Readers pay tribute to Rudolf Zahradník, and share memories of colourful chemistry and investigating the persistence of pesticides

Rudolf Zahradník (1928–2020)

The pioneering quantum chemist and founding president of the Czech Academy of Sciences and the Learned Society of the Czech Republic, Rudolf Zahradník, died on 31 October 2020 in Prague.

Joining forces with Jaroslav Koutecký, Zahradník laid the foundations in the 1950s and 1960s of what is known as the Prague school of quantum chemistry. Despite Koutecký and his key associates, Joe Paldus and Jiří Čížek, emigrating in the aftermath of the Soviet-led invasion of Czechoslovakia in 1968, the Prague school continued to prosper throughout the politically and materially adverse 1970s and 1980s. In the wake of the Velvet Revolution, Zahradník was elected director of the Heyrovský Institute in 1990. The list of problems tackled by Zahradník and his circle of students and collaborators included the electronic structure and spectra of alternant and non-alternant hydrocarbons, the structure and properties of open-shell systems, weak molecule–molecule interactions, catalysis, interactions of biomolecules and ion–molecule reactions. Charles Coulson’s plea to theorists to ‘give us insight, not numbers!’ might have as well come from Zahradník.

Interestingly, and perhaps characteristically, Zahradník would designate the fall of Nazism and then of Communism as the greatest moments of his life. He would often compare the ways these two regimes treated culture in general and academia in particular. Neither proved capable of extinguishing Zahradník’s enthusiasm for science or of precluding him from doing what was right. In the words of physical chemist Joshua Jortner, Zahradník was ‘a world-leading scientist and a true aristocrat of the spirit’. Over decades he was a reliable mentor and selfless friend to countless students and colleagues; in dark times he provided support and gave hope in seemingly hopeless situations. His motto was ‘look ahead, and trust and connect people’.

Zahradník’s attitudes were forged within his symbiotic marriage with Milena Zahradníková, whom he met in an underground shelter during the Prague Uprising in May 1945. Milena died six days before Rudolf.

Helmut Schwarz
Technical University of Berlin, Germany

Bretislav Friedrich
Fritz Haber Institute of the Max Planck Society, Germany

Colourful memories

Derek Lowe’s description of the history of the discovery of ferrocene brought back some vivid memories of the early 1970s in the medicinal chemistry department of Fisons Pharmaceutical Division, Loughborough, UK (now integrated into AstraZeneca, with its research operations in Cambridge). I had joined a team that was preparing acyl ferrocene derivatives and this resulted in one of the more colourful periods in my 55-year fascination with organic chemistry.

It seems that I always had an affinity for colourful chemistry. This started at school with the reaction of phenyldiazonium chloride with any likely looking substrate from the chemical stores; I still have a sample of the orange-red product (Sudan-1) from the reaction with 2-naphthol. This was followed by the six-step synthesis of azulene from naphthalene (a two-week undergraduate project at Birmingham). The colourful chemistry in Loughborough, with its synthesis of acyl ferrocenes, was later rivalled by the electrochemical oxidation of 2-aminodiphenylamines to produce clofazimine analogues.

Given its well-known chemical relationship to aromatic compounds, ferrocene was particularly easy to acylate, and the majority of our products were, like ferrocene, orange crystalline solids. The most obvious advantage of working with ferrocene derivatives was their straightforward chromatographic separation from any unreacted ferrocene; this was characterised by a clearly-visible sequence of orange bands eluting from a silica gel column. Given the intense colour of most of our acylation reactions, it was also easy to see who was a neat and tidy chemist!

Unfortunately, senior managers outside the research departments did not share our enthusiasm for ferrocenes and I moved on to other, more successful, projects; nevertheless, I still have fond memories of some colourful chemistry in the 1970s.

Frank Ince FRSC
Loughborough, UK

Significant efforts 

Andrea Sella suggests that chemists should be taught to consider the risks, rewards and long term environmental issues associated with their work, emphasising the case of organochlorine insecticides.

I joined Shell Research’s Sittingbourne Research Centre in 1965, becoming a small part of the world-class research effort there, which investigated the efficacy, toxicology, environmental impact and metabolism of the organochlorine insecticides aldrin, dieldrin and endrin. We worked honestly and with a proud knowledge of the great benefit that those products afforded the human race on a worldwide scale. Some of the best published research in that field emanated from our laboratories. The electron capture detector made it possible to detect minute traces of those products in the environment, but the significance of those residues was much more difficult to determine. To a large extent that is what we strived to do. It is that significance that is of utmost importance in any meaningful assessment of risk.

The environmental persistence of those insecticides has become legendary in the popular press, but examination of the scientific literature reveals that they do degrade. Metabolism is extensive.

As years passed, newer products such as pyrethroid insecticides were developed. The organochlorine insecticides had had their day. Yet I look back over the decades with pride, for the work which we assisted was of the highest standard and integrity. Hopefully Sella’s students will be able to use their skills to help mankind too.

Michael Baldwin FRSC
Sittingbourne, UK


‘What makes a good children’s science book?’ (Chemistry World, December 2020, p66), incorrectly quotes Michael Holland as saying ‘by writing a book on science, you’re going to spawn a scientist’. The correct quote is: ‘by writing a book on science, you’re not going to spawn a scientist’.

In the same issue, the Colombian village of Yolombó mentioned on p15 is actually 100km from the city of Cali; it is not the village of the same name in the neighbourhood of Medellin.