Photoresponsive Metallo-Cages and Metallo-Supramolecular Assemblies

This thesis is concerned with the design and study of supramolecular architectures bearing photoresponsive groups, enabling specific properties and functions to be controlled with the use of light. Such systems have many potential applications in sensing, molecular recognition and stimuli responsive materials. All of the systems presented in this thesis are cage compounds containing a tripodal ligand scaffold based upon cyclotriveratrylene. The cyclotriveratrylene based ligands were functionalised with photo-responsive azobenzene groups. Self-assembly with rationally designed metal complexes furnished a library of M3L2 metallo-cryptophanes. The self-assembly behaviour of iridium(III), rhodium(III), palladium(II) and platinum (II) complexes with the ligands has been investigated using a range of solution-state techniques. The photoresponsive properties of the palladium cages have been investigated. The system can be switched between a trans/cis conformation by irradiation with an appropriate wavelength of light. The structural transformation results in a change in the volume of the internal cavity, enabling applications requiring modulation of the host-guest properties of the cage through the use of light. The host-guest properties of the palladium cages have also been assessed and found to bind a substituted napthalamide derivative as well as sodium alkyl sulphates. A detailed analysis of the binding of the sodium alkyl sulphates has been performed and association constants have been calculated. A discussion detailing the possible formation of a large coordination cage bearing the general formula M6L8 is also included. Spectroscopic and crystallographic data supporting this hypothesis is presented herein.