A chemist and her children
Renana Gershoni-Poranne’s office is very spacious and tidy, but also quite personal. Hanging on the wall near her desk are drawings made for her by her boys, aged five and nine. One of them is in the style of Picasso, while the other is a charming copy of van Gogh’s sunflowers. Next to them is a brightly coloured footprint from her youngest son. “I love my office,” says the 35-year-old chemist. She sits behind her large corner desk and carries on chatting about the many birthday and holiday cards from colleagues that are displayed on a shelf on the other side of the room. Gershoni-Poranne talks so quickly, it’s difficult to get a word in.
The specialist in physical organic chemistry is one of six researchers to receive a Branco Weiss Fellowship award this summer. The research funding, worth half a million Swiss francs, gives the young researchers the opportunity to undertake ambitious and exceptional projects and to work on the topics they consider to be most important. Gershoni-Poranne’s project is also impressive: she wants to design novel organic compounds in order to equip electronic devices with improved, and perhaps also previously unimagined, functionalities.
The best compounds out of 1063 alternatives
Most modern electronic circuits and devices are based on silicon. However, this inorganic half metal presents limitations for developers regarding the efficiency of devices and the design of components. By contrast, electronics made from organic conductive polymers offer more potential, as their construction can be extremely thin, flexible and transparent. “Such materials allow us to produce devices capable of performing far more sophisticated tasks than at present,” Gershoni-Poranne says. Examples include displays on windowpanes that are still transparent enough to let through light. Or panes that absorb light during the day and then emit it again at night, acting like an indoor lamp. Or large surface solar panels wound onto rolls so they are much easier to transport than current solar cells made of silicon. On top of that, some organic components are biocompatible and could be fitted as biosensors that integrate with the human body. Organic components can also be biodegradable and therefore have a more positive impact on the environment.
The first products using organic electronics – such as foldable displays – are already available. Even so: “There are still so many potential chemical compounds we have not discovered and whose properties could be extremely useful,” Gershoni-Poranne says. Considering even a limited number of organic elements, such as carbon, oxygen, nitrogen and chlorine – and how they can be combined in small molecules – an unimaginably high number of compounds is theoretically possible: some estimates say 1063 in total, or to put it another way, a one followed by 63 zeroes. “If we only made 10 milligrams of each potential compound, it would still take more atoms than exist in the entire universe,” Gershoni-Poranne explains, providing some perspective, and notes that this is still just a portion of chemical space. Some, if not most, of the compounds that she aims to study and design are not even included in that estimate.
This means she conducts her research on a computer, rather than in the chemical laboratory, and uses computational techniques to characterize and analyse the behaviour of aromatic compounds. Molecules of this material class have a cyclic component with a special, overlapping distribution of electrons from the individual atoms. There are different types of such cyclic structures, and compounds that contain them enjoy special stability and the potential to conduct an electric current. This is why organic electronics consist mainly of aromatic-based molecules.
Little is known about which structural characteristics in aromatic compounds provide which functionality. That’s precisely what Gershoni-Poranne now wants to change. Her goal is to develop a system for “inverse design” of aromatic molecules. This approach involves making an initial decision on a substance’s desired properties and then working out which chemical structure is required. Gershoni-Poranne has already made good progress over the past few years, first as a postdoc at ETH and then working for two years as a senior scientist.
She gets up, walks around the desk and goes over to the wall by the door where there are a few posters displaying scientific results from recent years, including those of her students, whom Gershoni-Poranne affectionately calls her “academic children”.
She explains each one swiftly and concisely, while not forgetting to mention her collaborators on each project. Most recently, for example, she and her colleagues developed a model capable of predicting the properties of larger aromatic compounds based on smaller building blocks. In addition, she and her collaborators recently revealed a relationship between the aromatic nature of a compound and its HOMO-LUMO energy gap. This property concerns the energy of the electrons and is important for the potential efficiency of solar cells made of specific materials, for example.
Gershoni-Poranne is now keen to build on this work. Her aim is to develop a detailed database for aromatic compounds which combine the structure of molecules with their properties. The next stage will be to use this database for training special deep learning algorithms, known as generative models. These will in turn generate entirely new chemical compounds with specific predefined properties. “I have been thinking about and planning this project for about a year,” the chemist explains. The research grant provided by the Branco Weiss fellowship has allowed her to employ a doctoral student and get the project up and running.
Standing out in different ways
Given that Gershoni-Poranne seems to be in her element when engaged in research, it’s hard to imagine that she once contemplated a totally different career in music, as a soprano. “But only for a few seconds,” she says, laughing. During her military service she was a singer with the Israel Defense Forces Orchestra, she says, and gave many performances. And she was good! Later on, for example, she sang the Queen of the Night aria from Mozart’s Magic Flute at honorary doctor ceremonies. But it soon became clear to the US-Israeli dual citizen that without science, something would be missing from her life. “At the time I felt that I was not using part of my brain, and that was not a good thing for me.” Since then, singing is still an important part of her life and she still has regular singing lessons and performs occasionally.
Gershoni-Poranne is also involved in WiNS, a network devoted to increasing the representation of women in science. For example, WiNS organises workshops and seminars that focus on gender stereotypes or pass on tips on success factors for women in scientific careers. “Engaging in this field is important for me,” Gershoni-Poranne says, “as I believe it’s still tougher for women than for men to make a career in research and there are still far too few female professors.”
Nor was it easy for Gershoni-Poranne to combine scientific research with her family life. “When I was a postdoc, a colleague once told me I stood out because I was the only one with children.” But starting a family while still working on a doctorate was nothing out of the ordinary in Israel, because everyone – both male and female doctoral students – has to complete two to three years’ military service beforehand.
When she first started at ETH, however, she felt self-conscious when she had to leave at 4 o’clock to collect her children from nursery. She and her husband, also a researcher at ETH, take turns with childcare. “When he looks after the children, I can sometimes work on until 10 or 11 at night and on the weekends.” That sounds exhausting. “Yes, it is!” Gershoni-Poranne confirms. But she wouldn’t have it any other way. And she also thinks it’s good that she can be a role model for her two boys to show that a scientific career is not just the preserve of men and is happy that she and her husband can model for their children a dual-career lifestyle.
Finkelstein P, Gershoni-Poranne R. An Additivity Scheme for Aromaticity: The Heteroatom Case. ChemPhysChem (2019). doi: 10.1002/cphc.201900128
Gershoni-Poranne R, Rahalkar A, Stanger A. The predictive power of aromaticity: quantitative correlation between aromaticity and ionization potentials and HOMO–LUMO gaps in oligomers of benzene, pyrrole, furan, and thiophene. Physical Chemistry Chemical Physics (2018). doi: 10.1039/C8CP02162G