Prof Derek Tocher

Research Overview

Chemical crystallography is a tool that is used by chemists irrespective of their affiliation with organic, inorganic or organometallic chemistry. It is also an invaluable tool for many computational chemists. As a consequence we are involved in many collaborative projects with other chemists providing key data structural data.

Polymorphism

For the last few year much of our effort has focused on a major theoretical/experimental project on the 'Prediction of Organic Crystal Structures' (with Prof. S.L. Price and others) funded by Research Councils UK Basic Technology Programme. The phenomenon of polymorphism is the ability of a material to take more than one crystalline form and is an important problem facing many industries. For example the detonation properties of an explosive are a function of the material's crystal structure. Transformation from one polymorph to another may result in increased sensitivity and threat of unplanned explosion! Perhaps the most serious area where this is a problem is in the pharmaceutical industry where different polymorphs will have different solubilities and therefore have a dramatic effect of the safe or effective dose of a drug that can be administered to a patient. The project involves the careful study of crystallisation conditions for target molecules such that new polymorphs may be discovered, and to compare those we find experimentally with those predicted from theoretical studies. Laboratory crystallization studies at UCL are complemented by work on a medium throughput automated screening robot carried out in the group of Dr Alistair Florence at the University of Strathclyde. Laboratory based X-ray crystallography is complemented by neutron work at the ISIS facility.

Calculated ribbon motif for 5-fluorocytosineObserved ribbon motif for 5-fluorocytosine

Calculated and observed ribbon motifs for 5-fluorocytosine

Organic Chemistry

Other studies encompass providing key stereo-chemical information on important organic species (with Professors Caddick and Motherwell) in chemical biology and transition metal catalysed reactions among others.

Inorganic/Organometallic Chemistry

We are also heavily committed to supporting organometallic/inorganic/materials chemistry by providing structural data to several research groups (Prof. Carmalt and Dr Sella) working in areas such as precursor design for chemical vapour deposition, supramolecular chemistry, and lanthanide chemistry, as well as having several productive international collaborations in this area.

Publications

  1. A New thermodynamically stable polymorph of 5-fluorouracil found following computational crystal structure predictions.A.T Hulme, S.L Price and D.A. Tocher, J. Am. Chem. Soc., (2005), 127, 1116-1117.
  2. The discovery of new crystal forms of 5-fluorocytosine consistent with the results of computational crystal structure prediction.A.T. Hulme and D.A. Tocher, Cryst. Grth. & Design., (2006), 6, 481-487.
  3. The solvates of o-acetamidobenzamideS.A. Barnett, D.A. Tocher and M. Vickers, CrystEngComm., (2006), 8, 313-319.
  4. Racemic Progesterone: predicted in silico and produced in the solid state.R.W. Lancaster, P.G. Karamertzanis, A.T. Hulme, D.A. Tocher, D.F. Covey, and S.L. Price, Chem. Commun., (2006), 4921-4923.
  5. A systematic experimental and theoretical study of the crystalline state of six chloronitrobenzenes.S.A. Barnett, A. Johnston, A.J. Florence, S.L. Price and D.A. Tocher, Cryst. Grth. & Design., (2008), 8, 24-36.
  6. The observed and energetically feasible crystal structures of 5- substituted uracilsS.A. Barnett, A.T. Hulme, N. Issa, T.C. Lewis, L.S. Price, D.A. Tocher, and S.L. Price, New J. Chem., (2008), 32, 1761-1775.
  7. Salt or Co-crystal? A new series of crystal structures formed from simple pyridines and carboxylic acids.S. Mohamed, D.A. Tocher, M. Vickers, P.G. Karamertzanis and S.L. Price, Cryst. Grth. & Design., (2009), 9, 2881-2889.
  8. A computationally inspired investigation of the solid forms of (R)-1-phenylethylammonium-(S)-2-phenylbutyrate.K.D. Antoniadis, E. D'Oria, P.G. Karamertzanis, D.A. Tocher, A.J. Florence, A.G. Jones, S.L. Price, Chirality, (2010), 22, 447-455.