Ultrafast Electron Transfer in Supramolecular Mixed Valence Complexes

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This award to Professor Kubiak of the University of California, San Diego funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry focuses on ultrafast chemical reactions; those that occur in one-trillionth of a second (1 picosecond) over large supramolecular structures. These reactions involve the transfer of electrons over reasonably long distances, from 1 to 4 nanometers. The project builds on (1) the observation that exchanging electrons across hydrogen bonds can increase the strength of typically weak interactions; and (2) the observation of mixed valence nanoclusters. The latter are complex molecular structures composed of ruthenium clusters which transfer charge through attached metallic and semiconducting nanoparticles. The research will be extended to more complex systems in order to elucidate how electrons and electron transfer rates respond to different types of pathways through new supramolecular materials. Given the ability to easily manipulate the chemical compositions of these complex systems synthetically, Professor Kubiak and his team are able to custom design these assemblies for a variety of applications. In order to explore these intricate structures, the researchers first aim to stabilize the complexes by increasing the strength of their weak interactions (such as hydrogen bonds) and to then analyze the ultrafast electron transfer properties in these newly stabilized complexes via spectroscopic methods designed for this purpose. The research is relevant to both the scientific and engineering communities in their quest to develop new generations of molecular electronic devices. The future of such devices is dependent on the development of molecular complexes with two or more stable states, which can be switched between these states with extremely fast reaction times.