Missed the first YC session in BCA Spring Meeting?
Here are the abstracts of their presentations:
1. Structural analysis of metal coordination complexes under pressure.
– Henry Wong (University of Nottingham)
2. 250 Structures later – Friendly Relationships in a Compound Family
– Susanne Coles (University of Southampton)
3. High-throughput metallo-protein analysis by microPIXE
– Oliver Zeldin (University of Oxford)
4. Thermal and photocrystallographic studies on a nickel-nitro complex
– Lauren Hatcher (University of Bath)
5. Structure solution of two nicotinamide : succinic acid cocrystals
– Laura Thompson (University of Birmingham)
6. Flexibility in cadmium and mercury imidazolate frameworks
– Ines Collings (University of Oxford)
Structural analysis of metal coordination complexes under pressure
H. Wong, A.J. Blake, J. McMaster, and M. Schröder, School of Chemistry, University of Nottingham; D.R. Allan, Diamond Light Source, Harwell Science and Innovation Campus.
A series of palladium thioether coordination complexes have been studied using high pressure crystallography. This study expands upon previous work [1] by examining the effect of pi-acceptor ligands on these systems.
In one of these complexes, a coordinated triphenylphosphine ligand shows a pronounced structural deformation due to pressure. The process involves pi-pi stacking with a neighbouring cation; the evolution of the geometry of this pi-pi stacking can be followed as a function of pressure. We are developing arguments to explain the geometric and electronic changes within this structure by using molecular orbital theory and other computational techniques. [2] [3]
250 Structures later – Friendly Relationships in a Compound Family
L. S. Coles (née Huth), T. L. Threlfall and M. B. Hursthouse, School of Chemistry, University of Southampton, Southampton, UK.
The assembly of functionalised organic molecules in the solid state has attracted much recent interest, due to its relevance to both the production of pharmaceuticals and other industrially important compounds on one hand, and the search for novel materials with utilisable properties on the other. Hence small molecule X-ray crystallography has become an important technique for the detailed investigation of the solid state ultimately aiming to understand the (supra) molecular assemblies in crystal structures. With the advent of high-throughput-crystallography large amounts of data are now routinely generated providing the opportunity to analyse this data in a meaningful way. The systematic study of crystal packing patterns together with the application of theoretical calculations can improve the insight into the solid state assembly, providing feedback for design and prediction procedures.
Here we present the results from our recent case study, which is concerned with the crystallisation and packing preferences of a large set of mono-substituted acylanilides – including the important pharmaceutical paracetamol. An extensive array of closely related molecules has been synthesised: In the course of one year, over 400 closely related acylanilides have been prepared yielding approximately 300 crystalline samples, and more than 250 data sets have been collected, corresponding to ca. 200 actual novel crystal structure determinations of acylanilides. Crystal structures of this extensive family of mono-substituted acylanilides have been systematically cross-examined and structural relationships have been identified with the program XPac [1]. Furthermore, tendencies and trends in the crystallisation process have been observed dependent on the molecular changes. The results of this systematic study will be presented and discussed.
High-throughput metallo-protein analysis by microPIXE
OB Zeldin and EF Garman, Department of Biochemistry, University of Oxford; GW Grime, Ion Beam Centre, University of Surrey, Guilford.
Unambiguous identification of metals in structures and finding their binding stoichiometry can be difficult tasks for macromolecular crystallographers. MicroPIXE is a powerful technique that uses a high energy proton beam to excite secondary X-ray emissions from the atoms present in a sample. This provides unique identification of the bound elements. By normalising to the sulphur signal from the cysteines and methionines, and knowing their number from the primary sequence, we can additionally infer the stoichiometry of the bound elements [1]. It would be highly desirable to be able to compare binding affinity and metal presence under a variety of conditions: both across various buffers and through mutant series. These goals are currently limited by the cost and throughput of the technique, limiting it to <10 samples per day. We are developing high throughput sample preparation and data analysis techniques with the goal of increasing the capacity to well over 100 samples per day and thus fundamentally changing the way that this technique is applied. We will present our results on array preparation and analysis techniques and discuss the consequences that a high throughput approach will have on the way that microPIXE is used by macromolecular crystallographers.
Thermal and photocrystallographic studies on a nickel-nitro complex
L. Hatcher, Department of Chemistry, University of Bath.
The technique of time-resolved crystallography has attracted much interest in recent years, as a result of rapid technological advancements in the field. These methods introduce the “fourth dimension” of time into the crystallographic experiment, allowing the structures of short-lived and metastable species to be determined [1].
In this work, nitro-(n1-NO2) to nitrito-(n1-ONO) linkage isomerisation in the complex [Ni(Et4dien)(NO2)2] (Et4dien = N,N,N’,N’-tetraethyldiethylenetriamine) has been studied using time-resolved crystallographic techniques. Significant levels of conversion are induced in the single-crystal when the complex is excited both photochemically and thermally. 86% conversion to the metastable nitrito-(n1-ONO) linkage isomer is achieved following irradiation with UV light, and a maximum 42% conversion is thermally induced when variable temperature studies are conducted between 100 K and 370 K. This is the first crystallographic study to report both thermal and photochemical excitation of the nitro ligand in the same system.
Structure solution of two nicotinamide : succinic acid cocrystals
L. Thompson, M. Tremayne, School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT.
Molecular cocrystals are becoming increasingly important within the pharmaceutical industry as they represent a new source of solid-state materials which have the potential to provide optimal physical properties of the individual component [1]. Traditionally cocrystals are synthesised by recrystallisation of components through solvent evaporation, however alternatives such as solvent drop grinding can be used providing many advantages including green credentials and access to other stoichiometric combinations [2].
Single crystal X-ray diffraction is the most widely used method of structure solution, however solid-based synthesis and poor crystallisation behaviour means that some molecular crystals do not form crystals of sufficient quality for single crystal experiments, hence the ability to solve crystal structures from powder X-ray diffraction (PXRD) is vital. The use of PXRD data to solve crystal structures is a constantly developing area of research [3] which remains both academically and industrially significant.
In this talk, I will discuss the differences in the crystal structures of two stoichiometrically different nicotinamide : succinic acid cocrystals, one of which was solved by single crystal [4] and the other from PXRD due to its inability to form single crystals. The benefits of using powder X-ray diffraction data collected from a synchrotron light source in this structural investigation will also be presented.
Flexibility in cadmium and mercury imidazolate frameworks
I.E. Collings, A.L. Thompson, and A.L. Goodwin, Department of Chemistry, University of Oxford, Oxford; M. Dove, Department of Earth Sciences, University of Cambridge, Cambridge.
Throughout the last decade, the study of metal-organic frameworks (MOFs) has remained one of the most topical fields in solid-state chemistry due to the extensive and unique range of structural and functional properties they exhibit [1].
This talk will be focused on some MOFs whose structures resemble those of silicate frameworks — namely, cadmium and mercury imidazolates [2]. We have been particularly interested in understanding the extent to which framework flexibility determines mechanical behaviour. Experimental data from variable temperature experiments using single crystal X-ray diffraction, and computer modelling
will be presented.