New research allows chemists to ‘see’ a chemical bond formed

Novel research involving Southampton’s National Crystallography Service (NCS) is using newly developed solid-state NMR techniques to enable chemists to ‘see’ how a chemical bond is formed. 

This high-resolution quantum crystallography technique has never before been used to systematically look at a bond being formed, and is a collaboration between the universities of Southampton, Nottingham Trent and Warwick. The impact of their work has recently been recognised with a paper being published in the prestigious chemistry journal Angewandt Chemie as a ‘Hot Paper’ (one of its top 10 per cent most important papers). 

Professor Simon Coles, Director of NCS, led Southampton’s contribution to the work. He says: “This research is about being able to ‘see’ how a chemical bond forms, which you can’t do with many experimental techniques. The only way to do this at a resolution that allows you to ‘see’ the electrons involved, is in a crystal. This high-resolution single crystal X-ray diffraction allows us to look at maps of where the electrons are, rather than the more traditional ‘balls and sticks’ that we are used to seeing in molecular structures.” 

Professor John Wallis, from Nottingham Trent University, masterminded the synthesis of novel molecules suitable for this study. By adding different functional groups to one of two interacting (but not bonded) atomic centres, the level of interaction between the two atoms could be tuned to see one atom increasingly ‘reaching out’ to the other to form a bond. 

The University of Warwick group, led by Professor John Hanna, performed solid-state NMR experiments, a technique that can detect non-bonded interactions between atoms, and developed a cutting-edge new approach based on double isotopic labelling that can be applied to many different areas. 

Simon says the results of the research provide a fundamental understanding of how much difference a chemical change actually makes when ‘adding electrons’ and gives insight into a whole range of different types of chemistry involving intermolecular interactions. 

He adds: “For a chemist to be able to ‘see’ a chemical bond being formed is truly exciting and provides a fundamental understanding of our subject. Being able to ‘tune’ a system to control whether a bond forms or not gives much more control over chemical synthesis and even more over chemical reactivity.” 

The NCS was involved in the high-resolution X-ray diffraction part of the research and Simon says the work is a testament to the skills and capabilities of the NCS and its staff. 

“We are looking to include these advanced techniques as part of our service offering from next year, so this gives us some kudos and is a great example to the wider chemistry community of what we can do,” he says. 

The research builds on work by the three universities that started more than a decade ago and involved the University of Southampton’s current President and Vice-Chancellor Professor Mark E Smith. Mark at that time led the University of Warwick’s Solid State NMR group and was a Principal Investigator on the original EPSRC-funded project.