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September/October 2019

Making molecular switches

Late last year, Dr Suzanne Neville – a lecturer and researcher in the University of New South Wales’s School of Chemistry – received the prestigious Sandy Mathieson Medal, an award for distinguished contributions to science involving X-ray, neutron or electron diffraction/imaging by a researcher under 40 years of age. Lachlan Gilbert talks to her about the work that led to this recognition.  


Your work sounds very specialised – what exactly is it that you study?

My work is focused on making new materials called molecular switches. A molecular switch is a molecule that can exist in two (or more) different states that can interchange in response to environment stimuli, such as temperature, pH, light and pressure. In molecular switches, the distinct states show distinct properties and for this reason they are of interest in the field of nanotechnology for molecular computers in which the components are small (i.e. built up from individual atoms and molecules), rather than being manufactured as small devices.


What is the state of this technology today?

In some cases, the molecular switches can be used to produce controlled molecular motion – this is a simple example of a molecular machine. In fact, a Nobel Prize for such work was awarded in 2016. In the majority of work on molecular machines (and molecular switches), the switching between different states occurs with the molecules in solution.

My work looks at making molecular switches that function as solid crystalline materials. This is a particularly challenging task because initiating and controlling the motion of solids is less favourable than in solution. But if successful, it will allow controlling the properties of materials at the molecular level to be achieved in a more orderly fashion and bring us a step closer to molecule-based memory devices.


What was it in particular about your work that led to you being awarded the Sandy Mathieson Medal?

My research on molecular switching materials intrinsically relies on knowing and understanding the structure of the different states and this is obtained by using a range of X-ray diffraction techniques. Such structural information helps us understand the properties of each material and collectively build up a broader understanding of what structural features we can manipulate to make our properties even better in the future.

We typically use temperature change to induce the switching between states, but have also successfully used pressure changes, light irradiation and change of solvent molecules to trigger the molecular switching. One of the biggest reasons I was awarded this medal is that these types of experiments are non-standard and have involved extensive equipment and method development over the last 15 years, including novel techniques using synchrotron radiation. I also received this award because my work uses a non-typical combination of crystallographic techniques that I apply to every new material to develop a more comprehensive view of the structure dynamics that occur before, during and after the molecular switching event. Both of these aspects are now used as a standard around the world.

In recognition of Sandy Mathieson’s contributions to crystallography, the Sandy Mathieson Medal is awarded to a researcher under the age of 40 for distinguished contributions to science involving crystallography. This medal is awarded by the Society of Crystallographers of Australia and New Zealand (SCANZ). I am very grateful and humbled to receive the award, in particular given that the award is interdisciplinary because crystallography is used across chemical, biological and materials sciences.


The award is given to someone who’s under 40, so you’ve achieved quite a bit at a young age, haven’t you?

I’m glad to hear that 40 is a young age! But in all honesty, I think rather than being an age-related achievement, I am prouder of doing so while being the primary carer of two young children (4 and 8 years old) – it has been a substantial challenge to maintain momentum with two maternity leave breaks. In fact, one of my long-term goals is to use my experience to inspire more females to continue on an academic career path.


Can you tell me about any upcoming projects?

In the past we have travelled overseas to the Advanced Photon Source synchrotron facility in Illinois, USA, to conduct in situ crystallography experiments. Recently, we have been working closely with the Australian Synchrotron and ANSTO to develop the same types of experimental set-ups in Australia. This will be a big time and cost advantage for us, and what we develop will be useful for many other Australian researchers. We have some promising results so far. We also have plans in the near future to develop some new methods so that we can make movies of the dynamic structure changes that occur over the molecular switching process – this will be both a great teaching tool and an excellent visualisation tool to understand the properties better.


What about on the research side of things?

We have been working on a new exciting avenue of molecular switches that are embedded in porous materials. These materials can be used as molecular sensors as the switching can be turned ‘on’ or ‘off’ depending on what molecules are in the pores, or the particular characteristics of the pore contents can be used to tune the molecular switching properties. This is a powerful tool. This is not novel in itself, but what we are doing within the pores is. We have been looking at using the breathing motion within the pores, which occurs over the molecular switching process to manipulate position and chemistry of the encapsulated molecules – this is a big challenge and we have made some good progress. Why would we want to do this? We want to mimic what nature does, for example, in ribosomes, by precisely positioning simple molecules and then doing chemistry on them to make more complex molecules.

Lachlan Gilbert is media adviser, UNSW Sydney’s Media & Content team for the STEMM faculties.

Reprinted (adapted) with permission from Murphy J.M. et al. Guest programmable multistep spin crossover in a porous 2-D Hofmann-type material, J. Am. Chem. Soc. 2017, vol. 139(3), pp. 1330–5. Copyright 2017 American Chemical Society.

The pores in this material can be used to expand the molecular switching to have two (1-step), three (2-step) or four (3-step) stable states that are accessible by temperature change.

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