Amber L. Thompson

Jun 012011
 

Presented by:  Matthew J. Langton, Jonathan D. Matichak & Dr. Amber L. Thompson
Research Leader:  Prof. Harry L. Anderson
Published:  Chemical Science (cover article)

Fully π-conjugated porphyrin oligomers exhibit remarkable properties such as ultrafast energy migration, strong two-photon absorption and wire-like charge transport. The possibility to encapsulate them by rotaxane formation may provide valuable control over their properties by offering a unique approach to engineering intermolecular interactions. An active-template Cu-mediated Glaser coupling provides an efficient route to these structures. Data from crystals of this rotaxane were collected in-house. The porphyrin dimer is slightly twisted and non-linear, contrasting with previously reported structures which possess an inversion centre (and are thus rigorously planar). The phenanthroline units of the threaded macrocycle form tightly packed π-stacks in the crystal.

Structure of the Month - June 2011

Structure of the Month – June 2011

May 012011
 

Presented by:  Matthew Tatton & Paul Winship
Research Leader:  Prof. Timothy J. Donohoe
Published:  Angewandte Chemie International Edition

This is the final isolated intermediate in the synthesis of Neodysiherbaine A;  crystals were very small, so data were collected on I19 at Diamond.  The natural product is an excitatory amino acid isolated from the Dysidea herbacea Micronesian sponge by Sakai et al.  Biological studies have shown that (–)-neodysiherbaine A is a potent convulsant and is a highly selective agonist for KA and AMPA glutamate receptors.  (–)-neodysiherbaine A was a target as part of a research programme to develop new catalytic methods for the formation of heterocycles.  Our retrosynthesis of this led to the disconnection of the central THF ring back to a hydroxyl alkene as a precursor for our recently developed Lewis acid catalysed oxidative cyclisation.

Structure of the Month - May 2010

Structure of the Month - May 2010

Apr 112011
 

The BCA Spring Meeting was held at the University of Keele in Staffordshire.  Contributions from Chem. Cryst. included:

Richard I. Cooper, Amber L. Thompson & David J. Watkin
Standard Uncertainties and Experimental Design (Poster)

Amber L. Thompson & David J. Watkin
Unpublishable” Data:  Does My R-factor Look Big in This? (Poster)

David Watkin
What’s all this MoOing about? (Presentation)

Apr 052011
 

The results have just been announced for the latest round of applications to the John Fell Oxford University Research Fund.  Our proposal for funding for a temperature controlled Peltier stage microscope with polarizing filters for the study of solid-state phase transitions in crystalline materials was successful.  Polarized light allows the ready detection of discontinuous changes in the anisotropy of a material during heating or cooling since discontinuity in any property is symptomatic of a phase change (an order-disorder transformation, a change in crystal symmetry, or the formation of a completely new phase). Studying such phase changes using a temperature controlled stage can assist in optimising conditions for obtaining a given form of a material, and also leading to an understanding the nature or mechanism of the transformation.

Apr 012011
 

Presented by: Nicholas G. White & Dr. Fabiola Zapata
Research Leader: Prof. Paul D. Beer
Published: Journal of the American Chemical Society

Both the mixed bromide/PF6 and mixed iodide/PF6 salt of this bis-iodoimidazolium macrocycle crystallize in the unusual cubic spacegroup I m -3 (there are currently only six organic structures in this spacegroup in the CSD).  The macrocycle binds anions strongly and selectively in competitive methanol/water solvent mixtures, with anions being bound solely by halogen-bonding interactions.  In the solid state, the both the bromide and iodide salts of the macrocycle exist as a dimer, with two macrocycles each pointing at two halide anions.  Experiments are being undertaken to see if this arrangement occurs in solution.

Structure of the Month - April 2011

Structure of the Month – April 2011

Mar 172011
 

Keith Prout died quite suddenly in September 2007 after a short illness.

Although he had been officially retired for several years, he was continuing an active research program with Nick Rees combining X-ray and NMR studies.  X-ray structure analysis gives information about disorder and thermal vibrations in crystals. When combined with solid state NMR a complete dynamic profile of the crystal can be obtained.

Previous studies of penicillins, ansa-titanocenes and tri-ethyl phosphate molecular complexes with various hosts suggest a variety of molecular motions in addition to the ‘translation-libration-screw’ motion derived from the crystallographic atomic displacement parameters.  He also studied  order/disorder phase transitions, molecular motion and chiral selectivity in deoxycholic acid molecular complexes.

Mar 162011
 

Dr. Violeta JevtovicVioleta is an assistant professor in the Chemistry Department at the University of Novi Sad, Serbia.  She obtained her Ph.D. in coordination chemistry studying the synthesis, structure and biological activity of transition metal compounds and visited for a few months to learn more about crystallography.