Chemical Crystallography

Presented by:  Nicola K. S. Davis & Dr. Amber L. Thompson
Research Leader:  Prof. Harry L. Anderson
Published:  Journal of the American Chemical Society

Molecules with large planar π-systems show a strong tendancy to aggregate due to π-π interactions. This tetra-anthracene-fused porphyrin forms dimers with the molecules twisted with respect to each other. Bulky aryl groups were necessary for characterisation, but prevent the porphyrins from forming longer stacks in the crystal.  Using long alkyl chains instead could yield systems which form longer π-stacked arrays which may form discotic liquid crystals.  Furthermore, as the porphyrins stack with a near-zero horizontal offset, these have potential as light harvesting arrays since the alignment of the chromophores provides an efficient pathway for holes and electrons along the column.

Structure of the Month – November 2010

Presented by:  Dmitry Kondratiuk, Johannes Sprafke & Dr. Amber L. Thompson.
Research Leader:  Prof. Harry L. Anderson
Published: Journal of the American Chemical Society

Molecules with many strongly coupled π-electrons exhibit unique optical and electronic behaviour because of the way they interact with electric fields, particularly high-frequency optical fields.  The crystals of this material are highly prone to solvent loss as well as giving weak diffraction.  Data were collected on I19 at Diamond and the structure featured on at least four proposals at Diamond and the SRS (Daresbury) before it was finally determined.  Butadiyne linked porphyrin oligomers are generally expected to be rigid, but this structure shows that they are actually quite flexible and can be severely bent to form this highly strained ring.

Structure of the Month – August 2010