Functionalisable metallo-cages as nano-vessels

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In this proposal we will be investigating the self-assembly of metallo-supramolecular species and their use as post-construction vessels for chemical space applications. Utilisation of chemical space will ultimately address a variety of important objectives including creation of nano-scale vessels akin to artificial enzymes for performing unusual organic chemistry including catalytic transformations, and organising biologically relevant molecules in an artificial environment. The final area will give important information regarding the fundamental nature of the interactions between biological molecules, which may facilitate modelling studies, and may offer a new route to investigating more complex, higher order, structural motifs. We will be utilising molecular dynamics simulations to better understand the behaviour of guest molecules inside the metallo-cages, and to inform the design of the subsequent generation of functional cages.Self-assembly involves molecular or ionic components ("building blocks") arranging themselves into more complicated assemblies through reversible interactions between them. Self-assembled systems have well-defined architectures and geometric and interactional design of the building blocks can be used to promote formation of desired assemblies. In this proposal we are targeting discrete hollow cage-like assemblies with significant internal space. In some instances, we will be functionalising the insides of these cages in order to promote functionality such as catalysis, and binding/ordering of guest molecules.The building blocks that we will be using include the pyramidal-shaped cyclotriveratrylenes (CTVs) which offer hydrophobic binding sites for guest molecules, and we will be developing a new class of folded tetrapodal ligands that can be easily functionalised. Furthermore, CTV derivatives are often chiral and are known to form topologically complicated metallo-supramolecular assemblies. A topologically complicated assembly is one which displays mechanical inter-linking or threading, for example.Many discrete cages exist in solution and we will be developing their use as nano-scale reaction vessels for performing chemical reactions on guest molecules included inside the cages. A chemical included inside a cage is in a different environment to one outside of a cage in free solvent, and hence will show different chemistry. This is due to both the restricted space inside a cage and the specific interactions between the cage host and chemical guest. We will be designing mixed-ligand cages that allow for different types of interactions with chemical guests, hence an enhanced ability to control spatial orientation, and therefore regio/stereo-chemistry of the guests. For example, the product distribution of 1,3-dipolar coupling reactions could be manipulated or altered through reaction in a confined space. Oxidative reactions using the cages as catalysts will also be investigated.The novelty of the cage environment will be demonstrated, in solution, by the (NMR) detection and characterisation of interactions between guest molecules, and guest/host molecules. To this end small biologically relevant systems such as complementary deoxydinucleotides sequences will be incorporated and their base-pairing monitored. A DNA tetramer (the i-motif) will be studied to probe the effect of, for example, molecular crowding in the cage. Latterly it will be of interest to note whether the chiral interiors impose any 'order' on the DNA systems, permitting dipole-dipole couplings to be measured and analysed structurally. Such measurements are generally only accessible through the use of ordered media, such as lipids, and provide structural data not otherwise available from solution phase studies.