Designing Highly Axial Lanthanide Single Molecule Magnets

For over fifty years economic factors have driven a steady trend of making electronic devices smaller. However, the rate of progress in miniaturisation has started to stall, and it has been predicted that a plateau may be reached within ten years. As such, "bottom-up" alternatives are sought to rival the current "top-down" approach to ensure continued technological advancement. One promising solution for high-density data storage is to use Single Molecule Magnets (SMMs). These are molecules that can store magnetic information, and could therefore give the smallest possible devices.

Lanthanide (Ln) SMMs have emerged as leading candidates due to their favourable magnetic properties, but at present these only function with expensive liquid helium cooling. The temperatures at which Ln SMMs retain magnetic information are dictated by the choice of Ln, the molecular geometry, and the competition of magnetic relaxation pathways. These factors can all potentially be controlled but at present the relaxation mechanisms are still poorly understood. Relaxation processes can significantly lower the temperature at which magnetic information is retained, based on what would be predicted solely from consideration of a specific Ln with a well-defined geometry.

As such, the syntheses of Ln SMMs with ideal metal/geometry arrangements are targeted, as these will give the maximum thermal barrier to magnetic relaxation. Once control of molecular geometry and optimal barriers are obtained, the magnetic relaxation pathways of these systems can be studied in depth over a large temperature range. Such a study has not previously been attempted on Ln SMMs. This will allow us to deepen our understanding of the factors dictating relaxation mechanisms, so that in future we can design Ln SMMs that disfavour such processes and can store magnetic information at even higher temperatures.

It has been predicted by calculations that dysprosium(III) SMMs with only two donor atoms set opposite to each other (a two-coordinate, perfectly axial environment) will give the largest barriers to thermal magnetic relaxation. These systems could operate above liquid nitrogen temperatures, at which point they would become technologically viable. Ln ions prefer high coordination numbers and two-coordinate Ln(III) complexes are currently unknown, hence this would be a remarkable synthetic achievement.

In recent work, we have reported a six-coordinate Dy(III) SMM with an environment that effectively mimics the axial system we seek, and yielded a world-record barrier to magnetic relaxation (Chemical Science, 2016, 7, 155). We have made theoretical predictions for improvements to the design of this system to raise this barrier even further, and have set out synthetic routes to achieve this goal in this proposal. More ambitiously, we target the synthesis of chemically feasible two-coordinate Dy(III) SMMs, following our predictions that these could exhibit magnetic relaxation above liquid nitrogen temperatures (Inorganic Chemistry, 2015, 54, 2097). We have recently reported the synthesis of a rare two-coordinate Ln(II) complex with a near-linear geometry (Chemical Communications, 2015, 7, 155), hence we are in an ideal position to transfer these methodologies and prepare the first two-coordinate Dy(III) SMMs.

All synthetic studies in this proposal will be complemented by high level physical analysis of magnetic and electronic properties, including computational modelling. This will provide essential information to guide our pioneering studies of magnetic relaxation pathways and their relationship to the geometry and electronic structure of Ln SMMs. Ideally we may synthesise a Dy(III) SMM that can operate at liquid nitrogen temperatures.

The PI and CIs have strong track records in delivering impact through their outputs and have established significant collaborations. We align with key EPSRC themes and priority areas and we will deliver:

1. A deeper understanding of f-element chemistry and magnetic relaxation pathways.
2. Results that are of both academic and future technological benefit.
3. Early career researchers with a unique sets of skills that benefit the UK economy.
4. Significant outreach activities to communicate this work to the public.

The Pathways to Impact document describes our strategy to maximise the impact of our work on economy, society, knowledge and people. We use a variety of activities to engage with the public and private sectors, academia and the public, with well-defined timescales and milestones.

Outreach: The PI and CIs have a proven track record of public outreach activities. For example, the PI has: i) received formal outreach training; ii) performed school visits to deliver live experiments; iii) had an active role in delivering a series of public lectures at the 2012 Royal Society Summer Science Exhibition; iv) been a consultant for BBC Worldwide, designing and planning experiments; and, v) contributed to the Nuclear Hitchhiker blog, communicating issues involving nuclear energy. We will build on these activities during this project by setting up a dedicated f-element stand at the annual Manchester Science Festival and building new web content to further publicise this work. Our group members will also be involved in regular outreach activities organised by the School of Chemistry involving schools and sixth-form colleges, including lectures, workshops and laboratory classes to engage a considerable number of pupils, teachers and parents.

Industry and Commerce: In a best case scenario we could access single molecule magnets (SMMs) that can store data at liquid nitrogen temperatures. This would make SMM storage devices technologically viable for the first time. Although potential economic impact is expected outside the timescale of this grant application, mechanisms are already in place at Manchester to achieve this, including industrial knowledge transfer partnerships. The University of Manchester Intellectual Property Company (UMIP) provides a free and easy to access service to discuss potential commercialisation opportunities at an early stage of development. Following identification of commercial potential, UMIP can provide proof-of-concept funding to allow a short-term PDRA (e.g. 6-12 months) to shape potential industrial scale-up and patent applications. Following intellectual property protection, UMIP will assist with marketing products to industry.

Training: The two PDRAs will be part of a multidisciplinary team involving four research groups. As such they will receive skills and training that are unique to this project that will give them an excellent foundation upon which to build their future careers. The synthetic PDRA will gain the rare ability to handle highly air sensitive f-element complexes, recently highlighted as a major skills shortage by government and the nuclear and fine chemical industries. The physical studies PDRA will gain a unique set of skills in the analysis and interpretation of f-element magnetic and spectroscopic data, coupled with the rare ability to perform high level ab initio calculations. These proficiencies would also be of use for the nuclear industry for the modelling of waste streams and internuclear separations. The PDRAs will be actively encouraged to design and to implement their own strands of research and to prepare manuscripts for publication to give them the best possible chance of success in pursuing a career in academia or in industry. Transferable and general skills will also be developed in tandem to make group members highly employable in other career paths.