Molecular machines get a boost from a receptor that mimics logic gates by binding to both positive and negative ions. 

Paul Beer and colleagues at the University of Oxford, UK, have made a complex based on a calix[4]diquinone unit that selectively binds to cation-anion ion-pairs instead of individual ions. While receptors that bind anions and cations respectively are well known, receptors capable of binding both are rare.

 

                         

 

Beer was motivated to investigate the receptors because of the range of applications they offer. 'The selective binding of ion-pairs opens up the possibility for new systems designed for the selective extraction, transport or detection of relevant ion-pairs, such as those found in waste streams,' he said.

 The receptor also behaves in a manner consistent with AND logic (binding is only possible when both a suitable cation and anion are present), creating potential for application in constructing molecular machine devices. 

Beer now hopes to develop sensors based on this molecule to detect ion pairs. He aims to explore how this receptor could be used in ion-pair extraction and as a membrane transport agent. 'This receptor motif should be amenable for biological transportation purposes, allowing the movement of intact ion-pair species across membranes, and, more generally, for drug delivery purposes,' he said.

Sarah M Corcoran