Research |
| A wide range of research is undertaken within the group, the key areas of
which are highlighted below: |
Crystallisation |
Single crystals. |
Micro scale methods of solution crystallisation,
developed and optimised in our laboratory, are effectively used for growing single crystals of various pharmaceutical
substances. Using these methods, single crystals can be obtained from a sample of crystalline material as small as
5-10 mg. Different polymorphic modifications of a compound, including unstable ones, can be crystallised from a 1-3 g
sample. This is important for the drug development at early stages when only a small amount of pure material is
available for study. We also deal with competitive crystallisation and challenging crystal habits. |
Electron Distribution Studies |
Laplacian of rho in benzene. |
Collecting accurate, high resolution X-ray
charge density data (2θ ≥ 100°) provides information on the electron distribution within the
system under study. These studies are more challenging than 'ordinary' single crystal experiments due to the
requirements for very good quality single crystals which diffract well up to a high resolution and the need to
collect highly redundant accurately processed data. However, such investigations allow us to determine both
the nature of the bonding and the atomic interactions for a particular compound, which can provide vital
insights into its structure and behaviour. Our research in this area includes looking at the effect of
intermolecular interactions on compounds undergoing solid-state reactions (e.g. coumarin-3-carboxylic acid)
and more challenging studies determining the nature of the bonding around transition metal centres
(e.g. [Rh(C7H8)(PPh3)Cl]).
|
High Pressure |
Pressure induced chromism. |
Our current high pressure structural research
encompasses two very different areas. The first is the crystallisation of molecular liquids through the application
of pressure, often leading to markedly different phases to the solid-state formed though low temperature crystallisations.
The second area of research concerns the structural response of crystals to the application of pressure, particularly
compounds that have been shown to novel electronic or magnetic behaviours under non-ambient conditions.
The group currently has access to a number manually driven diamond anvil cells (DAC's) with attachments for use on a number
of different diffractometers.
|
In-situ Crystallisation of Liquids |
In-situ crystallisation. |
This technique provides the opportunity
to study crystal structures of compounds which are liquids or even gases under ambient conditions. Our
research interest in this area is focused on growing low-melting point co-crystals for example, a molecular
complex of methanol and chloroform. These studies are important for understanding the basic principles of
intermolecular interactions and polymorphism and also valuable for theoretical chemistry as the number of atoms
in such systems is relatively small. This area of crystal chemistry is virtually unexplored and almost every
co-crystallization experiment produces new and often unexpected results.
The laboratory is equipped with special attachments and a dedicated computer-controlled laser-based heating
device for in-situ crystal growth. |
Low Temperature Instrumentation |
Xiphos 2 K Diffractometer. |
XIPHOS has been developed to expand home
laboratory diffractometers closer to those found at central facilities, offering extremes of sample environment
and flux densities comparable to those of 2nd generation synchrotrons. The system has a minimum operating
temperature of 1.9 K, and has a direct drive rotating anode generator coupled with the latest multilayer optics.
XIPHOS has been specifically designed to accommodate various sample environments and is now operational.
Furthermore, it has been calibrated with structural phase transitions from 14-148 K. |
Magnetic Materials |
Magnetic Susceptibility of a Phosphine SCO Complex. |
One of our interests is the study of materials presenting
magnetic properties with academic and potential industrial interest, e.g. molecular magnets, spin crossover
compounds, organic ferromagnets, organic superconductors, etc. The structural characterization of these materials
is vitally important for the understanding of their behaviour and for the design of new materials showing enhanced
properties. Variable temperature X-ray single crystal diffraction studies, neutron diffraction experiments, moun
spin resonance, etc are among the techniques we use to carry out this work. |
Software Development |
 |
Olex2 is an easy-to-use
program for small-molecule structure solution and refinement. It also includes many useful
tools for structure analysis, archiving and report generation. All aspects of the structure
determination and publication process are presented in a single, workflow-driven package -
with the ultimate goal of producing an application which will be useful to both chemists and
crystallographers.
|
Solid State Photochemistry |
In-situ irradiation of a crystal with a red laser |
Solid-state chemistry is a wide ranging subject which encompasses various
light induced phenomena, there are many potential applications including molecular switches, sensors and optical storage.
Our interest in solid-state photochemistry covers a broad range of phenomena including solid state [2+2] cycloaddition
reactions, spin-crossover complexes and photochromism. Many of these studies are carried out by irradiating the samples
in-situ with either lasers or UV light.
|
