Understanding the [Fe Fe]-Hydrogenase H-Cluster: Insights From Chemical Modelling and Advanced Spectroscopy

Hydrogenase enzymes are nature’s catalysts for hydrogen production and uptake. Understanding how they work may lead to new materials as alternatives for precious metals currently used in H2-utilizing fuel and producer cells. Work described in this thesis focuses on synthetic mimics of the active site of [Fe Fe]-hydrogenases and explores their reactivity towards protons and electrons. Chapter 1 gives a brief overview of the chemistry taking place in hydogenase enzymes with a particular focus on the [Fe Fe]-hydrogenase. The evolution of synthetic models mimicking the structure and function of the enzyme from the late 1990s to the current state of the art is discussed. Chapter 2 describes synthesis of the first {2Fe3S} hydride together with new active site mimics in which bulky substituents are incorporated into the dithiolate bridgehead. A comprehensive examination of their structural features and spectroscopic properties is provided. Chapter 3 reports extensive stopped-flow UV-vis, IR and electrochemical studies for a range of subsite models exploring the relationship between the structure and the reactivity towards protons. It is shown that there is a direct linear free energy relationship between the activation energy for protonation and the energy level of the HOMO. Chapter 4 describes the first characterisation of paramagnetic (mixed-valence) Fe(I)(μ-H)- Fe(II) species which is implicated in metallo-sulfur enzymes as an intermediate in electrocatalytic H2 evolution. An unprecedented super reduced state is detected and characterised using a custom-built spectroelectrochemical cell.Chapter 5 shows how muon spectroscopy may provide a new approach for exploring metallo-hydride chemistry. Future avenues of research in the field of [Fe Fe] chemistry arising from the work described in this thesis are also briefly discussed.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2014

Author dc:creator

• Jablonskyte, Ausra

Language dc:language

en