Novel chemistry with environmental applications The design of receptor systems capable of the simultaneous coordination of both cationic and anionic guest species has recently attracted a great deal of interest due to their application in crystal engineering and materials science. European researchers extended these applications by implementing halogen bonding for the development of aqueous sensors. Climate Change and Environment © Thinkstock Halogen anions, especially bromine and iodine, are situated in the periphery of organic compounds, exerting their capacity to act as electron acceptors. These non-covalent halogen bonds are being exploited in various self-assembly applications in materials science. At the same time, mechanically bonded molecules with both cationic and anionic species have the potential to act as receptors in salt solubilisation, extraction and membrane transport agents, and sensors. The EU-funded IEFACP aimed to combine such heteroditopic receptors with the properties of halogen bonding. More specifically, IEFACP scientists explored halogen bonding to develop a novel receptor capable of anion recognition properties.A series of new compounds were generated and, following structure determinations in both solution phase and X-ray solid state, these demonstrated halide anion binding via halogen bonding. In particular, a novel halogen-bonding receptor with two bromine halogen bond donor atoms was found to selectively bind bromide strongly in competitive aqueous solvent media. This new anion sensor technology could be applied to specifically detect bromide anions in drinking water. The IEFACP project deliverables are expected to attract both European and international academic and commercial interest. Implementation of this technology offers health applications as molecular switches, for example and sensors in environmental monitoring, improving the quality of life of European citizens. For future research, the project has secured a European Research Council advanced grant for the design of novel heteroditopic receptor molecules to be applied in high contrast magnetic resonance imaging.