Prof. Jonathan W. Steed

Personal web pages

(email at jon.steed@durham.ac.uk)

Biography

Jonathan W. Steed was born in Wimbledon, UK in 1969. He obtained his B.Sc. and Ph.D. degrees at University College London, working with Derek Tocher on coordination and organometallic chemistry directed towards inorganic drugs and new metal-mediated synthesis methodologies. He graduated in 1993 winning the Ramsay Medal for his Ph.D. work. Between 1993 and 1995 he was a NATO postdoctoral fellow at the University of Alabama and University of Missouri, working with Jerry Atwood, where he developed a new class of organometallic supramolecular hosts for anions. In 1995 he was appointed as a Lecturer at Kings College London where he built up a reputation for supramolecular chemistry including anion binding and sensing, and crystal engineering studies using strong and weak hydrogen bonds. In 1998 he was awarded the Royal Society of Chemistry Meldola Medal and he was promoted to Reader in 1999. In 2004 he moved to Durham University where he is currently Professor of Inorganic Chemistry. Prof. Steed is co-author of the textbooks Supramolecular Chemistry (2000) and Core Concepts in Supramolecular Chemistry (2007) and more than 200 research papers. He has published a large number of reviews, book chapters and popular articles as well as two major edited works, the Encyclopaedia of Supramolecular Chemistry (2004) and Organic Nanostructures (2008). He has been an Associate Editor of New Journal of Chemistry since 2001 and is the recipient of the Vice Chancellor's Award for Excellence in Postgraduate Teaching (2006). See personal web pages for full details.

Supramolecular Chemistry

Traditional molecular chemistry is largely concerned with the synthesis and study of molecules linked by covalent bonds between atoms. However, there is another entire area of chemistry, often impinging on nanometre scale assemblies, that transcends the chemistry of the covalent bond. This is termed supramolecular chemistry and it involves the study of systems bonded by a multitude of non-covalent interactions, particularly hydrogen bonding, π-π stacking, and metal-ligand dative bonds. Many of these kinds of interactions are difficult to control yet their importance and potential is mind blowing. For example, in biochemistry Nature relies heavily on just these interactions to fold proteins into their active conformations and, crucially, it is hydrogen bonding (base pairing) and π-π stacking that give DNA its characteristic double helical shape.¹

Molecular Sensors

Our work encompasses many aspects of supramolecular chemistry from the nature of individual interactions (particularly in the solid state) to their incorporation and use in functioning molecular devices, particularly in applications such as the design and synthesis of molecular sensors for anions (e.g. environmental pollutants). To take just one example, a complex molecular device based on a calixarene (shown on the right) is capable of selectively recognising and binding a two halide anions entirely through non-covalent interactions (NH···X and CH···X hydrogen bonds) and photochemically signalling that binding via the appended pyrene units.^2-5

Supramolecular Gels

Gels comprise a liquid trapped by a highly porous network of nanometre-scale fibres. As well as being fascinating because of their nanoscale structure, recent work has shown that the highly porous, partially ordered network in gels, coupled with their formation by spontaneous self-organization gives them tremendous technological possibilities, for example as selective sorbents or uptake agents, in the controlled formation of highly porous polymers and in the synthesis and support of catalytic nanoparticles. We have discovered an extremely simple, readily prepared series of rigid bis(urea) building blocks in which gelation occurs to give gels via a hierarchical series of self-organization steps strongly influenced (both positively and negatively) by metal salts. The intrinsic ability of bis(ureas) to aggregate via NH∙∙∙O=C hydrogen bonded interactions is modulated and can be switched on and of by reversible coordination interactions to metal cations and hydrogen bonding to conjugate anions. The resulting gels and the consequent nanostructuring of a wide variety of metal salts offers interesting technological possibilities. An SEM image of a dried gel showing chiral helical fibres derived from a chiral gelator is shown right.^{6, 7}

Crystallography

Facilities at Durham for both single crystal and powder work are internationally leading. The group is also particularly active in structure determination by neutron diffraction and students have the opportunity of taking part in visits to facilities at the ILL in Grenoble, France or the ISIS facility in the UK. Our single crystal neutron structure of the exotic H₇O₃⁺ ion trapped by two molecules called ‘crown ethers’ is shown right. We are particularly interested in low symmetry crystal structures with more than one molecule in the asymmetric unit⁸ and we maintain a dedicated web resource on this work (http://www.dur.ac.uk/zprime).

References

1. J. W. Steed and J. L. Atwood, 'Supramolecular Chemistry', J. Wiley & Sons: Chichester, 2000.
2. K. J. Wallace, W. J. Belcher, D. R. Turner, K. F. Syed, and J. W. Steed, "Slow anion exchange, conformational equilibria, and fluorescent sensing in Venus flytrap aminopyridinium-based anion hosts", J. Am. Chem. Soc., 2003, 125, 9699.
3. J. Zhang, A. M. Bond, J. Belcher, K. J. Wallace, and J. W. Steed, "Electrochemical studies on the modular podand 1,3,5-tris(3- ((ferrocenylmethyl)amino)pyridiniumyl)-2,4,6-triethylbenzene hexafluorophosphate in conventional solvents and ionic liquids", J. Phys. Chem. B, 2003, 107, 5777.
4. M. H. Filby, T. D. Humphries, D. R. Turner, R. Kataky, J. Kruusma, and J. W. Steed, "Modular Assembly of a Preorganised, Ditopic Receptor for Dicarboxylates", Chem. Commun., 2006, 156.
5. D. R. Turner, E. C. Spencer, J. A. K. Howard, D. A. Tocher, and J. W. Steed, "A modular, self-assembled, separated ion pair binding system", Chem. Commun, 2004, 1352.
6. L. Applegarth, N. Clark, A. C. Richardson, A. D. M. Parker, I. Radosavljevic-Evans, A. E. Goeta, J. A. K. Howard, and J. W. Steed, "Modular nanometer-scale structuring of gel fibres by sequential self-organization", Chem. Commun, 2005, 5423.
7. C. E. Stanley, N. Clarke, K. M. Anderson, J. P. Lenthall, and J. W. Steed, "Anion Binding Inhibition of the Formation of a Helical Hydrogel", Chem. Commun., 2006, 3199-3201.
8. J. W. Steed, "Should solid-state molecular packing have to obey the rules of crystallographic symmetry?" CrystEngComm, 2003, 5, 169.