Harnessing Dithiolene Complexes for Carbon Dioxide Activation

Furney, Isaac (2025) Harnessing Dithiolene Complexes for Carbon Dioxide Activation. Doctoral thesis, University of East Anglia.

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Abstract

Molybdenum and tungsten are found in the active site of a number of metalloenzymes. Bound to these atoms are sulphide-containing ligands, more commonly referred to in the literature as dithiolene ligands. The combination of metal and ligand allows for catalysis close to the thermodynamic limit of carbon dioxide reduction to formate to take place. Thus, these active sites are attractive targets for chemists, as their potential for industrial application is limitless.

This thesis focuses on the synthesis of mimics of the active site of the formate dehydrogenase enzyme (FDH). By providing functional models of the active site, we wish to identify the necessity of proton relays in close proximity to the central metal ion for catalysis; their presence is seen in the native enzyme, but is missing from the catalytically-competent models in the literature.

A route to a novel molybdenum-oxo bis-dithiolene complex was successfully created, streamlined and improved by previous researchers within the group. This novel route was then used to generate more ligands and subsequent complexes in an effort to showcase the versatility of the synthesis. The terminal functionality of the FDH active site is not limited to just oxo ligands, but to other elements in Group 18 such as sulphur and selenium. Attempts at synthesising the sulphido analogue of the target complex were made, but unfortunately this was unsuccessful. A ‘third generation’ pro-ligand was also synthesised with the goal of creating novel, bridged molybdenum-oxo dithiolene complexes. Unfortunately, attempts to synthesise this new kind of dithiolene complex were unsuccessful. The synthesis of the tungsten analogues of these compounds was explored but merely added to the reputation of the difficulty in working with tungsten compounds; fortunately, the tungsten analogue of the target complex was synthesised for a time, and key data points were recorded.

Computational methods were employed to better understand the physical properties of the synthesised complexes, with a focus on the accurate prediction of the infrared stretching band of the Mo O bond. This process of identifying this stretch was aided by the use of five functionals, each with varying constraints. The functionals that achieved the most accurate predictions can now be reused as a standard for other researchers to conduct computational studies on molybdenumoxo dithiolene complexes with a high degree of certainty in the accuracy of their results. The importance of electrochemical methods for understanding the behaviour of redox-active metals cannot be understated. Several of the synthesised complexes were subjected to cyclic voltammetry, allowing structure-activity relationships to be derived for the MoIV/MoV and MoV/MoVI redox couples.

The target complex and its non-functionalised analogue were tested for their catalytic activity with the goal of seeing the catalytic reduction of carbon dioxide into formate. Although the results for the reduction of carbon dioxide to formate and oxygen atom transfer catalysis were poor, oxidation catalysis of formate showed that the complexes were four times more effective with the proton relays than without.

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Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
Depositing User:	Kitty Laine
Date Deposited:	04 Nov 2025 13:49
Last Modified:	04 Nov 2025 13:49
URI:	https://ueaeprints.uea.ac.uk/id/eprint/100896
DOI:

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