Penny Brothers tells Michael Brown about porphyrins, the porphyrin-boron mismatch and their potential role in neutron capture therapy

Penny Brothers is an associate professor at the University of Auckland. Her research brings together her interests in porphyrin chemistry, the main group elements and organometallic chemistry. She investigates how the porphyrin ligand can be used to modify the chemistry of elements such as boron and bismuth.  She has recently begun to explore the chemistry of main group elements with the related macrocycle corrole.

 

What motivated you to specialise in organometallics and porphyrins?
At the University of Auckland, where my father was a geology professor, there were display cases full of minerals that I loved looking at.  All the beautiful crystals, with all their different morphologies and colours, helped attract me to inorganic chemistry.  When I was choosing my masters research subject area, Professor Warren Roper, an organometallic chemist, was my mentor. 

His lectures really appealed to me at the time. Organometallic chemistry was an area that was expanding rapidly and I was enthused by the idea of working at the interface between the traditional disciplines of inorganic and organic chemistry.  

Warren Roper had a long association with Jim Collman and I went to Stanford to do a PhD in his group, which was focused on porphyrin chemistry. I worked on a porphyrin project, which I enjoyed, and that was how I got into porphyrin chemistry. I have been there ever since.

Who do you admire most in science?
I admire the scientists who were doing really difficult synthetic chemistry 100 years ago.  The one I tell my students about is Alfred Stock, who did a lot of early borane chemistry on compounds that are horrendously difficult to handle as they are pyrophoric and toxic.  These scientists were investigating very labile compounds before anyone actually knew what the structure of the atom was, and before there were any good models of a chemical bond; yet they were doing really difficult synthetic chemistry with very limited analytical tools.  Those are the people that I really admire because in terms of the theoretical framework, they didn't have what we have now. However, in terms of their actual hardcore, practical skills of manipulation and observation, they are probably unmatched.

Can you explain the significance of your work?
Boron-porphyrin chemistry is where my attention is at present.  In terms of significance there are potential applications of boron porphyrins in sugar sensing and in neutron capture therapy. Porphyrins are known to localise on the surface of a tumour and the boron serves as the neutron capture element.  Others have investigated boron attached to the periphery of the porphyrin, but my research involves boron coordinated to the centre of the porphyrin.  In coordination chemistry, a ligand is often designed for a specific coordination geometry and metal centre, producing a thermodynamically stable complex.  In our research, we do the reverse. Porphyrins are a total mismatch for boron, with the wrong coordination geometry and the wrong size, and this mismatch can stimulate some unusual and interesting chemistry. This fundamental interest is my main motivation. 

By using a ligand, element or combination that is not a good match, you stress things and make them uncomfortable and this results in unusual reactivity.  My research with boron and porphyrins works well enough that you can make complexes that are stable enough to isolate and characterise.  I also feel very strongly that there is a big push towards focusing on the applications of chemistry at the expense of continuing to allow our curiosity to drive us into completely new areas of chemistry.  In fact, if you look at where a lot of chemical applications come from and what applied chemistry draws on, it is the huge database of fundamental chemistry generated by people driven by intellectual curiosity and passion.  Without that database, there wouldn't be the resources that you need to make more focused applications. I see myself as contributing to that fundamental knowledge. 

What are the advantages of collaborations and have they been beneficial?
Absolutely. Students view chemistry as something rather dry that you read about in text books and journal articles.  If you can show students the link between the research and the people that are committed to chemistry, then it becomes more interesting and easier to understand. I think chemistry becomes more alive and a richer subject when you know the people that are involved in it.  When you read the work of someone you know personally, you can find it easier to understand because chemists, like anybody else involved in creative endeavours, express their personalities through their work.  We have no hesitation in understanding this for artists and musicians, but it is also true in science. With collaborations, you not only get the experience of someone else's expertise, you get their intellectual input, and a personal interaction that means it becomes the creative endeavour of a bigger team. 

Did you face any challenges as a woman in science?
Because I grew up in a household of scientists, I never felt I had a barrier, either as an individual or as a woman, to overcome.  I had a lot of support from my family, teachers, mentors and advisors, so I had a very straightforward pathway through the system. Women often have a more difficult journey into an academic career, as they may have family responsibilities or may have to fit with the career plans of a partner. For my generation in particular, the career aspirations of women began to be valued for the first time, so I was very lucky to start my career at the time I did.  I have never encountered any overt discrimination, but I do recognise that there are barriers in the system.  I think that we often generate some of the barriers ourselves and women can lack the confidence to strive for their goals. 

At the moment there are equal numbers of male and female students right up to PhD level but there is still a big fall-off of women going into academic positions. Although there has been a lot written on the subject, it's still hard to pinpoint the reasons for this.  I have always focused on trying to strive for achievements that stand on their own merit.  I have never wanted to be given credit or get by with a lower standard because I am a woman and I think that is very important, but by the same token, I do think it sometimes does help being a woman and in a relative minority as you may get noticed or recognised because you are different.  I have been lucky to have a very supportive husband. He is also an academic chemist and he works at the same institution as me. We have separate research interests, but we have always run a joint research group so that when I took short periods of parental leave, it was very beneficial. It was a smooth transition because he was able to co-supervise students and bring news home every day so I didn't go through a period of professional isolation when I had young children.

What do you enjoy most about your role on the Chemical Communications editorial board?
The more diverse the network of people I know in the world of chemistry, the more I enjoy it.  When I was appointed to the editorial board, my first reaction was to think that I need to get over my lack of confidence. I can make as much of a contribution to the editorial board as anyone else. Particularly, I can add a perspective from a smaller country that is outside the big hubs of activity like the US, the UK, Europe and Asia.  I have always been interested in publishing, but felt that it was inevitable to end up in an academic position as I grew up in that environment. If I hadn't ended up doing academic chemistry, I would have liked to be involved in science publishing, so this is a really good opportunity for me to learn a bit more about that and make a contribution to a different area.  

What do you do in your spare time?
To me, having a balanced and varied life is very important. The three most important areas are my family, my work and the activities that add value to my life and involve me in other circles of friends.  I swim regularly and do quite a lot of running.  I ran the New York marathon last year and in the last few years, I have been enjoying long distance mountain running.  The longest run that I have done is 60 kilometres and the longest continuous event I have done is 100 kilometres.  I have developed good friendships with women in demanding professional jobs like mine, and once a year we go on a hiking trip to challenge ourselves in something outside of work. I also enjoy orienteering because it has an intellectual problem-solving side to it as well as the exercise, and all of these things keep me physically fit.  I balance the sports by singing with Auckland Choral. The balance of activities in my life is really important; I strive to maintain it, so I don't let work pressures crowd out those other things. I think, ultimately, what you achieve at work is never going to be as satisfying as what you achieve in the whole of your life.