Theoretical studies of actinide complexation with macrocyclic ligands: identifying synthetic targets and real-world applications

I propose to investigate the chemical interaction between uranyl and a series of porphyrins. Uranyl is an oxygen complex of the heavy element uranium and porphyrins are large, ringlike carbon-based molecules. Several of these chemical complexes have been created in laboratories, and I envisage the results of my research having applications as diverse as nuclear fuel enrichment, radiation detection, cancer therapy, and solar energy. In addition, my work will identify complexes that research chemists should focus their efforts on synthesising in the laboratory as well as demonstrating that state-of-the-art theoretical methods can and must be applied to these complexes in order to give a quantitative understanding of their chemical structure.

The porphyrins can be considered as molecular rings, or macrocycles, with a central cavity in which other atoms and molecules can reside, and the variety of applications I have suggested is possible since they can be easily modified in order to change their properties:

-Their size can be altered, so that they can be tailored to 'fit' with uranyl to varying degrees.
-They can be modified so that they evaporate more readily when heated.
-Related macrocycles enable one to choose the type of atom with which the uranyl directly interacts.
-They can be altered so that the strength with which they bind uranyl can be varied.

An important part of my proposed work is that it is computational: all of my direct research will be via simulation. Simulation plays a greater role in research into the actinide series of elements, which includes uranium, than in other areas of chemistry, since all actinides are radioactive, some of them extremely so, and there are very few facilities in the world where chemists can work with them. This means that less laboratory work can be performed, and so accurate simulation is a requirement in order to further our understanding of these elements.
My proposed research employs extremely sophisticated theoretical techniques in order to study uranyl porphyrin complexes. Whilst there has been some previous simulation work on such complexes, it has been carried out using less accurate methods. The realisation of the potential applications that I have outlined are dependent on specific details of the interactions between the porphyrins and the uranyl. Such details are often unavailable directly from experiment; theoretical techniques with strong predictive capabilities are therefore a necessity. In my previous research I have shown that popular theoretical methods may not be capable of even qualitative descriptions of actinide complexes, particularly for the heavier actinides such as plutonium, and it is only in the present day that computational resources are available to conduct simulations capable of quantitative predictions on such relatively large complexes.

As part of my proposed research I also intend to study the interactions of the porphyrins with other actinide elements. Other actinides can behave very differently to uranium, and understanding when and how they differ are fundamental questions in heavy element chemistry. The properties of the porphyrins that I have described allow many different aspects of these fundamental questions to be considered.

In summary, the significant theoretical study that I propose here will complement the excellent experimental work being carried out both in universities and national laboratories in the United States. Whilst the primary goal of this work is the realisation of the applications I have outlined, it will also set new standards in the simulation of large molecular systems, and deepen our understanding of the chemistry of the actinide series.

Who will benefit?

1) Nuclear industry professionals.

2) Current academic researchers.

3) The next generation of researchers, both academic and industrial.

4) Society as a whole, through knowledge advancement and economic benefit.

5) The public, through the raising of awareness of key issues with regard to the continuing adoption of nuclear power facilities.

How will they benefit?

1) My contact with the nuclear industry so far leads me to conclude that there is significant scope
to enhance the role played by computational. I will directly approach contacts I am already making with representatives in this industry in order to gain opportunities to speak at seminars and workshops, where I can emphasise the role that theory can play. I will demonstrate that theoretical studies can bypass the difficulties associated with experimental work on these highly radioactive, difficult to handle materials, and so streamline the process of obtaining solutions to nuclear waste management problems. In this way I intend to change the perception of theoretical chemistry in industry, leading to more widespread acceptance and a change in working habits that can only have a beneficial impact, both from a knowledge transfer and economic perspective, in the long term.

2) My research will produce scientific advances in both methodology and novel analysis. This will impact directly on the fields of fundamental f-element chemistry and synthetic chemistry, as well as providing novel links between the two. Successful fulfilment of my objectives may also lead to a novel experimental probe of aromaticity, and a novel theoretical interpretation of oxidation state. If my results support my hypotheses regarding applications, new avenues of research and potential collaborations with workers in less related fields such as healthcare and alternative energy will be created.

3) Doctoral training centres such as the EPSRC funded 'Nuclear FiRST' focus on training postgraduate students for the nuclear industry, and the EU FP7 ACTINET-I3 theoretical user lab runs PhD schools. I intend to give lectures based on my research at both in order to introduce the next generation of researchers to the benefits of applying theoretical chemistry to nuclear-relevant systems. I am also active within the Thomas Young Centre (TYC), an interdisciplinary community of London research groups, which holds numerous informal events such as coffee mornings and soirees, and I will take advantage of these to ensure my ideas and approaches are communicated to the next generation of researchers.

4) The intended consequence of my interactions with nuclear industry is the streamlining of processes leading to solutions of problems in nuclear waste management. Any advantage that can be gained through the utilisation of theoretical methods will present a significant reduction in cost and time, and will therefore be of direct economic benefit to society. I will also engage with UCL Business PLC, to explore any commercial exploitation that could be achieved from my research. Such exploitation would have a clear economic benefit to the UK, given the prevailing positive attitude to nuclear power across many developed nations at the current time.

5) There is currently significant public interest in issues surrounding nuclear power, which means that there are numerous opportunities for raising public awareness of these issues. I will engage with the public through lectures, exhibitions, and science fairs. This will serve two purposes. Firstly, it will give me the opportunity to deal with issues regarding the lack of public trust in nuclear power, which is partially due to a lack of dialogue between experts and the layperson. Secondly, I can emphasise the role theory has to play in the development of technology, since I believe this to be something that the public is largely unaware of.