High nuclearity polymetallic grids and clusters- towards functional molecule based devices

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Self-assembly methods with 'pre-programmed' ligands (molecules capable of binding metal ions to form a larger metal containing aggregate) are used to produce specific transition metal cluster and grid arrays with the metal ions bridged in close proximity by small atomic entities, which allow electronic communication between the metal centres. This leads to novel electrochemical and magnetic properties, which are being examined in the context of using these nano-meter scale, 'quantum dot' like arrays as devices for information storage and processing at the molecular level. The application of such systems to surfaces (e.g. gold, graphite) in ordered arrangements and monolayers, and the ability to probe individual molecules, and metal atoms, using scanning tunneling techniques (e.g. STM - scanning tunneling microscopy, STS - scanning tunneling spectroscopy and CITS - current induced tunneling spectroscopy), has paved the way for individual molecular switching using external electronic and magnetic probes, and the possible storage of information at both the molecular and surface array level. Current [nxn] grids include [2x2], [3x3] and [4x4] systems, thus creating nanometer (2-3 x 2-3 nm) scale molecules with very high metal and unpaired electron densities. Metals examined include Mn, Fe, Co, Ni, Cu, Zn. Attempts are underway to increase grid dimensions further with appropriate ligand design.