Nanometre-sized polyhedral chemical architectures can form from combinations of transition metal cations and multifunctional ligands. These are often hollow and provide a confined chemical space where other molecules can bound or trapped. Hence many of these systems are being developed as nano-scale vessels for chemical entrapment, signalling and sensors, and even as tiny reaction vessels. We use the host molecule cyclotriveratrylene (CTV) as a ligand platform as its relatively rigid pyramidal shape lends itself to the formation of cage-like species. We have developed a library of several dozen functionalised CTV-ligands and have used these to generate a series of discrete metallo-cages with a spiked or “star-burst” shape. Highlights inlcude a family of Pd6L8 stella octangula assemblies, unusual topological complexity in triply interpenetrating catenanes, and the “Solomon’s cube” Pd4L4 assembly which exhibits a type of self-entanglement hitherto unreported in chemistry. We have recently developed a series of smaller metallo-cryptophanes with bis-carbene co-ligands which hold particular promise for host-guest binding behaviour, and act as crystalline sponges in the solid state. Different projects are possible, for example in: (i) development of functional metallo-cryptophanes for applications such as molecular recognition, chemical sensors or catalysis; (ii) development of new types of chemical topologies and metallo-cages and an investigation of their host-guest chemistries; (iii) development of stimuli-responsive metallo- and organic cages which can change shape or composition with a physical or chemical trigger. Project work will involve multi-step organic synthesis of ligands; synthetic coordination chemistry; investigations of the self-assembly behaviour of metallo-cages, and their solution characterisation using mass spectrometry and NMR; all aspects of single crystal X-Ray structure determination; and studies of the host-guest chemistry of the cages by techniques such as NMR, ITC, gas binding etc. Other characterisation methods that we employ include IR, fluorescence spectroscopy, thermal techniques (DSC, TGA) and electron microscopy where appropriate.
"Metallo-cryptophanes decorated with bis-N-heterocyclic carbene ligands: self-assembly and guest uptake into a non-porous crystalline lattice", J. J. Henkelis, C. J. Carruthers, S. E. Chambers, R. Clowes, A. I. Cooper, J. Fisher, M. J. Hardie, J. Am. Chem. Soc. 2014, 136, 14393-14396.
“Solvent-dependent chiral self-sorting, and stoichiometric speciation control of metallo-supramolecular cages”, J. J. Henkelis, J. Fisher, S. L. Warriner, M. J. Hardie, Chem. Eur. J., 2014, 20, 4117-4125.
“M3L2 metallo-cryptophanes: catenane and simple cages”, J. J. Henkelis, T. K. Ronson, L. P. Harding and M. J. Hardie, Chem. Commun., 2011, 47, 6560-6562
“Stellated polyhedral assembly of a topologically complicated Pd4L4 ‘Solomon cube’”, T. K. Ronson, J. Fisher, L.P. Harding, P. J. Rizkallah, J. E. Warren,. M. J. Hardie, Nature Chemistry, 2009, 1, 212-216.