Iron-containing triple helicate hosts that are a potential first step towards anion sensors have been designed by chemists in Ireland.

Paul Kruger and Sandrine Goetz from Trinity College Dublin say their complexes, which contain ligands based on amide and bipyridyl functional groups, are the first of their kind to have receptors inside the helices that can form hydrogen bonds with anions. 

The presence of a guest anion within the helical cavity causes changes in the ligands that can be analysed easily to determine what is inside. 

The researchers say that the shape of the anion might affect how it bonds to the host complex. Out of several anions tested, the spherical chloride anion was the only one with the right shape to bind in the helix cavity.

Kruger's group are now planning to make similar host complexes containing other metals which they hope may act as potential luminescent or redox anion sensors. 

Niamh O'Connor