor”, Chem. Eur. J. 19 (2013) 14566.; Karnahl et al., “Mixed-valence Fe(II)Fe(I) hydrogenase active site model complexes stabilized by a bidentate carborane bis-phosphine ligand”, Dalton Trans. 41 (2012) 12468.
2. Weber et al., “Design and characterization of phosphine iron hydrides: towards hydrogen-producing catalysts”, Inorg. Chem. 54 (2015) 6928.
3. Lunsford et al., “Cyanide-bridged iron complexes as biomimetics of tri-iron arrangements in maturases of the H cluster of the diiron hydrogenase”, Chemical Science (2016) accepted.

Reminder: Tea and cookies will be in the seminar room before the seminar.