Heteroditopic Calixarene Based Receptors for Ion Pair Recognition and Mechanical Bond Assembly

This project aims to construct novel cyclic and interlocked 'host' molecules that are designed to simultaneously bind positively and negatively charged guest species within a single molecular host framework. Such multiple recognition site receptor systems have an exciting variety of potential uses as new extraction and membrane transport agents as well as having nanotechnological applications in sensing, switching and molecular machine-like behaviour.Using the 'bucket shaped' calix[4]arene molecule as a molecular scaffold the project begins with the covalent attachment of various cation and anion binding motifs onto this molecular framework to produce new cyclic heteroditopic receptors. Extensive inorganic ion-pair coordination studies will elucidate cooperative binding effects where a complexed cation will enhance the binding of an anion and vice-versa. Appropriately designed molecular cation-anion threading components, together with inorganic ion-pairs and neutral ligand threads will form interpenetrative assemblies with these ditopic host systems. Building on these pseudo-rotaxane assembly investigations, target interlocked chain-like catenane molecular structures will be synthesised using ion-pair templation synthetic methodologies and their ion-pair binding properties and chemically or electrochemically induced switchable rotational molecular movement investigated. The surface assembly of these interlocked catenane systems will lead to novel interfaces whose chemical characteristics may be modulated by switchable chemical and/or electrochemical control where rotational molecular movement exposes hydrophilic charged and hydrophobic neutral groups of the surface confined catenane systems. An attempt will be made to drive ( write ) this switching at molecular scales of spatial resolution and to subsequently read induced changes by proximal probe methods.