Background
Solvents play a fundamental role in synthesis. Unfortunately, many commonly used volatile organic solvents (VOS) are harmful to humans and/or the environment. Some halogenated and polar aprotic solvents such as dimethylformamide, N-Methyl-2-pyrrolidone and 1,2-dichloroethane are already categorised as “substances of very high concern” under REACH. However, suitable alternatives are not yet available. The search for environmentally benign solvents is currently a hot topic in sustainable chemistry.
Recently, deep-eutectic solvents (DES) have emerged as novel reaction media. DES are related to ionic liquids (ILs) and usually composed predominantly of ions. They are often formed by combination of a quaternary ammonium salt (e.g. choline chloride, ChCl) with a hydrogen-bond donor (e.g. urea) to form eutectic mixtures. They have low vapour pressures, good thermal stabilities and are able to dissolve a range of solutes. As they are cheap, non-toxic, biodegradable, exhibit low volatility and are readily accessible synthetically from potentially renewable feedstocks they have many characteristics that make them desirable as potentially sustainable alternatives to VOS.
While DES have begun to be used as reaction media for transition-metal catalysis research is still needed to realise their potential. Our understanding of how solvation affects catalysis in DES is currently limited. This project aims to provide, for the first time, a detailed understanding of the role the complex solvation environment in DES plays in catalysis, through studies of hydrogen-transfer reactions where the team have experience. Complex, advanced NMR spectroscopy, alongside X-ray and neutron scattering experiments, will be used to realise this goal by exploring the structure and dynamics of the solvents and catalytic solutions in unprecedented detail.
Objectives
- To prepare and characterise a range of DES, including isotopically labelled compounds
- To undertake NMR studies to probe solvation of metal complexes in the DES
- To perform complementary total scattering measurements to probe liquid structure
- To study H2 activation and hydrogen-transfer catalysis in the DES and link the results to solvation
Experimental Approach
Selectively deuterated DES will be required for NMR and neutron-scattering experiments. This will leverage the expertise of both SBD and JMS in deuteration chemistry. Products will be characterised using NMR, IR, UV/Vis, MS etc. Advanced NMR studies will probe relaxation times, intramolecular spin-correlations and diffusion coefficients of various components within the DES, including dissolved catalysts e.g. RuCl2(PPh3)3. Complementary total scattering experiments (X-rays and neutrons) will also be performed. These studies will reveal information about the liquid structure of the DES, the local solvation environment around metal-containing solutes and dynamical information about various components in solution, including mass transfer. NMR experiments, including those with hyperpolarisation, will allow hydrogen activation and transfer reactions involving the metal catalysts to be studied. The results will be linked to the new understanding of solvation arising from the project to predict optimum catalyst operating conditions.
Novelty
Although metal-catalysed reactions have been reported in DES recently, there is little or no understanding of the role of the solvation environment around the metals on reaction outcomes in these complex liquids. This project will, for the first time, provide direct insights into the links between liquid structure and dynamics to metal-based reactivity and catalysis within DES.
Training
A broad training programme will equip the student with versatile skills. These include synthetic training in organic and organometallic chemistry, including deuteration studies and catalysis of high relevance to industry. Spectroscopic training will cover NMR, IR, UV/Vis, MS, including advanced multinuclear NMR spectroscopy and hyperpolarisation techniques. Experience will be gained of working at large national/international facilities. There is scope for students to use computational methods, such as DFT, to support experiments.
All Chemistry research students have access to our innovative Doctoral Training in Chemistry (iDTC): cohort-based training to support the development of scientific, transferable and employability skills: https://www.york.ac.uk/chemistry/postgraduate/training/idtc/
The Department of Chemistry holds an Athena SWAN Gold Award and is committed to supporting equality and diversity for all staff and students. The Department strives to provide a working environment which allows all staff and students to contribute fully, to flourish, and to excel: https://www.york.ac.uk/chemistry/ed/
For more information about the project, click on the supervisor's name above to email the supervisor. For more information about the application process or funding, please click on email institution
This PhD will formally start on 1 October 2023. Induction activities may start a few days earlier.
To apply for this project, submit an online PhD in Chemistry application: https://www.york.ac.uk/study/postgraduate/courses/apply?course=DRPCHESCHE3
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