Science | Dave Allan

Dave Allan
Single Crystal Diffraction

Dave Allan Dave Allan is the Principal Beamline Scientist on the small-molecule single-crystal diffraction beamline, I19. Before his appointment at Diamond, Dave was a lecturer in The School of Physics at The University of Edinburgh and he laterally held an EPSRC Advanced Research Fellowship within The School of Chemistry, where he retains visitor status. His main research interests involve the high-pressure and low-temperature polymorphism of small-molecule systems and the development of in situ crystal growth techniques.

Dave is also vice-President of the British Crystallographic Association.

Email: Dave Allan
Tel: +44 (0) 1235 778644
Beamline I19: Single Crystal Diffraction

Key Research Interests

Small-molecule single-crystal diffraction; in situ crystal growth techniques; high-pressure structural studies; polymorphism; phase transitions; technique development .

Current Research Interests

Molecular materials contain a rich spectrum of interaction types - from the relatively weak van der Waals interaction, through the more moderate ionic bond and hydrogen bond, to the relatively strong covalent bond. As these interactions are acutely sensitive to intermolecular distance and thermal vibration, high-pressure and variable temperature offer a powerful means of altering their relative hierarchy of strengths.

A systematic study of molecular systems under varying thermodynamic conditions is rewarding, therefore, as competition between the various interaction types causes phase transitions, including glass formation, and effects melting, crystal solubility and nucleation. Despite the rich structural behaviour we expect to be exhibited by molecular systems at non ambient conditions, until comparatively recently the majority of research, particularly in high-pressure structural science, has focused on the study of fundamental systems such as the elements and simple compounds, for example alloys, semiconductors and minerals. With the exception of molecules of relevance to planetary science (such as ice, methane and ammonia) there has been comparatively little work conducted on simple, generic, molecular systems containing common functional groups such as the monoalcohols, monocarboxylic acids, ketones and simple derivatives of, for example CN, NO2 and NH2. The work on these simple systems has proved to be timely as there is a growing interest from the academic (Physics, Chemistry and Biology) and the industrial (Pharmaceutical and Petrochemical) communities for a deeper understanding of how the molecular interactions affect the behaviour of molecular systems and how their properties and crystal structures can be predicted.

The aim of my research is to establish how a variety of molecular systems respond to pressure and temperature and the scope of materials selected has ranged from simple organic systems, such as simple monofunctional systems and amino acids through to polypeptides and pharmaceutical compounds, and has also involved the pressure tuning of inorganic and organometallic compounds. Over the course of the research, new techniques have been developed for in situ crystal growth from the melt or from solution, which has markedly increased the range of systems studied, and the quality of high-pressure single-crystal x-ray diffraction structural studies was improved dramatically with the introduction of beryllium-free diamond-anvil cells and more optimised data collection procedures.

Selected Publications

  1. Blake A.J., Champness N.R., Easun T.L., Allan D.R., Nowell H., George M.W., Jia J. and Sun X-Z Photoreactivity examined through incorporation in metal-organic frameworks, Nature Chemistry (2010) doi:10.1038/nchem.681
  2. Allan D.R., Marshall W.G., D.J. Francis D.J., Oswald I.D.H., Pulham C. R. and Spanswick C., The crystal structures of the low-temperature and high-pressure polymorphs of nitric acid, Dalton Transactions, 39 (2010) 3736-3743
  3. Grazia Bezzu C., Helliwell M., Warren J.E., Allan D.R., McKeown N.B., Heme-like coordination chemistry within nanoporous molecular crystals., Science 327 (2010), 1627-1630
  4. Yan Y., Telepeni I., Yang S., Lin X., Kockelmann W., Dailly A., Blake A.J., Lewis W., Walker G., Allan D.R., Barnett S., Champness N., Schroder M., Metal-Organic Polyhedral Frameworks: High H2 Adsorption Capacities and Neutron Powder Diffraction Studies, Journal of the American Chemical Society, 132 (2010), 4092-4094
  5. McConnell A.J., Serpell C.J., Thompson A.L., Allan D.R. and Beer P.D., Calix[4]arene-Based Rotaxane Host Systems for Anion Recognition, Chemistry - A European Journal 16 (2009), 1256-1264
  6. Fabbiani F.P.A., Allan D.R., Francis D.J., Marshall W.G. and Pulham C.R., A high-pressure form of sulfuric acid monohydrate as determined by x-ray and neutron diffraction, Inorganica Chimica Acta 361 (2008) 487-494
  7. Minguez Espallargas G., Brammer L., Allan D.R., Pulham C.R., Robertson N. and Warren J.E., Noncovalent interactions under extreme conditions: high-pressure and low-temperature diffraction studies of the isostructural metal-organic networks (4-Chloropyridinium)2[CoX4] (X = Cl, Br), J. Am. Chem. Soc. 130 (2008) 9058-9071
  8. Moggach S.A., Allan D.R. Parsons S., Warren J.E. Incorporation of a new design of backing seat and anvil in a Merrill-Bassett diamond anvil cell, J. Appl. Cryst. 41 (2008), 249-251
  9. Walker M., Morison C.A., Allan D.R., Pulham C.R. and Marshall W.G., A new high-pressure phase of sodium formate dihydrate; an experimental and computational study, Dalton Transactions 2014-2019 (2007)
  10. Fabbiani F.P.A, Allan D.R., David W.I.F., Davidson A.J., Lennie A.R., Parsons S., Pulham C.R. and Warren J.E., High-pressure studies of pharmaceuticals: an exploration of the behaviour of piracetam, Crystal Growth & Design, 7 (2007)