Chemists in the UK have developed coordination polymers that appear to adapt their symmetry to respond to the hydrogen bonding within those polymers.

Coordination polymers are compounds made of metals and ligands that extend 'infinitely' in one, two or three dimensions.  They can have very diverse properties and have potential applications in areas such as catalysis, information storage and optical switches.

The polymers made by Jonathan Steed and colleagues at the University of Durham consist of ligands that contain a thioether functional group attached to positively charged silver, associated with either a nitrate or borate anion.

Steed's team reports that, in the solid state, the nitrate anion twists in order to try to fit the hydrogen bonding pocket in the complex. In contrast, borate anions fit the pocket very well. 

According to Steed, this better fit appears to lead to the presence of two crystallographically independent molecules in the unit cell of the borate complex. Structures like this provide a rich source of information on crystal packing, he said. They are also the type of material whose crystal structure is most difficult to predict. 

Steed said these compounds 'pave the way to further work in novel directions.' The group is now undertaking a full systematic study of the system. 

Niamh O'Connor