Quantitative scale for halogen bonding and hydrogen bonding: a foundation for self-assembly
Lead Research Organisation:
University of York
Department Name: Chemistry
Abstract
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Organisations
Publications
Loader J
(2014)
Highly fluorinated naphthalenes and bifurcated C-H?F-C hydrogen bonding
in CrystEngComm
Pike SJ
(2019)
Benchmarking of Halogen Bond Strength in Solution with Nickel Fluorides: Bromine versus Iodine and Perfluoroaryl versus Perfluoroalkyl Donors.
in Chemistry (Weinheim an der Bergstrasse, Germany)
Robertson C
(2014)
A solvent-resistant halogen bond
in Chem. Sci.
Robertson CC
(2017)
Hydrogen bonding vs. halogen bonding: the solvent decides.
in Chemical science
Smith DA
(2015)
The Contrasting Character of Early and Late Transition Metal Fluorides as Hydrogen Bond Acceptors.
in Journal of the American Chemical Society
Smith DA
(2014)
Metal hydrides form halogen bonds: measurement of energetics of binding.
in Journal of the American Chemical Society
Thangavadivale V
(2018)
Self-complementary nickel halides enable multifaceted comparisons of intermolecular halogen bonds: fluoride ligands vs. other halides.
in Chemical science
| Description | The scientific objectives of the award fell into three categories (A-C), which are discussed in more detail below. The objectives expected within the timeframe of the award have been met or even surpassed for objectives A and B. The new results also clearly indicate that much more of great research interest and value to a broad research community could be achieved in these areas. Objective C was always a much longer term aim and the expectation was that progress could be made in this area in the timeframe of the award and that a foundation could be laid for a future unified scale for evaluating and application of intermolecular interactions across a broad area of science. Such progress has been made, allowing a clearer picture of how to move forward with this long-term objective. A. Quantifying transition metal hydrogen-bond and halogen-bond acceptors. Substantial progress has been made in quantifying the strength of both hydrogen bonds and halogen bonds involving halide and pseudo-halide ligands bound to transition metals. These are important in expanding the knowledge and utility of these important intermolecular interactions in inorganic chemistry, where applications include supramolecular assembly, catalysis, and molecular sensing. During the period of the award two full papers have been published in the top chemistry journal Journal of the American Chemical Society, and are likely to be of high impact. One paper reports for the first time that hydride ligands can function as halogen bond acceptors. The corresponding report, some 20 years ago, that hydride ligands can function as hydrogen bond acceptors, launched worldwide activity in organometallic chemistry related to this discovery. The second paper quantifies and explains the dramatic difference in hydrogen bond acceptor capability of fluoride ligands bound to early and late d-block metals, and demonstrates that such second-sphere coordination interactions can serve as reporters of the metal centre itself. A third paper has been submitted that describes the effect of halogen bonding in the crystalline state via X-ray crystallography and NMR spectroscopy. Here we have designed self-complentary cmolecules that interact with one another to form halogen-bonded chains.Further publications will report quantification of hydrogen bonds or halogen bonds involving a variety of other ligands. B. Quantifying halogen bonds involving organic acceptor groups. Very significant progress has been made in meeting this objective. One of the questions regarding such halogen bonds has been whether they can be explained solely in electrostatic terms or whether (and to what extent) charge-transfer considerations are important in understanding the strength of the interactions. In a very significant paper published in the Royal Society of Chemistry's flagship journal Chemical Science, we were able to demonstrate the importance of charge-transfer contributions to strong halogen bonds and show how this leads to a very different response to solvent to that of hydrogen bonds. We have been able to build upon this finding to develop means of using solvent to control intermolecular interactions and have reported these ffects in a second publication in Chemical Science. We have also been able to make progress in quantifying halogen bonds involving charged organic species and will report these results in the near future. C. Quantitative scales for hydrogen-bond and halogen-bond donor and acceptor strengths. We have reported, for the first time, a comparison between hydrogen bond acceptor strengths of metal-bound ligands with organic hydrogen bond acceptors, using a single scale, the scale developed by Hunter and previously applied to organic functional groups. The results, published in Journal of the American Chemical Society, show that fluoride ligands bound to late transition metals (Ni, Pd, Pt) are as strong a hydrogen bonds acceptor as the strongest known acceptors among organic functional groups (e.g. phosphine oxides and N-oxides) and that fluoride ligands bound to early transition metals (Ti, Zr, Hf) are hydrogen bond acceptors of comparable strength to organic groups such as aniline and pyridine. We have also made significant progress in developing empirical computation models for halogen bonding that we expect in future to provide predictive capability for halogen bonding. This work requires further development and will be reported at a later stage, but the award has enabled very significant progress to be made. The research accomplishments have also led to a number of opportunities and invitations for members of the research team to present this work at national and international conferences, details of which are provided in other parts of the report. The most immediate impact and opportunity to take the work forward will be come from academic scientists with interests in intermolecular interactions and self-assembly. Such scientists, however, represent a very broad community across the chemical sciences and in neighbouring disciplines of materials science, molecular biology and pharmaceutical sciences. The published work form this award, which will be augmented by further publications from the principal investigators beyond the lifetime of the award, is fundamental in nature, but provides a quantitative framework for understanding and application of intermolecular interactions, which will be applicable in the design of new materials, catalysts and pharmaceuticals, among many examples. |
| Exploitation Route | They will be used by other acedmics to design new compounds exhibiting halogen bonds and hydrogen bonds |
| Sectors | Chemicals Energy Pharmaceuticals and Medical Biotechnology |
| Description | The research is fundamental in nature and its aim has been to develop and improve our understanding of key intermolecular interactions, specifically hydrogen bonds and halogen bonds, across all of chemistry and, in particular, to develop and enhance predictive capabilities for applications involving use of such interactions. This has been done by providing a quantitative foundation for evaluating and applying such intermolecular interactions that can in future will be able to be deployed on many current research problems across the science and technology area. The physical properties as well as most of the functional properties of molecular systems in chemistry, biology and materials science are all governed by non-covalent interactions. Thus, the research form this award underpins many areas of science that are related to self-assembly or directed assembly of molecules or molecular building blocks. The insights arising from this award are applicable in fields like organocatalysis, biocatalysis, transition metal catalysis, process chemistry, drug design, sensor design, molecular machines, smart polymers and nanotechnology to name a few areas where there is much current activity. The economic and societal impact will derive from research progress in these areas and will be felt in the long term rather than the short term (i.e. period of the award). The project has also produced three young scientists with training and expertise that spans the traditional disciplines of organic, inorganic, physical and theoretical chemistry, with experience of working in a collaborative team. Two were based in York (award EP/J012955/1) and one in Sheffield (award EP/J012998/1). Their skills and experience will make them attractive potential employees across many areas of the chemical industries: pharmaceutical, agrochemicals, dyes, liquid crystals and polymers, including basic R&D, chemical engineering, manufacturing and process chemistry. Indeed one of the three has moved on to work for a company in the area of catalysis and the other two have remained employed in academia. |
| First Year Of Impact | 2016 |
| Sector | Chemicals |
| Impact Types | Societal Economic |